Evidence-Based Complementary and Alternative Medicine

Evidence-Based Complementary and Alternative Medicine / 2017 / Article

Review Article | Open Access

Volume 2017 |Article ID 4517971 | 92 pages | https://doi.org/10.1155/2017/4517971

Commercial Essential Oils as Potential Antimicrobials to Treat Skin Diseases

Academic Editor: Pinarosa Avato
Received21 Jul 2016
Accepted09 Oct 2016
Published04 May 2017


Essential oils are one of the most notorious natural products used for medical purposes. Combined with their popular use in dermatology, their availability, and the development of antimicrobial resistance, commercial essential oils are often an option for therapy. At least 90 essential oils can be identified as being recommended for dermatological use, with at least 1500 combinations. This review explores the fundamental knowledge available on the antimicrobial properties against pathogens responsible for dermatological infections and compares the scientific evidence to what is recommended for use in common layman’s literature. Also included is a review of combinations with other essential oils and antimicrobials. The minimum inhibitory concentration dilution method is the preferred means of determining antimicrobial activity. While dermatological skin pathogens such as Staphylococcus aureus have been well studied, other pathogens such as Streptococcus pyogenes, Propionibacterium acnes, Haemophilus influenzae, and Brevibacterium species have been sorely neglected. Combination studies incorporating oil blends, as well as interactions with conventional antimicrobials, have shown that mostly synergy is reported. Very few viral studies of relevance to the skin have been made. Encouragement is made for further research into essential oil combinations with other essential oils, antimicrobials, and carrier oils.

1. Introduction

The skin is the body’s largest mechanical barrier against the external environment and invasion by microorganisms. It is responsible for numerous functions such as heat regulation and protecting the underlying organs and tissue [1, 2]. The uppermost epidermal layer is covered by a protective keratinous surface which allows for the removal of microorganisms via sloughing off of keratinocytes and acidic sebaceous secretions. This produces a hostile environment for microorganisms. In addition to these defences, the skin also consists of natural microflora which offers additional protection by competitively inhibiting pathogenic bacterial growth by competing for nutrients and attachment sites and by producing metabolic products that inhibit microbial growth. The skin’s natural microflora includes species of Corynebacterium, staphylococci, streptococci, Brevibacterium, and Candida as well as Propionibacterium [38].

In the event of skin trauma from injuries such as burns, skin thinning, ulcers, scratches, skin defects, trauma, or wounds, the skin’s defence may be compromised, allowing for microbial invasion of the epidermis resulting in anything from mild to serious infections of the skin. Common skin infections caused by microorganisms include carbuncles, furuncles, cellulitis, impetigo, boils (Staphylococcus aureus), folliculitis (S. aureus, Pseudomonas aeruginosa), ringworm (Microsporum spp., Epidermophyton spp., and Trichophyton spp.), acne (P. acnes), and foot odour (Brevibacterium spp.) [3, 811]. Environmental exposure, for example, in hospitals where nosocomial infections are prominent and invasive procedures make the patient vulnerable, may also create an opportunity for microbial infection. For example, with the addition of intensive therapy and intravascular cannulae, S. epidermidis can enter the cannula and behave as a pathogen causing bloodborne infections. Noninfective skin diseases such as eczema can also result in pathogenic infections by damaging the skin, thus increasing the risk of secondary infection by herpes simplex virus and/or S. aureus [5, 8, 12].

Skin infections constitute one of the five most common reasons for people to seek medical intervention and are considered the most frequently encountered of all infections. At least six million people worldwide are affected by chronic wounds and up to 17% of clinical visits are a result of bacterial skin infections and these wounds are a frequent diagnosis for hospitalised patients. These are experienced daily and every doctor will probably diagnose at least one case per patient. Furthermore, skin diseases are a major cause of death and morbidity [8, 13, 14]. The healing rate of chronic wounds is affected by bacterial infections (such as S. aureus, E. coli, and P. aeruginosa), pain, inflammation, and blood flow, and thus infection and inflammation control may assist in accelerating healing [1517].

Topical skin infections typically require topical treatment; however, due to the ability of microbes to evolve and due to the overuse and incorrect prescribing of the current available conventional antimicrobials, there has been emergence of resistance in common skin pathogens such as S. aureus resulting as methicillin-resistant Staphylococcus aureus (MRSA) and other such strains. Treatment has therefore become a challenge and is often not successful [8, 18, 19]. In some regions of the world, infections are unresponsive to all known antibiotics [20]. This threat has become so severe that simple ulcers now require treatment with systemic antibiotics [21]. A simple cut on the finger or a simple removal of an appendix could result in death by infection. The World Health Organization (WHO) has warned that common infections may be left without a cure as we are headed for a future without antibiotics [22]. Therefore, one of the solutions available is to make use of one of the oldest forms of medicine, natural products, to treat skin infections and wounds [18, 23].

Complementary and alternative medicines (CAMs) are used by 60–80% of developing countries as they are one of the most prevalent sources of medicine worldwide [2427]. Essential oils are also one of the most popular natural products, with one of their main applications being for their use in dermatology [2830]. In fact, of all CAMs, essential oils are the most popular choice for treating fungal skin infections [13, 31]. Their use in dermatology, in the nursing profession, and in hospitals has been growing with great popularity worldwide, especially in the United States and the United Kingdom [1, 27, 3235]. Furthermore, the aromatherapeutic literature [1, 2, 26, 32, 3643] identifies numerous essential oils for dermatological use, the majority of which are recommended for infections. This brought forth the question as to the efficacy of commercial essential oils against the pathogens responsible for infections. The aim of this review was to collect and summarise the in vivo, in vitro, and clinical findings of commercial essential oils that have been tested against infectious skin diseases and their pathogens and, in doing so, offer aromatherapists and dermatologists valuable information regarding the effectiveness of essential oils for dermatological infections.

The readily available aromatherapeutic literature has reported over 90 (Table 1) commercial essential oils that may be used for treating dermatological conditions [1, 2, 26, 32, 3643]. An overview of the skin related uses can be seen in Figure 1. Essential oils are mostly used for the treatment of infections caused by bacteria, fungi, or viruses (total 62%). This is followed by inflammatory skin conditions (20%) such as dermatitis, eczema, and lupus and then general skin maintenance (18%) such as wrinkles, scars, and scabs, which are the third most common use of essential oils. Other applications include anti-inflammatory and wound healing applications (Figure 1). Of the 98 essential oils recommended for dermatological use, 88 are endorsed for treating skin infections. Of these, 73 are used for bacterial infections, 49 specifically for acne, 34 for fungal infections, and 16 for viral infections.

Scientific nameCommon nameDermatological useReference

Abies balsameaBalsam (Peru, Canadian), cracks, cuts, eczema, rashes, sores, and wounds[32]

Abies balsameaFirSkin tonic[36]

Acacia dealbataMimosaAntiseptic, general care, oily conditions, and nourisher[2, 32]

Acacia farnesianaCassieDry or sensitive conditions[32]

Achillea millefoliumYarrowAcne, burns, chapped skin, cuts, dermatitis, eczema, healing agent, infections, inflammation, oily conditions, pruritus, rashes, scars, toner, sores, ulcers, and wounds[32, 36, 40, 42]

Allium sativumGarlicAcne, antiseptic, fungal infections (ringworm), lupus, septic wounds, and ulcers[32, 36]

Amyris balsamiferaAmyrisInflammation[36]

Anethum graveolensDillWound healing encouragement[36]

Angelica archangelicaAngelicaCongested and dull conditions, fungal infections, inflammation, psoriasis, and tonic[32, 36]

Aniba rosaeodoraRosewoodAcne, congested conditions, cuts, damaged skin, dermatitis, general care, greasy and oily conditions, inflammation, psoriasis, scars, regeneration, sores, wounds, and wrinkles[2, 32, 36, 37, 39, 41, 42]

Anthemis nobilisRoman chamomileAbscesses, acne, allergies, antiseptic, blisters, boils, burns, cleanser, cuts, dermatitis, eczema, foot blisters, general care, herpes, inflammation, insect bites and stings, nappy rash, nourisher, problematic skin, pruritus, psoriasis, rashes, rosacea, sores, sunburn, ulcers, and wounds[2, 26, 32, 3643]

Apium graveolensCeleryReducing puffiness and redness[36]

Artemisia dracunculusTarragonInfectious wounds[36]

Betula albaBirch (white)Congested conditions, dermatitis, eczema, psoriasis, and ulcers[32, 36]

Boswellia carteriFrankincense/olibanumAbscesses, acne, aged or dry and damaged complexions, antiseptic, bacterial infections, blemishes, carbuncles, dermatitis, disinfectant, eczema, fungal and nail infections, general care, healing agent, inflammation, oily conditions, psoriasis, problematic conditions, regeneration or rejuvenation, scars, sores, toner, tonic, ulcers, wounds, and wrinkles[1, 2, 32, 3643]

Bursera glabrifoliaLinaloe (copal)Acne, conditioning, cuts, dermatitis, sores, and wounds[32, 40]

Calendula officinalisMarigoldAthlete’s foot, burns, cuts, diaper rash, eczema, fungal infections, inflammation, oily and greasy conditions, and wounds[26, 32, 39]

Cananga odorataYlang-ylangAcne, balancing sebum, dermatitis, eczema, general care, greasy and oily conditions, insect bites, and toner[2, 32, 3638, 40, 42, 43]

Canarium luzonicumElemiAged and dry complexions, bacterial infections, balancing sebum, cuts, fungal infections, inflammation, sores, ulcers, wounds, and wrinkles[32, 36, 40]

Carum carviCarawayAcne, boils, infected wounds, oily conditions, and pruritus[36]

Cedrus atlanticaCedar woodAcne, antiseptic, , cellulite, cracked skin, dandruff, dermatitis, eczema, eruptions, fungal infections, general care, genital infections, greasy and oily conditions, inflammation, insect bites and stings, psoriasis, scabs, and ulcers[1, 2, 32, 3639, 4143]

Cinnamomum camphoraCamphor (white)Acne, burns, inflammation, oily conditions, spots, and ulcers[32, 36, 42]

Cinnamomum zeylanicumCinnamonAntiseptic, gum and tooth care, warts, and wasp stings[32, 36, 37, 41, 42]

Cistus ladaniferRock rose/Cistus/labdanumAged complexion, bacterial infections, bedsores, blocked pores, eczema, oily conditions, sores, ulcers, varicose ulcers, wounds, and wrinkles[2, 32, 40]

Citrus aurantifoliaLimeAcne, bacterial infections, boils, cellulite, congested or greasy and oily conditions, cuts, insect bites, pruritus, tonic, sores, ulcers, warts, and wounds[2, 32, 36, 4043]

Citrus aurantium var. amaraNeroliAcne, aged and dry complexions, antiseptic, broken capillaries, cuts, dermatitis, eczema, general care, healing agent, psoriasis, scars, stretch marks, toner, tonic, thread veins, wounds, and wrinkles[2, 26, 32, 3643]

Citrus aurantium var. amaraPetitgrainAcne, antiseptic, bacterial infections, balancing sebum, blemishes, greasy and oily conditions, ∗∗ hyperhidrosis, pimples, pressure sores, sensitive complexions, toner, tonic, and wounds[1, 2, 32, 36, 37, 3942]

Citrus bergamiaBergamotAbscesses, acne, antiseptic, athlete’s foot, bacterial infections, blisters, boils, cold sores, deodorant, dermatitis, eczema, fungal infections, greasy and oily conditions, healing agent, inflammation, insect bites, pruritus, psoriasis, shingles, ulcers, viral infections (chicken pox, herpes, and shingles), and wounds[2, 26, 32, 36, 37, 4043]

Citrus limonLemonAbscesses, acne, antiseptic, athlete’s foot, blisters, boils, cellulite, corns, cuts, grazes, greasy and oily conditions, insect bites, mouth ulcers, rosacea, sores,ulcers, viral infections (cold sores, herpes, verrucae,and warts), and wounds[1, 2, 26, 32, 36, 37, 39, 4143]

Citrus paradisiGrapefruitAcne, antiseptic, cellulite improvement, cleanser, combination and problematic skin, congested and oily conditions, stretch marks, and toner[1, 2, 32, 36, 37, 3943]

Citrus reticulataMandarinAcne, cellulite, congested and oily conditions, general care, healing agent, scars, stretch marks, and toner[1, 32, 3638, 40, 43]

Citrus sinensisOrangeAcne, blocked pores, congested and oily conditions, dermatitis, dry and dull complexions, problematic skin, ulcers, and wrinkles[1, 32, 3638, 4043]

Citrus tangerinaTangerineAcne, chapped skin, inflammation, oily conditions, rashes, stretch marks, and toner[36, 40, 42]

Commiphora myrrhaMyrrhAcne, antiseptic, athlete’s foot, bacterial infections, bedsores, boils, cracked skin, cuts, dermatitis, eczema, fungal infections (athlete’s foot, ringworm), healing agent, inflammation, scars, sores, ulcers, weeping wounds, and wrinkles[1, 2, 26, 32, 3643]

Coriandrum sativumCorianderUsed to prevent the growth of odour causing bacteria[37]

Cupressus sempervirensCypressAcne, blocked pores, bromodosis, cellulite, cellulitis, deodorant, hyperhidrosis, oily conditions, rashes, rosacea, and wounds[1, 2, 32, 3638, 4043]

Curcuma longaTurmericCuts, sores, and wounds[40]

Cymbopogon citratusLemongrassAcne, athlete’s foot, bacterial infections, blocked or open pores, cellulite, fungal infections, hyperhidrosis, oily conditions, and toner[2, 32, 36, 37, 41, 42]

Cymbopogon martiniiPalmarosaAcne, bacterial infections, balancing sebum, damaged and dry complexions, dermatitis, eczema, fungal infections, oily conditions, pressure sores, psoriasis, scars, toner, tonic, sores, wounds, and wrinkles[2, 32, 3642]

Cymbopogon nardusCitronellaBromodosis, hyperhidrosis, oily conditions, and softener[32, 36, 42]

Daucus carotaCarrot seedAged and dry complexions, carbuncles, dermatitis, eczema, inflammation, oily conditions, pruritus, psoriasis, rashes, scarring, toner, ulcers, vitiligo, weeping sores, wounds, and wrinkles[2, 32, 36, 40, 42]

Dryobalanops aromaticaBorneol (Borneo Camphor)Cuts and sores[32]

Eucalyptus globulusEucalyptusAbscesses, antiseptic, athlete’s foot, bacterial dermatitis, bacterial infections, blisters, boils, burns, chicken pox, cleanser, congested conditions, cuts, fungal infections, general infections, herpes (cold sores), inflammation, insect bites, shingles, sores, ulcers, and wounds[1, 26, 32, 3639, 4143]

Syzygium aromaticumCloveAcne, antiseptic, athlete’s foot, burns, cuts, cold sores, fungal infections, lupus, sores, septic ulcers, and wounds[32, 36, 37, 41, 42]

Ferula galbanifluaGalbanumAbscesses, acne, blisters, boils, cuts, inflammation, scar tissue improvement, toner, and wounds[32, 36]

Foeniculum dulceFennelAged and wrinkled complexions, bromodosis, cellulite, cellulitis, congested, greasy, and oily conditions, cleanser, and tonic[1, 32, 36, 37, 4043]

Guaiacum officinaleGuaiacwoodFirming or tightening the skin[36]

Helichrysum italicumImmortelle/everlasting/HelichrysumAbscesses, acne, athlete’s foot, bacterial infections, boils, blisters, cell regeneration, cuts, damaged skin conditions, dermatitis, eczema, fungal infections (ringworm), inflammation, psoriasis, rosacea, scars, sores, ulcers, and wounds[2, 32, 36, 40, 41]

Humulus lupulusHopsDermatitis, ulcers, rashes, and nourisher[32]

Hyssopus officinalisHyssopCuts, dermatitis, eczema, healing agent, inflammation, scars, sores, and wounds[32, 36, 41]

Jasminum officinaleJasmineAged and dry complexions, general care, inflammation, revitalization, oily conditions, and psoriasis[2, 26, 32, 36, 37, 40]

Juniperus virginianaJuniperAcne, antiseptic, blocked pores, cellulite, congested and oily conditions, deodorant, eczema, dermatitis, general care, general infections, psoriasis, toner, ulcers, weeping eczema, and wounds[1, 2, 32, 36, 37, 39, 4143]

Juniperus oxycedrusCadeCuts, dermatitis, eczema, sores, and spots[32]

Kunzea ericoidesKānukaAthlete’s foot[40]

Laurus nobilisBayAcne, fungal infections, inflammation, oily conditions, pressure sores, and varicose ulcers[32, 36, 41]

Lavandula angustifoliaLavenderAbscesses, acne, antiseptic, bacterial infections, blisters, boils, burns, carbuncles, cellulite, congested and oily conditions, cuts, deodorant, dermatitis, eczema, foot blisters, fungal infections (athlete’s foot, ringworm), general care, healing agent, inflammation, insect bites and stings, pressure sores, pruritus, psoriasis, rosacea, scalds, scarring, sores, sunburn, ulcers,viral infections (chicken pox, cold sores, shingles,and warts), and wounds[2, 26, 32, 3643]

Lavandula flagransLavandinAcne, abscesses, boils, blisters, congested conditions, cuts, eczema, healing agent, inflammation, insect bites and stings, pressure sores, scalds, sores, and wounds[32, 36, 41]

Lavandula spicaLavender spikeAbscesses, acne, bacterial infections, blisters, boils, burns, congested and oily conditions, cuts, dermatitis, eczema, inflammation, fungal infections (athlete’s foot, ringworm), pressure sores, psoriasis, sores, ulcers, and wounds[32, 36, 41]

Leptospermum scopariumManukaAcne, cuts, fungal infections (athlete’s foot, ringworm), ulcers, and wounds[2, 40]

Verbena officinalisVerbenaCongested conditions and nourisher[36]

Liquidambar orientalisSweetgumCuts, ringworm, sores, and wounds[32]

Litsea cubebaMay ChangAcne, dermatitis, greasy and oily conditions, and hyperhidrosis[32, 36]

Melaleuca alternifoliaTea treeAbrasions, abscesses, acne, antiseptic, bacterial infections, blemishes, blisters, boils, burns, carbuncles, cuts, dandruff, fungal infections (athlete’s foot, nails, ringworm, and tinea), inflammation, insect bites, oily conditions, rashes, sores, spots, sunburn, ulcers, viral infections (cold sores, chicken pox, herpes, shingles,and warts), and wounds[1, 2, 26, 32, 3643]

Melaleuca cajuputi CajuputAcne, insect bites, oily conditions, psoriasis, and spots[32, 36, 42]

Melaleuca viridifloraNiaouli/GomenolAbscesses, acne, antiseptic, bacterial infections, blisters, boils, burns, chicken pox, congested and oily conditions, cuts, eruptions, healing agent, insect bites, psoriasis, sores, ulcers, and wounds[2, 32, 36, 3942]

Melissa officinalisMelissa/lemon balmAllergic reactions, cold sores, eczema, fungal infections, inflammation, insect stings, ulcers, and wounds[1, 26, 32, 36, 41, 42]

Mentha piperitaPeppermintAcne, antiseptic, blackheads, chicken pox, congested and greasy conditions, dermatitis, inflammation, pruritus, ringworm, scabies, softener, toner, and sunburn[1, 2, 32, 36, 37, 4143]

Mentha spicataSpearmintAcne, congested conditions, dermatitis, pruritus, scabs, and sores[32, 36, 39, 42]

Myristica fragransNutmegHair conditioner[36]

Myrocarpus fastigiatusCabreuvaCuts, scars, and wounds[32]

Myrtus communisMyrtleAcne, antiseptic, blemishes, blocked pores, bruises, congested and oily conditions, and psoriasis[2, 32, 36, 40]

Nardostachys jatamansiSpikenardEczema, inflammation, psoriasis, and sores[32, 40]

Ocimum basilicumBasilAcne, antiseptic, congested conditions, insect bites, and wasp stings[1, 36, 37, 39, 40, 42]

Origanum majoranaMarjoramBruises and fungal infections[32, 36]

Origanum vulgareOreganoAthlete’s foot, bacterial infections, cuts, eczema, fungal infections, psoriasis, warts, and wounds[36, 41]

Pelargonium odoratissimumGeraniumAcne, aged and dry complexions, bacterial infections, balancing sebum, burns, cellulite, chicken pox, congested and oily conditions, cracked skin, cuts, dermatitis, deodorant, eczema, fungal infections (athlete’s foot, ringworm), general care, healing agent, herpes, impetigo, inflammation, measles, psoriasis, rosacea, shingles, problematic skin, sores, ulcers, and wounds[2, 26, 32, 3643]

Pelargonium roseumRose geraniumAging and dry or wrinkled skin[40]

Petroselinum sativumParsleyBruises, scalp conditioning, and wounds[36]

Pimpinella anisumAniseInfectious diseases[36]

Pinus sylvestrisPineAntiseptic, bromodosis, congested conditions, cuts, eczema, hyperhidrosis, pruritus, psoriasis, and sores[32, 36, 37, 4143]

Piper nigrumBlack pepperBruises and fungal infections[36, 42]

Pistacia lentiscusMasticAbscesses, blisters, boils, cuts, ringworm, and wounds[32]

Pistacia palaestinaTerebinthAbscesses, blisters, boils, cuts, infectious wounds, ringworm, and sores[32, 36]

Pogostemon patchouliPatchouliAbscesses, acne, chapped or damaged and cracked skin, dermatitis, cold sores, eczema, fungal infections (athlete’s foot), general care, healing agent, impetigo, inflammation, oily conditions, pruritus, scalp disorders, scars, sores, tonic, stretch marks, and wounds[1, 2, 32, 3643]

Rosa damascenaRose ottoAging and dry conditions, bacterial infections, eczema, inflammation, toner, tonic, and wounds[2, 3841]

Rosa gallicaRoseBroken capillaries, cuts, dry and aging conditions, burns, eczema, healing agent, inflammation, pruritus, psoriasis, scars, toner, tonic, stretch marks, sunburn, thread veins, and wrinkles[26, 32, 3638, 42, 43]

Rosmarinus officinalisRosemaryAcne, bacterial infections, balancing sebum, cellulite, congested and oily conditions, dandruff, dermatitis, dry scalp, eczema, general care, and rosacea[1, 32, 36, 37, 39, 41, 42]

Salvia lavandulifoliaSpanish sageAcne, antiseptic, bacterial infections, cellulite, cold sores, cuts, dermatitis, deodorant, hyperhidrosis, oily conditions, psoriasis, sores, and ulcers[32, 36, 37, 41]

Salvia sclareaClary sageAbscesses, acne, balancing sebum, blisters, boils, cell regeneration, dandruff, dermatitis, greasy and oily conditions, hyperhidrosis of the feet, inflammation, ulcers, and wrinkles[1, 2, 32, 36, 40, 42]

Santalum albumSandalwoodAcne, antiseptic, bacterial infections, boils, burns, chapped or damaged and dry conditions, eczema, fungal infections, general care, greasy and oily conditions, inflammation, pruritus, sunburn, and wounds[1, 2, 26, 32, 3639, 4143]

Santolina chamaecyparissusSantolinaInflammation, pruritus, ringworm, scabs, verrucae, and warts[36]

Styrax benzoin BenzoinCracks, cuts, dermatitis, eczema, healing, inflammation, injured and irritated conditions, pruritus, sores, and wounds[1, 2, 32, 36, 40, 42]

Tagetes minutaTagetesBacterial infections, fungal infections, inflammation, and viral infections (verrucae and warts)[32, 36, 42]

Thymus vulgarisThymeAbscesses, acne, antiseptic, blisters, burns, carbuncles, cellulitis, cuts, deodorant, dermatitis, eczema, fungal infections, oily conditions, sores, and wounds[1, 32, 36, 37, 41, 42]

Tilia europaeaLinden BlossomBlemishes, burns, freckles, softener, tonic, and wrinkles[36]

Vetiveria zizanioides VetiverAcne, antiseptic, balancing sebum, cuts, eczema, malnourished and aging skin, oily conditions, weeping sores, and wounds[1, 2, 32, 36, 37, 41, 42]

Viola odorataVioletAcne, bruises, congested and oily conditions, eczema, inflammation, infections, ulcers, and wounds[2, 32, 36, 40]

Zingiber officinaleGingerBruises, carbuncles, and sores[36]

Conditions involved in dermatological infections are shown in italics.
A medical condition that causes excessive sweating.

2. Materials and Methods

2.1. Searching Strategy/Selection of Papers

The aim of the comparative review was to identify the acclaimed dermatological commercial essential oils according to the aromatherapeutic literature and then compare and analyse the available published literature. This will serve as a guideline in selecting appropriate essential oils in treating dermatological infections. The analysed papers were selected from three different electronic databases: PubMed, ScienceDirect, and Scopus, accessed during the period 2014–2016. The filters used included either “essential oils”, “volatile oils”, or “aromatherapy” or the scientific or common name for each individual essential oil listed in Table 1 and the additional filters “antimicrobial”, “antibacterial”, “skin”, “infection”, “dermatology”, “acne”, “combinations”, “fungal infections”, “dermatophytes”, “Brevibacteria”, “odour”, “antiviral”, “wounds”, “dermatitis”, “allergy”, “toxicity”, “sentitisation”, or “phototoxicity”.

2.2. Inclusion Criteria

In order to effectively understand the possible implications and potential of essential oils, the inclusion criteria were broad, especially with this being the first review to collate this amount of scientific evidence with the aromatherapeutic literature. Inclusion criteria included the following:(i)Type of in vitro studies for bacterial and fungal pathogens by means of the microdilution assay, macrodilution assay, or the agar dilution assay(ii)In vivo studies(iii)Antiviral studies(iv)Case reports(v)Animal studies(vi)All clinical trials

2.3. Exclusion Criteria

Papers or pieces of information were excluded for the following reasons:(i)Lack of accessibility to the publication(ii)If the incorrect in vitro technique (diffusion assays) was employed(iii)Indigenous essential oils with no relevance to commercial oils(iv)If they were in a language not understood by the authors of the review(v)Pathogens studied not relevant to skin disease

2.4. Data Analysis

The two authors (Ané Orchard and Sandy van Vuuren) conducted their own data extraction independently, after which critical analysis was applied. Information was extrapolated and recorded and comments were made. Observations were made and new recommendations were made as to future studies.

3. Results

3.1. Description of Studies

After the initial database search, 1113 reports were screened. Duplicates were removed, which brought the article count down to 513, after which the abstracts were then read and additional reports removed based on not meeting the inclusion criteria. A final number of 349 articles were read and reviewed. Of these, 143 were in vitro bacterial and fungal studies (individual oil and 45 combinations), two in vivo studies, 15 antiviral studies, 19 clinical trials, and 32 toxicity studies. The process that was followed is summarised in Figure 2.

3.2. Experimental Approaches
3.2.1. Chemical Analysis

Essential oils are complex organic (carbon containing) chemical entities, which are generally made up of hundreds of organic chemical compounds in combination that are responsible for the essential oil’s many characteristic properties. These characteristics may include medicinal properties, such as anti-inflammatory, healing, or antimicrobial activities, but may also be responsible for negative qualities such as photosensitivity and toxicity [37].

Even with the high quality grade that is strived for in the commercial sector of essential oil production, it must be noted that it is still possible for essential oil quality to display discrepancies, changes in composition, or degradation. The essential oil composition may even vary between the same species [1, 44]. This may be due to a host of different factors such as the environment or location that the plants are grown in, the harvest season, which part of the plant was used, the process of extracting the essential oil, light or oxygen exposure, the storage of the oil, and the temperature the oil was exposed to [4551].

Gas chromatography in combination with mass spectrometry (GCMS) is the preferred technique for analysis of essential oils [52]. This is a qualitative and quantitative chemical analysis method which allows for the assurance of the essential oil quality through the identification of individual compounds that make up an essential oil [1, 45, 53]. It has clearly been demonstrated that there is a strong correlation between the chemical composition and antimicrobial activity [51, 54, 55]. Understanding the chemistry of essential oils is essential for monitoring essential oil composition, which then further allows for a better understanding of the biological properties of essential oils. It is recommended to always include the chemical composition in antimicrobial studies [56].

3.3. Antimicrobial Investigations

Several methods exist that may be employed for antimicrobial analysis, with two of the most popular methods being the diffusion and the dilution methods [5659].

3.3.1. Diffusion Method

There are two types of diffusion assays. Due to the ease of application, the disc diffusion method is one of the most commonly used methods [60]. This is done by applying a known concentration of essential oil onto a sterile filter paper disc. This is then placed onto agar which has previously been inoculated with the microorganism to be tested, or it is spread on the surface. If necessary, the essential oil may also be dissolved in an appropriate solvent. The other diffusion method is the agar diffusion method, where, instead of discs being placed, wells are made in the agar into which the essential oil is instilled. After incubation, antimicrobial activity is then interpreted from the zone of inhibition (measured in millimetres) using the following criteria: weak activity (inhibition zone ≤ 12 mm), moderate activity (12 mm < inhibition zone < 20 mm), and strong activity (inhibition zone ≤ 20 mm) [24, 6062].

Although this used to be a popular method, it is more suitable to antibiotics rather than essential oils as it does not account for the volatile nature of the essential oils. Essential oils also diffuse poorly through an aqueous medium as they are hydrophobic. Thus, the results are less reliable as they are influenced by the ability of the essential oil to diffuse through the agar medium, resulting in variable results, false negatives, or a reduction in antimicrobial activity [24, 63]. The results have been found to vary significantly when tested this way and are also influenced by other factors such as disc size, amount of compound applied to the disc, type of agar, and the volume of agar [57, 59, 6468]. It has thus been recommended that results are only considered where the minimum inhibitory concentration (MIC) or cidal concentration values have been established [65].

3.3.2. Dilution Methods

The dilution assays are reliable, widely accepted, and promising methods for determining an organism’s susceptibility to inhibitors. The microdilution method is considered the “gold standard” [64, 6870]. This is a quantitative method that makes it possible to calculate the MIC and allows one to understand the potency of the essential oil [68, 71]. With one of the most problematic characteristics of essential oils being their volatility, the microdilution technique allows for an opportunity to work around this problem as it allows for less evaporation due to the essential oil being mixed into the broth [67].

This microdilution method makes use of a 96-well microtitre plate under aseptic conditions where the essential oils (diluted in a solvent to a known concentration) are serially diluted. Results are usually read visually with the aid of an indicator dye. The microdilution results can also be interpreted by reading the optical density [72, 73]; however, the shortcoming of this method is that the coloured nature of some oils may interfere with accurate turbidimetric readings [74].

Activity is often classified differently according to the quantitative method followed. van Vuuren [56] recommended 2.00 mg/mL and less for essential oils to be considered as noteworthy, Agarwal et al. [75] regarded 1.00% and less, and Hadad et al. [76] recommended ≤250.00 μg/mL. On considering the collection of data and frequency of certain MIC values, this review recommends MIC values of ≤1.00 mg/mL as noteworthy.

The macrodilution method employs a similar method to that of the microdilution method, except that, instead of a 96-well microtitre plate being used, multiple individual test tubes are used. Although the results are still comparable, this is a time-consuming and a tedious method, whereas the 96-well microtitre plate allows for multiple samples to be tested per plate, allowing for speed, and it makes use of smaller volumes which adds to the ease of its application [77, 78]. The agar dilution method is where the essential oil is serially diluted, using a solvent, into a known amount of sterile molten agar in bottles or tubes and mixed with the aid of a solvent. The inoculum is then added and then the agar is poured into plates for each dilution and then incubated. The absence of growth after incubation is taken as the MIC [7981].

3.3.3. The Time-Kill Method

The time-kill (or death kinetic) method is a labour intensive assay used to determine the relationship between the concentration of the antimicrobial and the bactericidal activity [82]. It allows for the presentation of a direct relationship in exposure of the pathogen to the antimicrobial and allows for the monitoring of a cidal effect over time [74]. The selected pathogen is exposed to the antimicrobial agent at selected time intervals and aliquots are then sampled and serially diluted. These dilutions are then plated out onto agar and incubated at the required incubation conditions for the pathogen. After incubation, the colony forming units (CFU) are counted. These results are interpreted from a logarithmic plot of the amount of remaining viable cells against time [74, 82, 83]. This is a time-consuming method; however, it is very useful for deriving real-time exposure data.

3.4. Summary of Methods

The variation in essential oil test methods makes it difficult to directly compare results [24, 58]. Numerous studies were found to employ the use of a diffusion method due to its acclaimed “ease” and “time saving” ability of the application. Researchers tend to use this as a screening tool whereby results displaying interesting outcomes are further tested using the microdilution method [8487]. The shortcoming of this method is that firstly, due to the discussed factors affecting the diffusion methods, certain essential oils demonstrate no inhibition against the pathogen, and thus further studies with the oils are overlooked. Secondly, the active oils are then investigated further using the microdilution method. Therefore, the researchers have now doubled the amount of time required to interpret the quantitative data. Thirdly, the method may be believed to be a faster method if one considers the application; however, if one considers the preparation of the agar plates and their risk of contamination as well as the overall process of this method, there is very little saving of time and effort.

It is recommended to follow the correct guidelines as set out by the Clinical and Laboratory Standards Institute M38-A (CLSI) protocol [88] and the standard method proposed by the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antibiotic Susceptibility Testing (AFST-EUCAST) [89] for testing with bacteria and filamentous fungi.

Other factors that may affect results and thus make it difficult to compare published pharmacological results of essential oils are where data is not given on the chemical composition, the microbial strain number, temperature and length of incubation, inoculum size, and the solvent used. The use of appropriate solvents helps address the factor of poor solubility of essential oils. Examples include Tween, acetone, dimethylformamide (DMF), dimethylsulfoxide (DMSO), and ethanol. Tween, ethanol, and DMSO have, however, been shown to enhance antimicrobial activity of essential oils [24, 53, 90]. Soković et al. [91] tested antimicrobial activity with ethanol as the solvent and Tween. When the essential oils were diluted with Tween, it resulted in a greater antifungal activity; however, Tween itself does not display its own antimicrobial activity [92]. Eloff [93] identified acetone as the most favourable solvent for natural product antimicrobial studies.

The inoculum is a representative of the microorganisms present at the site of infection [94]. When comparing different articles, the bacterial inoculum load ranges from to  CFU/mL. The antibacterial activity is affected by inoculum size [62, 9599]. If this concentration is too weak, the effect of the essential oils strengthens; however, this does not allow for a good representation of the essential oil’s activity. If the inoculum is too dense, the effect of the essential oil weakens and the inoculum becomes more prone to cross contamination [100]. Future studies should aim to keep the inoculum size at the recommended  CFU/mL [99].

4. Pathogenesis of Wounds and Skin Infections and the Use of Essential Oils

The pathogenesis of the different infections that are frequently encountered in wounds and skin infections is presented in Table 2. A more in-depth analysis of essential oils and their use against these dermatological pathogens follows.

Skin diseaseAnatomical structure affected by infectionResponsible pathogensReference

Bacterial infections
AbscessesSkin and subcutaneous tissueStaphylococcus aureus; methicillin-resistant S. aureus (MRSA)[101]
AcneSebum glandsPropionibacterium acnes; S. epidermidis[8, 102]
ActinomycosisSkin and subcutaneous tissueActinomyces israelii[5]
Boils/carbuncles and furunclesHair folliclesS. aureus[8]
Bromodosis (foot odour)Epidermis/cutaneousBrevibacterium spp.; P. acnes[6, 103]
CellulitisSubcutaneous fatβ-Hemolyticstreptococci; S. aureus; MRSA[7, 8, 101]
EcthymaCutaneousS. aureus; Streptococcus pyogenes[7]
ErysipelasDermis, intradermalS. pyogenes[8]
ErythrasmaEpidermisCorynebacterium minutissimum[5]
FolliculitisHair folliclesS. aureus; MRSA[8, 101]
ImpetigoEpidermisS. pyogenes; S. aureus[8, 104, 105]
Periorbital cellulitisSubcutaneous fatHaemophilus influenzae[106]
Surgical woundsSkin, fascia, and subcutaneous tissueEscherichia coli; Enterococcus spp.; Pseudomonas aeruginosa; S. aureus[8]

Necrotizing infections
Necrotizing fasciitisSkin, fascia, subcutaneous tissue, and muscleS. pyogenes; anaerobic pathogens[5, 8, 107]
Gas forming infectionsSkin, subcutaneous tissue, and muscleGram-negative and various anaerobes[5]
Gas gangreneSkin, subcutaneous tissue, and muscleClostridium spp. (C. perfringens, C. septicum, C. tertium, C. oedematiens, and C. histolyticum)[5, 8, 107]

Fungal infections
Candidal infections (intertrigo, balanitis, nappy rash, angular cheilitis, and paronychia)Superficial skinCandida albicans[7]
EumycetomaSubcutaneous infectionMadurella mycetomatis[108]
Dermatophytosis (tinea pedis/athlete’s foot, tinea cruris, tinea capitis, tinea corporis, tinea manuum, and tinea unguium/onychomycosis)Keratin layer, epidermisDermatophytes (Microsporum, Epidermophyton, and Trichophyton spp.)[8]
Seborrheic dermatitisSubcutaneous infectionMalasseziafurfur[109]
Tinea/pityriasis versicolorSuperficial skinM. furfur[7, 110]

Viral infections
Herpes simplexMucocutaneous epidermidisHerpes simplex virus (HSV) type 1, orofacial disease; HSV type 2, genital infection [7]
Chicken poxMucocutaneous epidermidisVaricella zoster
Molluscum contagiosumPrickle cells of epidermidisPoxvirus
ShinglesMucocutaneous epidermidisHerpes zoster

Warts and verrucaeEpidermisHuman papillomavirus[5, 7]

4.1. Gram-Positive Bacteria

The Gram-positive bacterial cell wall is comprised of a 90–95% peptidoglycan layer that allows for easy penetration of lipophilic molecules into the cells. This thick lipophilic cell wall also results in essential oils making direct contact with the phospholipid bilayer of the cell membrane which allows for a physiological response to occur on the cell wall and in the cytoplasm [183, 184].

4.1.1. Staphylococcus aureus

Staphylococcus aureus is a common Gram-positive bacterium that can cause anything from local skin infections to fatal deep tissue infections. The pathogen is also found colonising acne and burn wounds [185187]. Methicillin-resistant S. aureus (MRSA) is one of the most well-known and widespread “superbugs” and is resistant to numerous antibiotics [158]. Methicillin-resistant S. aureus strains can be found to colonise the skin and wounds of over 63%–90% of patients and have been especially infamous as being the dreaded scourge of hospitals for several years [22, 188190]. Staphylococcus aureus has developed resistance against erythromycin, quinolones, mupirocin, tetracycline, and vancomycin [190192].

Table 3 shows some of the antimicrobial in vitro studies undertaken on commercial essential oils and additional subtypes against this most notorious infectious agent of wounds. Of the 98 available commercial essential oils documented from the aromatherapeutic literature for use for dermatological infections, only 54 oils have been tested against S. aureus and even fewer against the resistant S. aureus strain. This is troubling, especially if one considers the regularity of S. aureus resistance. It should be recommended that resistant S. aureus strains always be included with every study.

Essential Species Main Reference

Abies balsamea (fir/balsam)MICS. aureus (ATCC 6538)Acetone3.00 mg/mLβ-Pinene (31.00%), bornyl acetate (14.90%), δ-3-carene (14.20%)[99]

Abies holophylla (Manchurian fir)MICS. aureus (ATCC 25923)5% DMSO21.80 mg/mLBicyclo[2.2.1]heptan-2-ol (28.05%), δ-3-carene (13.85%), α-pinene (11.68%), camphene (10.41%) [111]
S. aureus (ATCC 6538)>21.80 mg/mL
Abies koreana (Korean fir)MICS. aureus (ATCC 25923)5% DMSO21.80 mg/mLBornyl ester (41.79%), camphene (15.31%), α-pinene (11.19%)
S. aureus (ATCC 6538)>21.80 mg/mL

Achillea millefolium (yarrow)MICS. aureus (ATCC 25923)Tween 8072.00 mg/mLEucalyptol (24.60%), camphor (16.70%), α-terpineol (10.20%)[112]

Achillea setacea (bristly yarrow)MICS. aureus (ATCC 25923)Tween 804.50 mg/mLSabinene (10.80%), eucalyptol (18.50%)[113]

Angelica archangelica (angelica), rootMICS. aureus (ATCC 6538)Acetone1.75 mg/mLα-Phellandrene (18.50%), α-pinene (13.70%), β-phellandrene (12.60%), δ-3-carene (12.1%) [99]
Angelica archangelica (angelica), seed2.00 mg/mLβ-Phellandrene (59.20%)

Anthemis aciphylla var. discoidea (chamomile), flowers MICS. aureus (ATCC 6538) DMSO1.00 mg/mLα-Pinene (39.00%), terpinen-4-ol (32.10%) [114]
Anthemis aciphylla var. discoidea (chamomile), aerial parts 0.50 mg/mLα-Pinene (49.40%), terpinen-4-ol (21.80%)
Anthemis aciphylla var. discoidea (chamomile), leavesTerpinen-4-ol (24.30%)

Anthemis nobilis (chamomile)MICS. aureus (ATCC 6538)Acetone16.00 mg/mL2-Methylbutyl-2-methyl propanoic acid (31.50%), limonene (18.30%), 3-methylpentyl-2-butenoic acid (16.70%), isobutyl isobutyrate (10.00%)[99]

Artemisia dracunculus (tarragon)MICS. aureus (ATCC 6538)Acetone3.00 mg/mLEstragole (82.60%)[99]

Backhousia citriodora (lemon myrtle)ADMS. aureus (NCTC 4163)Tween 200.05% v/vGeranial (51.40%), neral (40.90%) [115]
MRSA (clinical isolate)0.20% v/v

Boswellia carteri (frankincense) (9 samples) MICS. aureus (ATCC 12600) Acetone5.00–16.00 mg/mLα-Pinene (4.80–40.40%), myrcene (1.60–52.40%), limonene (1.90–20.40%), α-thujene (0.30–52.40%), p-cymene (2.70–16.90%), β-pinene (0.30–13.10%) [116]
Boswellia frereana (frankincense) (3 samples)4.00–12.00 mg/mLα-Pinene (2.00–64.70%), α-thujene (0.00–33.10%), p-cymene (5.40–16.90%)
Boswellia neglecta (frankincense)6.00 mg/mLNCR[117]
α-Pinene (43.40%), β-pinene (13.10%)[116]
Boswellia papyrifera (frankincense)1.50 mg/mLNCR [117]
Boswellia rivae (frankincense)2.50 mg/mL
Boswellia sacra (frankincense) (2 samples)4.00–8.00 mg/mLα-Pinene (18.30–28.00%), α-thujene (3.90–11.20%), limonene (11.20–13.10%) [116]
Boswellia spp. (frankincense) (4 samples)6.00–9.30 mg/mLα-Pinene (18.80–24.20%), limonene (11.70–19.00%)
Boswellia thurifera (frankincense)10.00 mg/mLα-Pinene (28.0%), limonene (14.6%)

Cananga odorata (ylang-ylang)MICS. aureus (ATCC 6538)Acetone2.00 mg/mLBicyclosesquiphellandrene (19.50%), β-farnesene (13.90%) [99]
Cananga odorata (ylang-ylang), heads4.00 mg/mLBenzyl acetate (31.90%), linalool (27.00%), methyl benzoate (10.40%)

Canarium luzonicum (elemi)MICS. aureus (ATCC 6538)Acetone3.00 mg/mLLimonene (41.90%), elemol (21.60%), α-phellandrene (11.40%)[99]

Carum carvi (caraway)MICS. aureus (ATCC 6538)Acetone2.00 mg/mLLimonene (27.60%), carvone (67.50%)[99]
S. aureusDMSO≤1.00 μg/mLDL-limonene (53.35%), β-selinene (11.08%), β-elemene (10.09%)[118]

Caryophyllus aromaticus (clove)ADM90S. aureus (ATCC 25923, 16 MRSA and 15 MSSA clinical isolates)Tween 802.70 mg/mLEugenol (75.85%), eugenol acetate (16.38%)[119]

Cinnamomum Cassia (cinnamon) MICS. aureus DMSO ≤1.00 μg/mLtrans-Caryophyllene (17.18%), eugenol (14.67%), [118]
Linalool L (14.52%), trans-cinnamyl acetate (13.85%), cymol (11.79%), cinnamaldehyde (11.25%)

Cinnamomum zeylanicum (cinnamon)MICS. aureus (ATCC 6538)Acetone2.00 mg/mLEugenol (80.00%)[99]
MICS. aureus (ATCC 25923)n.m.0.02 mg/mLNCR[85]
ADM10% DMSO3.20 mg/mL[80]
ADM90S. aureus (ATCC 25923, 16 MRSA and 15 MSSA clinical isolates)Tween 800.25 mg/mLCinnamaldehyde (86.31%)[119]

Citrus aurantifolia (lime)ADMS. aureus (ATCC 25923)10% DMSO12.80 mg/mLCinnamaldehyde (52.42%)[80]

Citrus aurantium (bitter orange), flowersMICS. aureus (ATCC 25923)50% DMSO0.31 mg/mLLimonene (27.50%), E-nerolidol (17.50%), α-terpineol (14.00%) [120]
MICS. aureus (ATCC 6536)0.63 mg/mL

Citrus aurantium (petitgrain)MICS. aureus (ATCC 6536)Acetone4.00 mg/mLLinalyl acetate (54.90%), linalool (21.10%)[99]

Citrus bergamia (bergamot)MACS. aureus (ATCC 6538)n.m.1.25 μL/mLBergamol (16.10%), linalool (14.02%), D-limonene (13.76%)[62]

Citrus grandis (grapefruit)MICS. aureus (ATCC 6538)Acetone3.00 mg/mLLimonene (74.80%)[99]

Citrus medica limonum (lemon)ADMS. aureus (ATCC 25923)10% DMSO>12.80 mg/mLNCR[80]
MICS. aureus (ATCC 6538)Acetone3.00 mg/mL[99]

Citrus sinensis (orange)ADMS. aureus (ATCC 25923)10% DMSO>12.80 mg/mL NCR[80]
MACS. aureus (ATCC 9144)0.1% ethanol0.94 mg/L[121]
MICS. aureus (ATCC 6538)Acetone4.00 mg/mLLimonene (93.20%)[99]

Commiphora guidotti (myrrh)MICS. aureus (ATCC 12600)Acetone1.50 mg/mL(E)-β-Ocimene (52.60%), α-santalene (11.10%), (E)-bisabolene (16.00%)[117]

Commiphora myrrha (myrrh)MICS. aureus (ATCC 12600)Acetone1.30 mg/mLFuranogermacrene (15.90%), furanoeudesma-1,3-diene (44.30%)[117]
S. aureus (ATCC 6538)2.00 mg/mLFuranoeudesma-1,3-diene (57.70%), lindestrene (16.30%)[117]

Coriandrum sativum (coriander), seedMICS. aureus (7 clinical isolates)0.5% DMSO with Tween 800.16 mg/mLNCR[122]

Cupressus arizonica (smooth cypress), branches MICS. aureus (ATCC 25923) 10% DMSO1.50 μg/mLα-Pinene (58.60%), δ-3-carene (15.60%) [123]
Cupressus arizonica (smooth cypress),female cones2.95 μg/mLα-Pinene (60.50%), δ-3-carene (15.30%)
Cupressus arizonica (smooth cypress), leaves0.98 μg/mLα-Pinene (20.00%), umbellulone (18.40%)

Cupressus sempervirens (cypress)MICS. aureus (ATCC 6538)Acetone12.00 mg/mLα-Pinene (41.20%), δ-3-carene (23.70%)[99]

Cymbopogon giganteus (lemongrass)MICS. aureus (ATCC 9144)0.5% ethanol2.10 mg/mLLimonene (42.00%), trans-p-mentha-1(7),8-dien-2-ol (14.20%), cis-p-mentha-1(7),8-dien-2-ol (12.00%)[124]

Cymbopogon citratus (lemongrass) MICS. aureus (ATCC 9144)0.5% ethanol2.50 mg/mLGeranial (48.10%), neral (34.60%), myrcene (11.00%)[124]
S. aureusDMSO≤1.00 μg/mLGeranial (47.34%), β-myrcene (16.53%), Z-citral (8.36%)[118]
MACS. aureus (MTCC 96)Sodium taurocholate0.80–0.27 μL/mLCitral (72.80%)[125, 126]
MICS. aureus (ATCC 6538)Acetone1.67 mg/mLGeranial (44.80%)[99]

Cymbopogon martinii (palmarosa)MACS. aureus (MTCC 96)Sodium taurocholate0.80 μL/mLGeraniol (61.6%)[125, 126]

Cymbopogon nardus (citronella)MICS. aureus (ATCC 6538)Acetone4.00 mg/mLCitronellal (38.30%), geraniol (20.70%), citronellol (18.80%)[99]

Daucus carota (carrot seed)MICS. aureus (ATCC 6538)Acetone2.00 mg/mLCarotol (44.40%)[99]

Eucalyptus camaldulensis (eucalyptus)MACS. aureus (ATCC 25923)Acetone3.90 μg/mL1,8-Cineol (54.37%), α-pinene (13.24%) [127]
S. aureus (clinical isolate)

Eucalyptus globulus (eucalyptus) MICS. aureus (ATCC 25923) Tween 80 10.00 mg/mL 1,8-Cineol (81.93%) [128]
MRSA (ATCC 10442)
MICS. aureus (ATCC 43387)DMSO0.20% v/vNCR[129]
MACS. aureus (MTCC 96)Sodium taurocholate0.41 μL/mLCineole (23.20%)[125, 126]
ADMMRSA (ATCC 33592) Tween 2085.60 μg/mLEucalyptol (47.20%), (+)-spathulenol (18.10%) [81]
S. aureus (ATCC 25922)51.36 μg/mL
MRSA (14 clinical isolates)8.56–85.60 μg/mL
MICS. aureus (ATCC 6538)Acetone4.00 mg/mL1,8-Cineole (58.00%), α-terpineol (13.20%)[99]
MICS. aureus (ATCC 25923)Acetone2.00 mg/mLNCR [130]
MRSA (ATCC 33592)0.75 mg/mL

Eucalyptus radiata (eucalyptus) MICS. aureus (ATCC 25923) Acetone2.00 mg/mL 1,8-Cineole , α-terpineol [130]
MRSA (ATCC 33592)1.00–2.00 mg/mL

Eucalyptus camaldulensis (eucalyptus)MICS. aureus (ATCC 25923)Acetone0.50 mg/mLNCR [130]
MRSA (ATCC 33592)

Eucalyptus citriodora (eucalyptus)MICS. aureus (ATCC 25923)Acetone1.00 mg/mLNCR [130]
MRSA (ATCC 33592)

Eucalyptus smithii (eucalyptus)MICS. aureus (ATCC 25923)Acetone2.00 mg/mLNCR [130]
MRSA (ATCC 33592)

Eucalyptus dives (eucalyptus)MICS. aureus (ATCC 25923)Acetone2.00 mg/mLNCR [130]
MRSA (ATCC 33592)1.00 mg/mL

Eucalyptus intertexta (eucalyptus)MICS. aureus (ATCC 29737)10% DSMO7.80 μg/mLNCR[131]

Eucalyptus largiflorens (eucalyptus)MACS. aureus (ATCC 25923)n.m.7.80 μg/mL1,8-Cineol (70.32%), α-pinene (15.46%) [127]
S. aureus (clinical isolate)
MICS. aureus (ATCC 29737)10% DSMO250.00 μg/mLNCR[131]

Eucalyptus melliodora (eucalyptus)MACS. aureus (ATCC 25923)n.m.3.90 μg/mL1,8-Cineol (67.65%), α-pinene (18.58%) [127]
S. aureus (clinical isolate)

Eucalyptus polycarpa (eucalyptus)MACS. aureus (ATCC 25923)n.m.1.95 μg/mL1,8-Cineol (50.12%) [127]
S. aureus (clinical isolate)3.90 μg/mL

Foeniculum dulce (fennel)MICS. aureus (ATCC 6538)Acetone2.00 mg/mLE-Anethole (79.10%)[99]

Foeniculum vulgare (fennel) MACS. aureus (ATCC 25923) DMSO10.00 mg/mLtrans-Anethole (68.53%), estragole (10.42%)[132]
Foeniculum vulgare (fennel) (6 samples) MICS. aureus1.00 μg/mLtrans-Anethole (33.3%), DL-limonene (19.66%), carvone (12.03%)[118]
S. aureus (ATCC 28213)125.00–500.00 μg/mLFenchone (16.90–34.70%), estragole (2.50–66.00%), trans-anethole (7.90–77.70%)[133]

Foeniculum vulgare Mill. ssp. vulgare (fennel), Aurelio MACS. aureus (ATCC 25923) Tween 2050.00–100.00 μg/mLLimonene (16.50–21.50%), (E)-anethole (59.80–66.00%) [134]
Foeniculum vulgare Mill. ssp. vulgare (fennel), SpartacoLimonene (0.20–17.70%), (E)-anethole (66.30–90.40%)

Geranium dissectum (geranium)MICS. aureusDMSO≤1.00 μg/mLβ-Citronellol (25.45%), geraniol (13.83%)[118]

Hyssopus officinalis (hyssop)MICS. aureus (ATCC 6538)Acetone3.00 mg/mLIsopinocamphone (48.70%), pinocamphone (15.50%)[99]

Juniperi aetheroleum (juniper)MAC80S. aureus (ATCC 6538)n.m.40.00% v/vα-Pinene (29.17%), β-pinene (17.84%), sabinene (13.55%) [135]
MAC80S. aureus (MFBF)15.00% v/v

Juniperus communis (juniper), berryMICS. aureus (ATCC 25923)n.m.10.00 mg/mLNCR[85]
MICMRSA (15 clinical isolates)Ethanol>2.00% v/v[136]

Juniperus excelsa (juniper), berries, DojranADMS. aureus (ATCC 29213)50% DSMO>50.00%α-Pinene (70.81%) [87]
Juniperus excelsa (juniper), leaves, Dojran125.00%α-Pinene (33.83%)
Juniperus excelsa (juniper), leaves, Ohrid125.00%Sabinene (29.49%)

Juniperus officinalis (juniper), berryMICS. aureus (ATCC 29213)Tween 8010.00 mg/mLα-Pinene (39.76%) [128]
Juniperus officinalis (juniper), berryMRSA (clinical isolates)20.00 mg/mL

Juniperus virginiana (juniper) MICS. aureus (ATCC 6538) Acetone2.00 mg/mLThujopsene (29.80%), cedrol (14.90%), α-cedrene (12.40%) [99]
Juniperus virginiana (juniper), berries3.00 mg/mLα-Pinene (20.50%), myrcene (13.70%), bicyclosesquiphellandrene (10.70%)

Kunzea ericoides (Kānuka)MACS. aureus (ATCC 6538)Tween 800.25% v/vα-Pinene (61.60%) [137]
MRSA (clinical isolate)0.20% v/v
MICS. aureus (ATCC 12600)Acetone8.00 mg/mLα-Pinene (26.2–46.7%), p-cymene (5.8–19.1%)[138]

Laurus nobilis (bay)MICS. aureus (ATCC 6538)Acetone0.83 mg/mLEugenol (57.20%), myrcene (14.30%), carvacrol (12.70%)[99]

Lavandula angustifolia (lavender) MICS. aureus (ATCC 6538)Acetone2.00 mg/mLLinalyl acetate (36.70%), linalool (31.40%), terpinen-4-ol (14.90%)[99]
S. aureus (NCTC 6571)10% DSMO310.00 μg/mLLinalool (25.10%), linalyl acetate (22.50%) [139]
S. aureus (NCTC 1803)320.40 μg/mL
MRSA (15 clinical isolates)Ethanol0.50% v/vNCR[136]
S. aureus (ATCC 12600)Acetone8.60 mg/mLLinalool (30.80%), linalyl acetate (31.30%)[140]
S. aureus (clinical strain and ATCC 6538) Acetone 2.00 mg/mL Linalyl acetate (36.7%), linalool (31.4%), terpinen-4-ol (14.9%) [99]
MRSA (clinical strain and 43300)
Methicillin-gentamicin-resistant S. aureus (MGRSA) (ATCC 33592)

Lavandula dentata (French lavender)MICS. aureus (BNI 18)5% DMSO1.53 mg/mLCamphor (12.40%)[141]
Lavandula officinalis (lavender)MICS. aureusDMSO≤1.00 μg/mLδ-3-Carene (17.14%), α-fenchene (16.79%), diethyl phthalate (13.84%)[118]
Lavandula stoechas (French lavender)MICS. aureus (STCC 976)Tween 802.00 μL/mL10s,11s-Himachala-3(12),4-diene (23.62%), cubenol (16.19%)[142]

Lavandula stoechas (French lavender), flowerMICMRSA (clinical isolate)20% DMSO31.25 μg/mLα-Fenchone (39.20%) [47]
Lavandula stoechas (French lavender), leaf125.00 μg/mLα-Fenchone (41.90%), 1,8-cineole (15.60%), camphor (12.10%)

Leptospermum scoparium (manuka)MACS. aureus (ATCC 6538)Tween 800.10% v/v(−)-()-Calamenene (14.50%), leptospermone (17.60%) [137]
MRSA (clinical isolate)0.05% v/v
MICS. aureus (ATCC 12600)Acetone4.00 mg/mLEudesma-4(14),11-diene (6.2–14.5%), α-selinene (5.90–13.5%), ()-methyl cinnamate (9.2–19.5%)[138]

Litsea cubeba (May Chang)MICS. aureus (ATCC 6538)Acetone1.50 mg/mLGeranial (45.60%), nerol (31.20%)[99]

Matricaria chamomilla (German chamomile)MICS. aureus (ATCC 6538)Acetone1.50 mg/mLBisabolene oxide A (46.90%), β-farnesene (19.20%)[99]

Matricaria recutita (German chamomile)ADM90S. aureus (ATCC 25923, 16 MRSA and 15 MSSA clinical isolates)Tween 8026.50 mg/mLChamazulene (31.48%), α-bisabolol (15.71%), bisabolol oxide (15.71%)[119]

Matricaria songarica (chamomile)MICS. aureus (CCTCC AB91093)Tween 8050.00 μg/mLE-β-Farnesene (10.58%), bisabolol oxide A (10.46%)[143]

Melaleuca alternifolia (tea tree)ADMS. aureus (NCIM 2079)Tween 801.00%NCR [79]
S. aureus (clinical isolate)
MACS. aureus (ATCC 6538) Tween 800.25% v/vα-Terpinene (11.40%), γ-terpinene (22.50%), terpinen-4-ol (35.20%) [137]
MRSA (clinical isolate)0.35% v/v
MICS. aureus (ATCC 29213)None used0.50% (v/v)Terpinen-4-ol (40.00%), δ-terpinen (13.00%), p-cymene (13.00%)[97]
MRSA (98 clinical isolates) n.m.512.00–2048.00 mg/L NCR[144]
S. aureus (NCIB 6571)1.00% v/v[145]
Coagulase-negative staphylococci (9 clinical isolates)Polyoxyl 35 castor oil0.63–2.50% v/vTerpinen-4-ol (>35.00%) [146]
MRSA (10 clinical isolates)0.30–0.63% v/v
0.30% v/v
MRSA (15 clinical isolates)Ethanol0.25% v/vNCR[136]
S. aureus (ATCC 12600)Acetone8.60 mg/mLTerpinen-4-ol (38.60%), γ-terpinene (21.60%)[140]
MIC90S. aureus (NCTC 6571) Tween 800.25% v/vTerpinen-4-ol (35.70%) [147]
S. aureus (105 clinical isolates)0.12–0.50% v/v
MICMRSA (60 clinical isolates, 29 mupirocin-resistant)0.25%[148]
MICS. aureus (NCTC 8325)n.m.0.50% (v/v)Terpinen-4-ol (39.80%), γ-terpinene (17.80%)[149]
0.25% (v/v)[150]
MIC90MRSA (100 clinical isolates)Tween 800.16–0.32%NCR[151]
MICS. aureus (69 clinical isolates)Tween 800.12–0.50% v/vTerpinen-4-ol (35.70%)[152]
ADMS. aureus (NCTC 4163)Tween 200.20% v/vTerpinen-4-ol (42.80%), γ-terpinene (18.20%) [115]
MRSA (clinical isolate)0.30% v/v
MICS. aureus (ATCC 6538)Acetone8.00 mg/mLTerpinen-4-ol (49.30%), -terpinene (16.90%)[99]
MACS. aureus (2 clinical isolates)n.m.0.10–0.20%Eucalyptol (70.08%) [153]
S. aureus (ATCC 25923)0.20%
S. aureus (NCTC 9518)0.63–1.25% v/vα-Pinene (11.95%), α-terpinene (14.63%), terpinen-4-ol (29.50%), p-cymene (17.74%) [154]
α-Pinene (24.87%), -terpinene (12.47%), terpinen-4-ol (28.59%)

Melaleuca cajuputi (cajuput) MICS. aureus (ATCC 25923) Tween 802.50 mg/mL 1,8-Cineol (67.60%) [128]
MRSA (ATCC 10442)5.00 mg/mL
MRSA (clinical isolate)2.50 mg/mL
MACS. aureus (ATCC 6538)0.20% v/v1,8-Cineole (55.50%) [137]
MRSA (clinical isolate)0.30% v/v

Melaleuca quinquenervia (niaouli)MACS. aureus (ATCC 6538)Tween 800.20% v/v1,8-Cineole (61.20%) [137]
MRSA (clinical isolate)0.30% v/v

Melaleuca viridiflora (niaouli)MICS. aureus (ATCC 6538)Acetone2.00 mg/mL1,8-Cineole (45.90%), -terpinene (21.00%)[99]

Melissa officinalis (lemon balm)MICS. aureus (NCTC 6571)10% DSMO300.60 μg/mL1,8-Cineol (27.40%), α-thujone (16.30%), β-thujone (11.20%), borneol (10.40%) [139]
MICS. aureus (NCTC 1803)330.30 μg/mL

Mentha piperita (peppermint) MICS. aureus (ATCC 12600)Acetone11.90 mg/mLMenthone (18.20%), menthol (42.90%) [140]
S. aureus (ATCC 25923) Tween 80 0.60 mg/mL 1,8-Cineol (12.06%), menthone (22.24%), menthol (47.29%) [128]
MRSA (ATCC 10442)
MRSA (clinical isolate)
S. aureus (ATCC 6538)DMSO0.63–2.50 mg/mLMenthol (27.50–42.30%), menthone (18.40–27.90%)[155]
S. aureus≤1.00 μg/mLMenthone (40.82%), carvone (24.16%)[118]
MRSA (15 clinical isolates)Ethanol0.50% v/vNCR[136]
S. aureus (ATCC 43387)DMSO0.20% v/v[129]
MACS. aureus (MTCC 96)Sodium taurocholate1.66 μL/mLMenthol (36.40%)[125, 126]
MICS. aureus (ATCC 9144)0.5% ethanol8.30 mg/mLMenthol (39.30%), menthone (25.20%)[156]
MICS. aureus (ATCC 6538)Acetone4.00 mg/mLMenthol (47.50%), menthone (18.60%)[99]

Myrtus communis (myrtle)MICS. aureus (ATCC 6538)Acetone2.00 mg/mLMyrtenyl acetate (28.20%), 1,8-cineole (25.60%), α-pinene (12.50%)[99]
ADMS. aureus (ATCC 6538)Tween 202.80 mg/mLNCR [157]
S. aureus (ATCC 29213)

Ocimum basilicum (basil)MICS. aureus (ATCC 9144)0.5% ethanol2.50 mg/mLLinalool (57.00%), eugenol (19.20%)[156]
MACS. aureus (ATCC 6538)n.m.1.25 μL/mLEugenol (62.60%), caryophyllene (21.51%)[62]
Tween 80% v/vLinalool (54.95%), methyl chavicol (11.98%)[158]
S. aureus (3 clinical strains)Tween 80 % v/vLinalool (54.95%), methyl chavicol (11.98%)[158]
MICS. aureus (ATCC 6538)Acetone1.50 mg/mLLinalool (54.10%)[99]
MIC90S. aureus (ATCC 6538)n.m.45.00 μg/mLMethyl chavicol (46.90%), geranial (19.10%), neral (15.15%)[159]
MICS. aureus (ATCC 6538)Tween 800.68–11.74 μg/mLLinalool (30.30–58.60%)[160]

Origanum acutidens (Turkey oregano) MICS. aureus (clinical isolate)10% DMSO125.00 μg/mLCarvacrol (72.00%) [161]
S. aureus (ATCC2913)

Origanum majorana (marjoram)MICS. aureus (ATCC 43387)DMSO0.05% v/vNCR[129]
S. aureus (ATCC 6538)Acetone2.00 mg/mL1,8-Cineole (46.00%), linalool (26.10%)[99]

Origanum microphyllum (oregano)MICS. aureus (ATCC 25923)Tween 806.21 mg/mLTerpin-4-ol (24.86%), γ-terpinene (13.83%), linalool (10.81%)[162]

Origanum scabrum (oregano)MICS. aureus (ATCC 25923)Tween 800.35 mg/mLcarvacrol (74.86%)[162]

Origanum vulgare (oregano)ADMS. aureus (ATCC 6538)1% DMSO0.13% v/vp-Cymene (14.60%), γ-terpinene (11.70%), thymol (24.70%), carvacrol (14.00%) [163]
S. aureus (ATCC 25923)
S. aureus (ATCC 43300)
MRSA (22 isolates)0.06–0.13% v/v
MICS. aureus (ATCC 6538)n.m.575.00 mg/LNCR[164]
MAC0.63.00 μL/mLCarvacrol (30.17%), p-cymene (15.20%), γ-terpinen (12.44%)[62]
MICS. aureus (ATCC 43387)DMSO0.10% v/vNCR[129]
ADMS. aureus (ATCC 6538)Tween 200.70 mg/mL [157]
S. aureus (ATCC 29213)

Origanum vulgare subsp. hirtum (Greek oregano)MICS. aureus (ATCC 25923)10% DMSO + Tween 80170.70 μg/mLLinalool (96.31%) [165]
Origanum vulgare subsp. vulgare (oregano)106.70 μg/mLThymol (58.31%), carvacrol (16.11%), p-cymene (13.45%)

Pelargonium graveolens (geranium) ADMS. aureus (ATCC 25923)10% DMSO>12.80 mg/mLNCR[80]
S. aureus (ATCC 6538)Tween 200.72 mg/mL [157]
S. aureus (ATCC 29213)
MICS. aureus (strains isolated from skin lesions) Ethanol0.25–1.50 mL/mL Citronellol (26.70%), geraniol (13.40%) [166]
S. aureus (strains isolated postoperatively)0.50–2.25 mL/mL
MRSA and MSSA (clinical strains)1.00 mL/mL
S. aureus (ATCC 6538)Acetone1.50 mg/mLCitronellol (34.20%), geraniol (15.70%)[99]

Perovskia abrotanoides (Russian sage)MICS. aureus (ATCC 25923)10% DMSO8.00 μL/mLCamphor (23.00%), 1,8-cineole (22.00%), α-pinene (12.00%)[167]

Pimpinella anisum (anise)MICS. aureusDMSO125.00 μg/mLNCR[168]
≤1.00 μg/mLAnethole (64.82%)[118]

Pinus sylvestris (pine)MICS. aureus (ATCC 6538)Acetone4.00 mg/mLBornyl acetate (42.30%), camphene (11.80%), α-pinene (11.00%)[99]

Piper nigrum (black pepper)MICS. aureus (ATCC 6538)Acetone2.00 mg/mLβ-Caryophyllene (33.80%), limonene (16.40%)[99]

Pogostemon cablin (patchouli)MICS. aureus (NCTC 6571)10% DSMO395.20 μg/mLα-Guaiene (13.80%), α-bulnesene (17.10%), patchouli alcohol (22.70%) [139]
S. aureus (NCTC 1803)520.00 μg/mL

Pogostemon patchouli (patchouli)MICS. aureus (ATCC 6538)Acetone1.50 mg/mLPatchouli alcohol (37.30%), α-bulnesene (14.60%), α-guaiene (12.50%)[99]

Rosmarinus officinalis (rosemary) MICS. aureus (ATCC 6538)Tween 800.13% v/v1,8-Cineole (27.23%), α-pinene (19.43%), camphor (14.26%), camphene (11.52%)[169]
S. aureus (NCTC 6571)10% DSMO305.30 μg/mL1,8-Cineol (29.2%), (+)-camphor (17.2%) [139]
S. aureus (NCTC 1803)310.40 μg/mL
MRSA (clinical isolate)Tween 800.03% v/v1,8-Cineole (26.54%), α-pinene (20.14%), camphene (11.38%), camphor (12.88%)[170]
S. aureus (MTCC 96)n.m.11.00 mg/mLNCR[171]
S. aureus (ATCC 6538)Hexane1.88–7.50 mg/mL1,8-Cineole (10.56–11.91%), camphor (16.57–16.89%), verbenone (17.43–23.79%)[172]
ADMS. aureus (ATCC 25923)10% DMSO12.80 mg/mLNCR[80]
S. aureus (ATCC 6538)Tween 20 5.60 mg/mL [157]
S. aureus (ATCC 29213)
MICS. aureus (ATCC 12600)Acetone6.20 mg/mL1,8-Cineole (41.40%), α-pinene (13.30%), camphor (12.40%)[140]
S. aureus (ATCC 43387)DMSO0.20% v/vNCR[129]
S. aureus (ATCC 6538)Acetone4.00 mg/mL1,8-Cineole (48.00%)[99]
ADM90S. aureus (ATCC 25923, 16 MRSA and 15 MSSA clinical isolates)Tween 808.60 mg/mLCamphor (27.51%), limonene (21.01%), myrcene (11.19%), α-pinene (10.37%)[119]

Salvia bracteata (sage)MICS. aureus (ATCC 25923)50.00 μg/mLCaryophyllene oxide (16.60%)[173]
Salvia eremophila (sage)MICS. aureus (ATCC 29737)10% DMSO8.00 μg/mLBorneol (21.83%), α-pinene (18.80%), bornyl acetate (18.68%)[174]
Salvia nilotica (sage)ADMS. aureus (ATCC 25923)n.m.5.40 mg/mLtrans-Caryophyllene (10.90%)[175]

Salvia officinalis (sage) MICS. aureus (NCTC 6571)10% DSMO302.40 μg/mL1,8-Cineol (27.40%), α-thujone (16.30%), β-thujone (11.20%), borneol (10.40%) [139]
S. aureus (NCTC 1803)324.30 μg/mL
S. aureus (ATCC 43387)DMSO0.20% v/vNCR[129]
ADMS. aureus (ATCC 6538)Tween 2011.20 mg/mLNCR [157]
S. aureus (ATCC 29213)5.60 mg/mL
S. aureus (ATCC 25923)n.m.7.50 mg/mL[176]

Salvia ringens (sage) MICS. aureus (ATCC 25923)n.m.NIα-Pinene (12.85%), 1,8-cineole (46.42%)[177]
Salvia rosifolia (sage) (3 samples)MRSA20% DMSO125.00–1000.00 μg/mLα-Pinene (15.70–34.80%), 1,8-cineole (16.60–25.10%), β-pinene (6.70–13.50%)[178]
Salvia rubifolia (sage)S. aureus (ATCC 25923)Tween 2050.00 μg/mLγ-Muurolene (11.80%)[173]

Salvia sclarea (clary sage)MICS. aureus (11 MRSA and 16 MSSA)Ethanol3.75–5.25Linalyl acetate (57.90%), linalool (12.40%)[179]
S. aureus (ATCC 6538)Acetone2.00 mg/mLLinalyl acetate (72.90%), linalool (11.90%)[99]

Santalum album (sandalwood)MICS. aureus (ATCC 6538)Acetone0.25 mg/mLα-Santalol (32.10%)[99]

Styrax benzoin (benzoin)MICS. aureus (ATCC 6538)Acetone2.00 mg/mLcinnamyl alcohol (44.80%), benzene propanol (21.70%)[99]

Syzygium aromaticum (clove) MICS. aureus (ATCC 6538)Tween 800.13% v/vEugenol (68.52%), β-caryophyllene (19.00%), 2-methoxy-4-[2-propenyl]phenol acetate (10.15%)[169]
S. aureusDMSO≤1.00 μg/mLEugenol (84.07%), isoeugenol (10.39%)[118]
ADMS. aureus (ATCC 25923)10% DMSO>6.40 mg/mLNCR[80]
MICS. aureus (ATCC 6538)Acetone1.50 mg/mLEugenol (82.20%), eugenol acetate (13.20%)[99]

Tagetes minuta (Mexican marigold)MIC90S. aureus (ATCC 6538)n.m.67.00 μg/mLDihydrotagetone (33.90%), E-ocimene (19.90%), tagetone (16.10%)[159]
Tagetes patula (French marigold)MICS. aureus (ATCC 6538)Acetone4.00 mg/mL(E)-β-Ocimene (41.30%), E-tagetone (11.20%), verbenone (10.90%)[99]

Thymbra spicata (thyme)MICS. aureus (ATCC 29213) Tween 802.25 mg/mLCarvacrol (60.39%), γ-terpinene (12.95%)[180]
Thymus capitatus (thyme)S. aureus (ATCC 25923)900.00 μg/mLp-Cymene (26.40%), thymol (29.30%), carvacrol (10.80%) [181]
Thymus capitatus (thyme), commercialα-Pinene (25.20%), linalool (10.30%), thymol (46.10%)
Thymus herba-barona (thyme), Gennargentu225.00 μg/mLThymol (46.90%), carvacrol (20.60%)
Thymus herba-barona (thyme), Limbara900.00 μg/mLp-Cymene (27.60%), thymol (50.30%)

Thymus hyemalis (thyme) (thymol, thymol/linalool, carvacrol chemotypes)MACS. aureus (CECT 239)95% ethanol<0.20–0.50 μL/mLp-Cymene (16.00–19.80%), linalool (2.10–16.60%), thymol (2.90–43.00%), carvacrol (0.30–40.10%)[61]

Thymus numidicusADMS. aureus (ATCC 25923)n.m.0.23 mg/mLNCR[176]
Thymus serpyllum (thyme)S. aureus (ATCC 6538)Tween 200.28 mg/mL [157]
S. aureus (ATCC 29213)0.70 mg/mL

Thymus vulgaris (thyme)MICS. aureusDMSO31.20 μg/mLNCR[168]
S. aureus (NCTC 6571)10% DSMO160.50 μg/mLp-Cymene (17.90%), thymol (52.40%) [139]
S. aureus (NCTC 1803)210.00 μg/mL
S. aureus (ATCC 25923)n.m.0.40 mg/mLNCR[85]
ADMS. aureus (ATCC 433000) Ethanol0.25 μL/mLThymol (38.1%), p-cymene (29.10%)[182]
S. aureus (2 multidrug-resistant clinical strains from hands)0.50 μL/mL Thymol (38.1%), p-cymene (29.10%) [182]
S. aureus (6 multidrug-resistant clinical strains from wounds)0.50–1.00 μL/mL
S. aureus (4 multidrug-resistant clinical strains from ulcers)0.50–0.75 μL/mL
S. aureus (multidrug-resistant clinical strain from abscesses)0.25 μL/mL
MICS. aureus (ATCC 12600)Acetone1.30 mg/mLThymol (47.20%), p-cymene (22.10%)[140]
MRSA (15 clinical isolates)Ethanol0.50% v/vNCR[136]
ADMMRSA (ATCC 33592)Tween 2018.50 μg/mLThymol (48.1%), p-cymene (15.60%), γ-terpinene (15.40%) [81]
S. aureus (ATCC 25922)
MRSA (14 clinical isolates)18.50–37.00 μg/mL
MICS. aureus (ATCC 6538)Acetone3.33 mg/mLp-Cymene (39.90%), thymol (20.70%)[99]

Thymus vulgaris (thyme) (thymol chemotype) MACS.aureus (CECT 239) 95% ethanol<0.20 μL/mLp-Cymene (18.70%), thymol (57.70%) [61]
Thymus zygis subsp. gracilis (thyme) (thymol and two linalool chemotypes)<0.20–1.20 μL/mLp-Cymene (0.50–11.20%), (E)-sabinene hydrate (0.20–18.20%), linalool (2.00–82.30%)

Vetiveria zizanioides/Andropogon muricatus (vetiver)MICS. aureus (ATCC 6538)Acetone0.75 mg/mLZizanol (13.6%), β-vetirenene (7.2%)[99]

name (common name), part of plant (if applicable).
: microdilution method; MAC: macrodilution method; ADM: agar dilution method; CTA: contact time assay.
Type Culture Collection, Rockville, USA (ATCC); Colección Espanõla de Cultivos Tipo (CECT); collection of microorganisms of the Department of Microbiology (MFBF); culture collection of antibiotics resistant microbes (CCRM); Eskişehir Osmangazi University, Faculty of Medicine, clinical isolate (OGU); Laboratorio de Microbiología, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina (LM); Microbial Type Culture Collection (MTCC); Mycology Laboratory (LM); National Center of Industrial Microorganisms (NCIM); National Collection of Type Cultures, London, Great Britain (NCTC); Spanish Collection of Type Cultures (STCC).
concentration was not included; n.m.: not mentioned.
: no inhibition.
: no composition results reported.

When considering the antimicrobial activity of the tested essential oils, it can be noted how the main compounds influence overall antimicrobial activity. Melaleuca alternifolia (tea tree), rich in terpinen-4-ol, showed noteworthy activity, and Anthemis aciphylla var. discoidea (chamomile) containing α-pinene and terpinen-4-ol displayed noteworthy activity (1.00 mg/mL) [114], whereas the essential oil predominantly containing terpinen-4-ol displayed an MIC value of 0.50 mg/mL. The Origanum spp. (Origanum scabrum and Origanum vulgare) were shown to display rather impressive antimicrobial activity, which appeared to predominantly be related to the amount of carvacrol [163]. Geraniol also appears to be a compound that influences antimicrobial activity against the staphylococci spp. as can be seen for Backhousia citriodora (lemon myrtle) and Cymbopogon martinii (palmarosa) (geraniol 61.6%) [125, 126]. Cymbopogon martinii, with lower levels of geranial (44.80%), showed moderate antimicrobial activity [99]. Mentha piperita (peppermint) had higher antimicrobial activity for oils with higher concentrations of menthol [128, 155]. Laurus nobilis (bay), Styrax benzoin, and Cinnamomum zeylanicum (cinnamon), each rich in eugenol, were found to have notable activity [99].

It is interesting to consider the essential oils investigated and to compare them to what is recommended in the aromatherapeutic literature. For example, Lavandula angustifolia (lavender) is recommended for abscesses, carbuncles, and wounds [2, 26, 32, 3643], which all involve S. aureus; however, in vitro activity was found to discount this oil as an antimicrobial [99, 136, 139, 140]. The same could be said about essential oils such as Achillea millefolium (yarrow) [112], Anthemis nobilis (Roman chamomile) [99], Boswellia carteri (frankincense) [116], Citrus aurantifolia (lime) [80], Foeniculum vulgare (fennel) [132, 133], and Melissa officinalis (lemon balm) [139].

Some clinical studies included the evaluation of the effects of essential oils on malodorous necrotic ulcers of cancer patients. The use of an essential oil combination (mostly containing Eucalyptus globulus (eucalyptus)) resulted in a decrease in inflammation, reduction of the odour, and improved healing rates [193]. Edwards-Jones et al. [194] performed a clinical study with a wound dressing containing essential oils to decrease infection risk. Ames [195] found Melaleuca alternifolia (tea tree) to be effective in treating wounds; and Matricaria recutita (German chamomile) with L. angustifolia at a 50 : 50 ratio diluted in calendula oil was found to improve leg ulcers and pressure sores.

Methicillin-resistant S. aureus hinders the rate of wound healing, which may lead to chronic wounds [196]. Delayed wound healing has been proven to lead to psychological stress and social isolation [197, 198]. A randomised controlled trial, consisting of 32 patients (16 in control group, 16 in placebo group) with stage II and above MRSA-colonised wounds that were not responding to treatment, was undertaken where the control group was treated with a 10% topical M. alternifolia preparation and was found to effectively decrease colonising MRSA in 87.5% of patients and result in a 100% healing rate within 28 days [196]. These studies lead to the high recommendation of the incorporation of this essential oil combination in palliative care.

Methicillin-resistant S. aureus may potentially be carried and propagated by hospital staff and patients, which is an acknowledged risk for hospital-acquired infections [147, 189]. Therefore, successful decolonisation of MRSA from patients and good hygiene may improve the microbial load, number of reinfections, and ultimately therapeutic outcomes of patients [199]. A topical preparation containing M. alternifolia essential oil has been considered for assistance in eradicating MRSA in hospitals, due to its reported efficacy [200]. The largest randomised trial against MRSA colonisation included 224 patients where the control group was treated with 2% nasal mupirocin applied three times a day, 4% chlorhexidine gluconate soap used at least once a day, and 1% silver sulfadiazine cream applied to skin infections once a day. The study group was treated with 10% M. alternifolia oil nasal cream applied three times a day and 5% M. alternifolia oil body wash used at least once daily with a 10% M. alternifolia cream applied to skin infections. The results showed that 41% of patients in the study group were cleared as opposed to 49% of patients on the standard therapy [200]. A small three-day pilot study was designed by Caelli et al. [189] to observe whether daily washing with a 5% M. alternifolia oil would clear MRSA colonisation which may result in ICU patient outcome improvement [199]. The test group made use of 4% M. alternifolia nasal ointment and 5% M. alternifolia oil body wash and was compared to a conventional treatment consisting of 2% mupirocin nasal ointment and triclosan body wash. The test group overall was found to have more improvement at the infection site when compared to the control group. Although the pilot study was too small to be statistically significant, the researchers did find that the M. alternifolia oil performed better than the conventional treatment and was effective, nontoxic, and well tolerated [189]. Messager et al. [90] tested 5% M. alternifolia ex vivo in a formulation, where it again was proven to decrease the pathogenic bacteria on the skin. In another study, M. alternifolia oil was investigated to determine the influence on healing rates [201]. The patients were treated with water-miscible tea tree oil (3.30%) solution applied as part of the wound cleansing regimen. This study used this oil as a wash only three times a week which is not how this oil is prescribed and hence the results were not positive. A more accurate method of study was shown by Chin and Cordell [202], where M. alternifolia oil was used in a dressing for wound healing abilities. All patients, except for one, were found to have an accelerated healing rate of abscessed wounds and cellulitis. The concluding evidence shows that there is definitely potential for the use of M. alternifolia (tea tree) oil as an additional/alternative treatment to standard wound treatments [203].

The healing potential of Commiphora guidotti (myrrh) was investigated via excisions of rats. The authors could confidently report on an increased rate in wound contraction and candid wound healing activity that was attributed to the antimicrobial and anti-inflammatory effects of this oil [204]. Ocimum gratissimum (basil) was also found by Orafidiya et al. [205] to promote wound healing by eradicating the infectious pathogens and by inducing early epithelialisation and moderate clotting formation, thereby accelerating scab formation, contraction, and granulation.

From these studies, clearly, M. alternifolia has shown great promise against S. aureus. However, considering the potential of essential oils in clinical practice and comparing them to essential oils with promising in vitro activity, other oils such as Cymbopogon citratus (lemongrass), Santalum album (sandalwood), and Vetiveria zizanioides/Andropogon muricatus (vetiver) should in the future be paid the same amount of attention.

4.1.2. Pathogens Involved in Acne

Pathogens associated with acne include Propionibacterium acnes, Propionibacterium granulosum, and Staphylococcus epidermidis [206208]. Methicillin-resistant S. epidermidis (MRSE) have become extensively problematic microorganisms in the recent years due to their antimicrobial resistance and P. acnes has developed resistance to tetracycline, erythromycin, and clindamycin. Both have also shown multidrug resistance, including against quinolones [158, 188, 206]. Table 4 displays the in vitro antimicrobial efficacies of commercial essential oils against bacteria involved in the pathogenesis of acne. When observing the number of commercial essential oils that are recommended for acne treatment, less than half of the commercial oils have actually focused on S. epidermidis, P. granulosum, and P. acnes. Overall, the acne pathogens have been sorely neglected in essential oil studies.

Essential Species Main Reference

Abies koreana (Korean fir) MICS. epidermidis (antibiotic-susceptible strain SK4) n.m.0.63 μL/mL Bornyl acetate (30.40%), limonene (19.00%) [208]
S. epidermidis (antibiotic-resistant strain SK9)0.31 μL/mL
S. epidermidis (antibiotic-resistant strain SK19)5.00 μL/mL
P. acnes (ATCC 3314)0.31 μL/mL
P. acnes (antibiotic-resistant strain SKA 4)
P. acnes (antibiotic-resistant strain SKA 7)0.63 μL/mL

Anthemis aciphylla var. discoidea (chamomile), flowers MICS. epidermidis (ATCC 12228) DMSO0.25 mg/mL-Pinene (39.00%), terpinen-4-ol (32.10%) [114]
Anthemis aciphylla var. discoidea (chamomile), aerial parts0.13 mg/mL-Pinene (49.40%), terpinen-4-ol (21.80%)
Anthemis aciphylla var. discoidea (chamomile), leaves0.06 mg/mLTerpinen-4-ol (24.30%)

Anthemis nobilis (chamomile)MICP. acnes (CMCC 65002)Tween 800.13% v/vNCR[209]

Cananga odorata var. fruticosa (dwarf ylang-ylang)
Cananga odorata (ylang-ylang)
ADMP. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 80>4.00% v/vNCR[210]

Cinnamomum burmannii (cinnamon stick) MICS. epidermidis (16 clinical isolates)5% propylene glycol (PG)0.50–2.00% Cinnamaldehyde [211]
S. epidermidis strains RP62A (ATCC 35984)1.00%
S. epidermidis (ATCC 12228)0.50%

Cinnamomum zeylanicum (cinnamon)MICP. acnes (CMCC 65002)Tween 800.012% v/vNCR[209]

Citrus aurantium (bitter orange), flowersMICS. epidermidis (ATCC 12228)50% DMSO1.25 mg/mLLimonene (27.50%), E-nerolidol (17.5%), -terpineol (14.00%)[120]

Citrus medica limonum (lemon)MICP. acnes (CMCC 65002)Tween 800.25% v/vNCR[209]

Citrus natsudaidai (Japanese summer orange)MICS. epidermidis (KCTC 3958)5% Tween 8010.00 μL/mLLimonene (81.60%) [102]
P. acnes (ATCC 6919)0.31 μL/mL

Citrus paradisi (grapefruit)MICP. acnes (CMCC 65002)Tween 800.25% v/vNCR[209]
MACS. epidermidis (KCTC 3958)>50.00 μL/mLLimonene (55.40–91.70%), myrcene (2.10–32.10%)[212]

Citrus species (citrus) (14 spp.) MACS. epidermidis (KCTC 3958) Tween 80>50.00 μL/mL Limonene (55.40–91.70%), myrcene (2.10–32.10%) [212]
P. acnes (ATCC 6919)1.25–>50.00 μL/mL

Coriandrum sativum (coriander)ADMP. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 801.00% v/vNCR [210]
Curcuma longa (turmeric)>4.00% v/v
Cymbopogon citratus (lemongrass)0.13% v/v
Cymbopogon nardus (citronella)

Eucalyptus globulus (eucalyptus) MICS. epidermidis (ATCC 14990)Tween 8010.00 mg/mL1,8-Cineol (81.93%)[128]
S. epidermidis (RP62A)5% DSMO4.00 mg/LNCR [213]
S. epidermidis (clinical isolate TK1)8.00 mg/L
P. acnes (DMST 14917)n.m.9.38 mg/mLp-Cymene (28.75%), -terpinene (44.60%)[214]
ADMP. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 804.00% v/vNCR[210]

Eucalyptus intertexta (eucalyptus)MICS. epidermidis (ATCC 12228)10% DSMO7.80 μg/mLNCR [131]
Eucalyptus largiflorens (eucalyptus)125.00 μg/mL

Foeniculum vulgare (fennel), Aurelio MACS. epidermidis (ATCC 12228) Tween 2050.00 μg/mLLimonene (16.50–21.50%), (E)-anethole (59.80–66.00%) [134]
Foeniculum vulgare (fennel), Spartaco25.00–50.00 μg/mLLimonene (0.20–17.70%), (E)-anethole (66.30–90.40%)
Foeniculum vulgare (fennel) (6 samples)MICDMSO250.00–750.00 μg/mLFenchone (16.90–34.70%), estragole (2.50–66.00%), trans-anethole (7.90–77.70%)[133]

Jasminum grandiflora (jasmine)MICP. acnes (CMCC 65002)Tween 800.50% v/v NCR[209]
Jasminum sambac (jasmine)ADMP. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 802.00% v/v[210]

Juniperi aetheroleum (juniper)MAC80S. epidermidis (MFBF)n.m.40.00% v/v-Pinene (29.17%), -pinene (17.84%), sabinene (13.55%)[135]
Juniperus communis (juniper)CTAP. acnes (ATCC 6919)PEG 2002.00 mg/mL-Pinene (22.75%), -myrcene (11.88%)[215]
Juniperus officinalis (juniper), berryMICS. epidermidis (ATCC 14990)Tween 8020.00 mg/mL-Pinene (39.76%)[128]

Kunzea ericoides (Kānuka)MACS. epidermidis (clinical isolate)Tween 800.25% v/v-Pinene (61.60%)[137]
MICS. epidermidis (ATCC 2223)Acetone8.00 mg/mL-Pinene (26.2–46.7%), p-cymene (5.8–19.1%) [138]
MICP. acnes (ATCC 11827)Acetone4.00 mg/mL

Lavandula angustifolia (lavender) MICS. epidermidis (ATCC 2223)Acetone6.20 mg/mLLinalool (30.80%), linalyl acetate (31.30%)[140]
S. epidermidis (antibiotic-susceptible strain SK4)n.m.1.00 μL/mL NCR [208]
S. epidermidis (antibiotic-resistant strain SK9)n.m.0.13 μL/mL
S. epidermidis (antibiotic-resistant strain SK19)n.m.1.00 μL/mL
P. acnes (ATCC 3314)n.m.0.25 μL/mL
P. acnes (antibiotic-resistant strain SKA 4)n.m.1.25 μL/mL
P. acnes (antibiotic-resistant strain SKA 7)n.m.0.25 μL/mL
ADMP. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 802.00% v/vNCR[210]

Lavandula stoechas (French lavender), flowerMICS. epidermidis (ATCC 12228)20% DMSO250.00 μg/mL-Fenchone (39.20%) [47]
Lavandula stoechas (French lavender), leafMIC-Fenchone (41.90%), 1,8-cineole (15.60%), camphor (12.10%)
Lavandula stoechas (lavender)MICP. acnes (CMCC 65002)Tween 800.13% v/vNCR[209]

Leptospermum scoparium (manuka)MACS. epidermidis (clinical isolate)Tween 800.05% v/v(−)-(E)-Calamenene (14.50%), leptospermone (17.60%)[137]
MICS. epidermidis (ATCC 2223)Acetone4.00 mg/mLEudesma-4(14),11-diene (6.20–14.50%), -selinene (5.90–13.50%), (E)-methyl cinnamate (9.20–19.50%) [138]
P. acnes (ATCC 11827)1.00 mg/mL

Melaleuca alternifolia (tea tree)ADMS. epidermidis (NCIM number 2493) Tween 801.00%NCR [79]
S. epidermidis (clinical isolate)
MACS. epidermidis (clinical isolate)0.45% v/v-Terpinene (11.40%), -terpinene (22.50%), terpinen-4-ol (35.20%)[137]
MICS. epidermidis (15 clinical isolates)0.12–1.00% v/vTerpinen-4-ol (35.70%)[152]
MICS. epidermidis (RP62A)5% DSMO2.00 mg/LNCR [213]
S. epidermidis (clinical isolate TK1)16.00 mg/L
MICS. epidermidis (ATCC 2223)Acetone6.20 mg/mLTerpinen-4-ol (38.60%), -terpinene (21.60%)[140]
MICS. epidermidis (antibiotic-susceptible strain SK4) n.m.0.13 μL/mLNCR [208]
S. epidermidis (antibiotic-resistant strain SK9)1.00 μL/mL
S. epidermidis (antibiotic-resistant strain SK19)
MACP. acnes (MTCC 1951)Tween 800.50% v/vNCR[79]
P. acnes (32 clinical strains)0.25–0.50%Terpinen-4-ol (35.70%)[92]
ADMP. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 801.00% v/vNCR[210]
MICP. acnes (ATCC 3314)n.m.0.25 μL/mLNCR [208]
P. acnes (antibiotic-resistant strain SKA 4)2.50 μL/mL
P. acnes (antibiotic-resistant strain SKA 7)0.25 μL/mL
MACS. epidermidis (NCTC 11047)n.m.0.63–1.25% v/v-Pinene (11.95%), -terpinene (14.63%), terpinen-4-ol (29.5%), p-cymene (17.74%) [154]
P. acnes (NCTC 737)0.31–0.63% v/v
S. epidermidis (NCTC 11047)0.63–1.25% v/v-Pinene (24.87%), -terpinene (12.47%), terpinen-4-ol (28.59%)
P. acnes (NCTC 737)0.31–0.63% v/v

Melaleuca cajuputi (cajuput)MACS. epidermidis (clinical isolate)Tween 800.40% v/v1,8-Cineole (55.50%)[137]
MICS. epidermidis (ATCC 14990)Tween 8010.00 mg/mL1,8-Cineol (67.60%)[128]

Melaleuca quinquenervia (niaouli)MACS. epidermidis (clinical isolate)tween 800.40% v/v1,8-Cineole (61.20%)[137]

Mentha piperita (peppermint) MICS. epidermidis (ATCC 14990)Tween 801.25 mg/mL1,8-Cineol (12.06%), menthone (22.24%), menthol (47.29%)[128]
S. epidermidis (NCTC 12228)DMSO0.63–2.50 mg/mLMenthol (27.50–42.30%), menthone (18.40–27.90%)[155]
S. epidermidis (ATCC 2223)Acetone6.20 mg/mLMenthone (18.20%), menthol (42.90%)[140]
S. epidermidis (antibiotic-susceptible strain SK4) n.m.0.13 μL/mL NCR [208]
S. epidermidis (antibiotic-resistant strain SK9)0.50 μL/mL
S. epidermidis (antibiotic-resistant strain SK19)
P. acnes (ATCC 3314)0.25 μL/mL
P. acnes (antibiotic-resistant strain SKA 4)0.63 μL/mL
P. acnes (antibiotic-resistant strain SKA 7)0.06 μL/mL

Mentha spicata (spearmint)MICP. acnes (CMCC 65002)Tween 800.25% v/vNCR[209]

Ocimum americanum (hoary basil)ADMP. acnes (DMST 14916)Polysorbate 80>5.00% v/vNeral (27.20%), geraniol (32.00%)[44]

Ocimum basilicum (basil)MACS. epidermidis (2 clinical strains)Tween 80(0.15–0.30) × 10−2% v/vLinalool (54.95%), methyl chavicol (11.98%)[158]
ADMP. acnes (DMST 14916)Polysorbate 802.00% v/vMethyl chavicol (93.00%)[44]
P. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 80>4.00% v/vNCR[210]

Ocimum sanctum (holy basil) ADMP. acnes (DMST 14916)Polysorbate 803.0% v/vEugenol (41.50%), methyl eugenol (11.80%), -caryophyllene (23.70%)[44]
Ocimum tenuiflorum (holy basil)P. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 802.00% v/vNCR[210]

Origanum acutidens (Turkey oregano)MICS. epidermis (A233)10% DMSO125.00 μg/mLCarvacrol (72.0%)[161]
Origanum microphyllum (oregano)S. epidermidis (ATCC 12228)Tween 805.32 mg/mLTerpin-4-ol (24.86%), -terpinene (13.83%), linalool (10.81%) [162]
Origanum scabrum (oregano)0.38 mg/mLCarvacrol (74.86%)

Origanum vulgare (oregano)ADMS. epidermidis (ATCC 12228) 1% DMSO0.13% v/vp-Cymene (14.60%), -terpinene (11.70%), thymol (24.70%), carvacrol (14.00%) [163]
ADMS. epidermidis (21 clinical isolates)0.06–0.13% v/v

Piper nigrum (black pepper)ADMP. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 80>4.00% v/vNCR[210]

Rosa centifolia (rose)MICP. acnes (CMCC 65002)Tween 800.03% v/vNCR[209]

Rosmarinus officinalis (rosemary) MICS. epidermidis (ATCC 12228)Tween 800.25% v/v1,8-Cineole (27.23%), -pinene (19.43%), camphor (14.26%), camphene (11.52%)[169]
S. epidermidis0.10% (v/v)1,8-Cineole (26.54%), -pinene (20.14%), camphene (11.38%), camphor (12.88%)[170]
S. epidermidis (MTCC 435)n.m.11.00 mg/mLNCR[171]
S. epidermidis (ATCC 2223)Acetone10.10 mg/mL1,8-Cineole (41.40%), -pinene (13.30%), camphor (12.40%)[140]

Salvia bracteata (sage)MACS. epidermidis (ATCC 12228)Tween 2050.00 μg/mLCaryophyllene oxide (16.6%)[173]

Salvia eremophila (sage)MICS. epidermidis (ATCC 12228)10% DMSO32.00 μg/mLBorneol (21.83%), -pinene (18.80%), bornyl acetate (18.68%)[174]

Salvia nilotica (sage)ADMS. epidermidis (ATCC 12228)n.m.5.50 mg/mLtrans-Caryophyllene (10.90%)[175]

Salvia ringens (sage)MICS. epidermidis (ATCC 12228)n.m.NI-Pinene (12.85%), 1,8-cineole (46.42%)[177]

Salvia rosifolia (sage) (3 samples)MICS. epidermidis (ATCC 12228)20% DMSO125.00–1000.00 μg/mL-Pinene (15.70–34.80%), 1,8-cineole (16.60–25.10%), -pinene (6.70–13.50%)[178]

Salvia rubifolia (sage)MACS. epidermidis (ATCC 12228)Tween 2050.00 μg/mL-Muurolene (11.80%)[173]

Salvia sclarea (clary sage)MICS. epidermidis (19 clinical isolates)Ethanol4.50–6.25Linalyl acetate (57.90%), linalool (12.40%)[179]

Syzygium aromaticum (clove)MICS. epidermidis (ATCC 12228)Tween 80 0.25% v/vEugenol (68.52%), -caryophyllene (19.00%), 2-methoxy-4-[2-propenyl]phenol acetate (10.15%)[169]
ADMP. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 80NCR[210]
MICP. acnesn.m.0.31 mg/mLDL-Limonene (61.60%)[216]

Thymus capitatus (thyme)MICS. epidermidis (ATCC 12228)Tween 80900.00 μg/mLp-Cymene (26.40%), thymol (29.30%), carvacrol (10.80%) [181]
Thymus capitatus (thyme), commercial-Pinene (25.20%), linalool (10.30%), thymol (46.10%)
Thymus herba-barona (thyme), Gennargentu450.00 μg/mLThymol (46.90%), carvacrol (20.6 0%)
Thymus herba-barona (thyme), Limbara900.00 μg/mLp-Cymene (27.60%), thymol (50.30%)

Thymus quinquecostatus (thyme), JejuMACP. acnes (ATCC 6919)n.m.0.50 mg/mLp-Cymen-3-ol (50.41%), p-cymen-2-ol (24.06%), cymene (19.04%) [207]
P. granulosum (ATCC 25564)

Thymus vulgaris (thyme)MICS. epidermidis (ATCC 2223)Acetone4.70 mg/mLThymol (47.20%), p-cymene (22.10%)[140]
P. acnes (CMCC 65002)Tween 800.02% v/vNCR[209]

Zingiber officinale (ginger)MICP. acnes (CMCC 65002)Tween 800.25% v/vNCR[209]

Zingiber officinale Roscoe (ginger)ADMP. acnes (DMST 4916, 14917, 4918, 21823, 21823, 21824)0.5% polysorbate 80>4.00% v/vNCR[210]

name (common name), part of plant (if applicable).
: microdilution method; MAC: macrodilution method; ADM: agar dilution method; CTA: contact time assay.
Type Culture Collection, Rockville, USA (ATCC); Colección Espanõla de Cultivos Tipo (CECT); collection of microorganisms of the Department of Microbiology (MFBF); culture collection of antibiotics-resistant microbes (CCRM); Eskişehir Osmangazi University, Faculty of Medicine, clinical isolate (OGU); Laboratorio de Microbiología, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina (LM); Microbial Type Culture Collection (MTCC); Mycology Laboratory (LM); National Center of Industrial Microorganisms (NCIM); National Collection of Type Cultures, London, Great Britain (NCTC); Spanish Collection of Type Cultures (STCC).
concentration was not included; n.m.: not mentioned.
: no inhibition.
: no composition results reported.

For Anthemis aciphylla var. discoidea (chamomile) 0.13–0.25 mg/mL, initially, it appeared that higher α-pinene and lower terpinen-4-ol showed higher antimicrobial activity. However, the sample with terpinen-4-ol predominantly as its main component displayed the best activity at 0.06 mg/mL. This makes α-pinene appear as an antimicrobial antagonist. Cinnamomum zeylanicum, Rosa centifolia (rose), L. angustifolia, and Syzygium aromaticum (clove) displayed noteworthy antimicrobial activity against both S. epidermidis and P. acnes. Only the latter two are, however, recommended in the aromatherapeutic literature for the treatment of acne. Leptospermum scoparium (manuka) showed noteworthy activity for both P. acnes and S. epidermidis; however, Tween 80 was used as a solvent, which may overexaggerate the antimicrobial activity. Another study also found L. scoparium to effectively inhibit P. acnes. As was seen against S. aureus, O. scabrum and O. vulgare also notably inhibited S. epidermidis. Unfortunately, these oils were not studied against P. acnes. Cymbopogon citratus was shown to effectively inhibit P. acnes; however, no data was available against S. epidermidis. Essential oils such as S. album, V. zizanioides, Viola odorata (violet), Citrus aurantium var. amara (petitgrain), and Citrus bergamia (bergamot) are a few that are recommended for the treatment of acne and other microbial infections [2, 26, 32, 36, 37, 4043] in the aromatherapeutic literature that are yet to be investigated.

Some clinical studies have shown promising results. A four-week trial comparing O. gratissimum oil with 10% benzoyl peroxide and a placebo was conducted and was aimed at reducing acne lesions in students. The 2% and 5% O. gratissimum oils in the hydrophilic cetomacrogol base were found to reduce acne lesions faster than standard therapy, and they were well tolerated. The 5% preparation, despite being highly effective, caused skin irritation. Overall, O. gratissimum oil showed excellent potential in the management of acne as it was as effective as benzoyl peroxide, although it was less popular with patients due to the unpleasant odour [217].

Melaleuca alternifolia oil demonstrated in vitro antimicrobial and anti-inflammatory activity against P. acnes and S. epidermidis and is in fact the essential oil on which most clinical trials have been undertaken. Bassett et al. [218] performed one of the first rigorous single-blinded randomised (RCT) controlled trials consisting of 124 patients that assessed the efficacy of 5% M. alternifolia gel in comparison to 5% benzoyl peroxide lotion in the management of mild to moderate acne. Both treatments showed equal improvement in the acne lesions. Enshaieh et al. [219] evaluated the efficacy of 5% M. alternifolia on mild to moderate acne vulgaris. The 5% M. alternifolia oil was found to be effective in improving the number of papules in both inflammatory and noninflammatory acne lesions and was found to be more effective than the placebo. Proven efficacy has made M. alternifolia preparations popular in acne products.

Other oil studies included a gel formulation containing acetic acid, Citrus sinensis (orange), and Ocimum basilicum (sweet basil) essential oils, which was tested in acne patients. The combination of these antimicrobial essential oils and the keratolytic agent resulted in a 75% improvement in the rate of acne lesion healing [220].

If one examines the results displayed in Table 4, essential oils such as Anthemis aciphylla var. discoidea (chamomile), C. zeylanicum, Citrus aurantium (bitter orange), O. vulgare (oregano), and S. aromaticum displayed higher antimicrobial activity in vitro than M. alternifolia, yet these essential oils have to be investigated clinically.

4.1.3. Gram-Negative Bacteria

The Gram-negative bacterial cell wall consists of a 2-3 nm thick peptidoglycan layer (thinner than Gram-positive bacteria), which means that the cell wall consists of a very small percentage of the bacteria. The cell wall is further surrounded by an outer membrane (OM) which is comprised of a double layer of phospholipids that are linked to an inner membrane by lipopolysaccharides (LPS). This OM protects the bacteria from lipophilic particles; however, it makes them more vulnerable to hydrophilic solutes due to the abundance of porin proteins that serve as hydrophilic transmembrane channels [184, 221, 222].

Gram-negative pathogens present a serious threat with regard to drug resistance, especially Escherichia coli and Pseudomonas aeruginosa [190, 192]. These pathogens that are found to colonise wounds often cause multidrug resistance [166, 223]. β-Lactamase-positive E. coli is appearing frequently among nonhospital patients [224]. Pseudomonas aeruginosa is a regular cause of opportunistic nosocomial infections [187]. It is often involved in localised skin infections, green nail syndrome, and interdigital infection, colonises burn wounds, and may expand into a life-threatening systemic illness [225].

A number of essential oils display antimicrobial activity against E. coli and P. aeruginosa with the predominant studies having been done against E. coli (Table 5). The Gram-negative pathogens appear to be a lot more resistant to essential oil inhibition than the Gram-positive bacteria, but this a known fact.

Essential Species Main Reference

Abies balsamea (fir)MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mL-Pinene (31.00%), bornyl acetate (14.90%), -3-carene (14.20%)[99]

Abies holophylla (Manchurian fir)MICE. coli (ATCC 10536)DMSO21.8 mg/mLBicyclo[2.2.1]heptan-2-ol (28.05%), -3-carene (13.85%), -pinene (11.68%), camphene (10.41%) [111]
E. coli (ATCC 25922)
E. coli (ATCC 33312)
P. aeruginosa (NCTC 10490)21.80 mg/mL

Abies koreana (Korean fir)MICE. coli (ATCC 10536)DMSO21.8 mg/mLBornyl ester (41.79%), camphene (15.31%), -pinene (11.19%) [111]
E. coli (ATCC 25922)
E. coli (ATCC 33312)10.9 mg/mL
P. aeruginosa (NCTC 10490)21.80 mg/mL

Achillea millefolium (yarrow)MICP. aeruginosa (ATCC 27853)Tween 80NIEucalyptol (24.60%), camphor (16.70%), -terpineol (10.20%) [112]
E. coli (ATCC 25922)
Achillea setacea (bristly yarrow)E. coli (ATCC 25922)0.5% Tween 8072.00 mg/mLSabinene (10.80%), eucalyptol (18.50%) [113]
P. aeruginosa (ATCC 27853)72.00 mg/mL
Achillea teretifolia (bristly yarrow)E. coli (ATCC 25922)36.00 mg/mLEucalyptol (19.90%), camphor (11.10%), borneol (11.90%)
P. aeruginosa (ATCC 27853)72.00 mg/mL

Angelica archangelica (angelica) rootMICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mL-Phellandrene (18.50%), -pinene (13.70%), -phellandrene (12.60%), -3-carene (12.10%) [99]
Angelica archangelica (angelica) seed-Phellandrene (59.20%)

Aniba rosaeodora (rosewood)MICE. coli (ATCC 25922)n.m.0.40 mg/mLNCR[85]

Anthemis aciphylla var. discoidea (chamomile), flowersMICE. coli (ATCC 25922)DMSO1.00 mg/mL-Pinene (39.00%), terpinen-4-ol (32.10%) [114]
P. aeruginosa (ATCC 27853)0.25 mg/mL

Anthemis aciphylla var. discoidea (chamomile), aerial partsMICE. coli (ATCC 25922)DMSO1.00 mg/mL-Pinene (49.40%), terpinen-4-ol (21.80%) [114]
P. aeruginosa (ATCC 27853)

Anthemis aciphylla var. discoidea (chamomile), leavesMICE. coli (ATCC 25922)DMSO0.50 mg/mLTerpinen-4-ol (24.30%) [114]
P. aeruginosa (ATCC 27853)

Anthemis nobilis (chamomile)MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mL2-Methylbutyl-2-methyl propanoic acid (31.50%), limonene (18.30%), 3-methylpentyl-2-butenoic acid (16.70%), isobutyl isobutyrate (10.00%)[99]

Artemisia dracunculus (tarragon) MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mLEstragole (82.60%)[99]

Backhousia citriodora (lemon myrtle)ADME. coli (NCTC 8196)Tween 800.03% v/vGeranial (51.40%), neral (40.90%) [115]
P. aeruginosa (NCTC 6750)2.00% v/v

Boswellia carteri (frankincense) (9 samples)MICE. coli (ATCC 25922) Acetone4.00–12.00 mg/mL-Pinene (4.80–40.40%), myrcene (1.60–52.40%), limonene (1.90–20.40%), -thujene (0.30–52.40%), -cymene (2.70–16.90%), -pinene (0.30–13.10%) [116]
Boswellia frereana (frankincense) (3 samples)4.00–6.00 mg/mL-Pinene (2.00–64.70%), -thujene (0.00–33.10%), -cymene (5.40–16.90%)
Boswellia neglecta (frankincense)E. coli (ATCC 8739)Acetone3.00 mg/mLNCR[117]
E. coli (ATCC 25922)6.00 mg/mL-Pinene (43.40%), -pinene (13.10%)[116]
P. aeruginosa (ATCC 27858)1.30 mg/mLNCR [117]
Boswellia papyrifera (frankincense)E. coli (ATCC 8739)3.30 mg/mL
P. aeruginosa (ATCC 27858)1.50 mg/mL
Boswellia rivae (frankincense)E. coli (ATCC 8739)3.00 mg/mL
P. aeruginosa (ATCC 27858)1.00 mg/mL
Boswellia sacra (frankincense) (2 samples)E. coli (ATCC 25922)4.00–6.00 mg/mL-Pinene (18.30–28.00%), -thujene (3.90–11.20%), limonene (11.20–13.10%) [116]
Boswellia spp. (frankincense) (4 samples)6.00 mg/mL-Pinene (18.80–24.20%), limonene (11.70–19.00%)
Boswellia thurifera (frankincense)-Pinene (28.00%), limonene (14.60%)

Cananga odorata (ylang-ylang)MICP. aeruginosa (ATCC 27858)Acetone3.00 mg/mLBicyclosesquiphellandrene (19.50%), -farnesene (13.90%) [99]
Cananga odorata (ylang-ylang), heads1.50 mg/mLBenzyl acetate (31.90%), linalool (27.00%), methyl benzoate (10.40%)

Canarium luzonicum (elemi)MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mLLimonene (41.90%), elemol (21.60%), -phellandrene (11.40%)[99]

Carum carvi (caraway) MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mLLimonene (27.60%), carvone (67.50%)[99]
P. aeruginosaDMSO16.00 μg/mLDL-Limonene (53.35%), -selinene (11.08%), -elemene (10.09%)[118]

Caryophyllus aromaticus (clove)ADM90P. aeruginosa (ATCC 27853 and 15 clinical isolates)Tween 803.00 mg/mLEugenol (75.85%), eugenyl acetate (16.38%) [119]
E. coli (ATCC 25922 and 15 clinical isolates)

Cinnamomum cassia (cinnamon)MICP. aeruginosaDMSO≤1.00 μg/mLtrans-Caryophyllene (17.18%), eugenol (14.67%), linalool L (14.52%), trans-cinnamyl acetate, (13.85%), cymol (11.79%), cinnamaldehyde (11.25%)[118]

Cinnamomum zeylanicum (cinnamon)MACE. coli (ATCC 25922)75% ethanol200.00 mg/LNCR [231]
E. coli (10 clinical strains)400.00 mg/L
ADME. coliDMSO1.25 μL/mLNCR[232]
E. coli (ATCC 25922)10% DMSO1.6 mg/mLCinnamaldehyde (52.42%)[80]
MICP. aeruginosa (ATCC 27853)75% ethanol400.00 mg/LNCR [231]
P. aeruginosa (clinical strain)
ADMP. aeruginosa (ATCC 27853)10% DMSO0.80 mg/mLCinnamaldehyde (52.42%)[80]
MICAcetone1.50 mg/mLEugenol (80.00%)[99]
ADM90P. aeruginosa (ATCC 27853 and 15 clinical isolates)Tween 800.80 mg/mLCinnamaldehyde (86.31%) [119]
E. coli (ATCC 25922 and 15 clinical isolates)0.25 mg/mL

Citrus aurantifolia (lime)ADME. coli (ATCC 25922)10% DMSO6.40 mg/mLNCR [80]
P. aeruginosa (ATCC 27853)

Citrus aurantium (bitter orange), flowersMICE. coli (ATCC 25922)10% DMSO1.25 mg/mLLimonene (27.50%), -terpineol (14.00%), -nerolidol (17.50%), -terpinyl acetate (11.7%) [120]
E. coli (ATCC 8739)
P. aeruginosa (ATCC 9027)2.50 mg/mL

Citrus aurantium (petitgrain)MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mLLinalyl acetate (54.90%), linalool (21.10%)[99]

Citrus bergamia (bergamot)MACE. coli (ATCC 8739)n.m.5.0 μL/mLBergamol (16.10%), linalool (14.02%), D-limonene (13.76%)[62]

Citrus grandis (grapefruit)MICP. aeruginosa (ATCC 27858)Acetone1.50 mg/mLLimonene (74.80%)[99]
ADME. coliDMSO2.5 μL/mLNCR[232]

Citrus medica limonum (lemon) ADME. coli (ATCC 25922)10% DMSO6.4 mg/mLNCR [80]
P. aeruginosa (ATCC 27853)12.80 mg/mL
MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mL[99]

Citrus sinensis (orange)ADME. coli (ATCC 25922)10% DMSO12.8 mg/mLNCR[80]
MACE. coli (ATCC 10536)0.1% ethanol1.875 mg/L[121]
ADMP. aeruginosa (ATCC 27853)10% DMSO12.80 mg/mL[80]
MACP. aeruginosa (ATCC 15442)0.1% ethanol1.88 mg/mL[121]
MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mLLimonene (93.20%)[99]

Commiphora guidotti (myrrh) MICE. coli (ATCC 8739)Acetone4.00 mg/mL( )--Ocimene (52.60%), -santalene (11.10%), ()--bisabolene (16.00%) [117]
P. aeruginosa (ATCC 27858)1.40 mg/mL
Commiphora myrrha (myrrh)E. coli (ATCC 8739)1.00 mg/mLFuranogermacrene (15.9%), furanoeudesma-1,3-diene (44.3%)
P. aeruginosa (ATCC 27858)0.50 mg/mL
P. aeruginosa (ATCC 27858)4.00 mg/mLFuranoeudesma-1,3-diene (57.70%), lindestrene (16.30%)[99]

Coriandrum sativum (coriander), seedMICE. coli (7 clinical isolates)0.5% DMSO with Tween 800.14 mg/mLNCR [122]
Cumin cymene (cumin) (6 samples)0.30 mg/mL

Cupressus arizonica (smooth cypress)MICP. aeruginosa (ATCC 27853)10% DMSO6.02–23.60 μg/mL-Pinene (20.00–60.50%), -3-carene (1.00–15.60%), umbellulone (0.80–18.40%) [123]
Cupressus arizonica (smooth cypress), branchesE. coli (ATCC 25922)0.37 μg/mL-Pinene (58.60%), -3-carene (15.60%)
P. aeruginosa (ATCC 27853)11.80 μg/mL
Cupressus arizonica (smooth cypress), female conesE. coli (ATCC 25922)2.95 μg/mL-Pinene (60.50%), -3-carene (15.30%)
P. aeruginosa (ATCC 27853)6.02 μg/mL
Cupressus arizonica (smooth cypress), leavesE. coli (ATCC 25922)0.38 μg/mL-Pinene (20.00%), umbellulone (18.40%)
P. aeruginosa (ATCC 27853)23.60 μg/mL
Cupressus sempervirens (cypress)P. aeruginosa (ATCC 27853)Acetone2.00 mg/mL-Pinene (41.20%), -3-carene (23.70%)[99]

Cymbopogon giganteus (lemongrass) MICE. coli (CIP 105182)0.5% ethanol6.3 mg/mLLimonene (42.00%), trans--mentha-1(7),8-dien-2-ol (14.20%), cis--mentha-1(7),8-dien-2-ol (12.00%) [124]
P. aeruginosa (CRBIP 19.249)70.00 mg/mL

Cymbopogon citratus (lemongrass)MICE. coli (CIP 105182)0.5% ethanol10 mg/mLGeranial (48.1%), neral (34.6%), myrcene (11.0%)[124]
MACE. coli (clinical isolate VR 12 and MTCC 424)Sodium taurocholate1.66–3.33 μL/mLCitral (72.80%)[125, 126]
P. aeruginosa (MTCC 424 and clinical isolate VR 6)11.60–20.00 μL/mL
MICP. aeruginosa (CRBIP 19.249)0.5% ethanol80.00 mg/mLGeranial (48.10%), neral (34.60%), myrcene (11.00%)[124]
P. aeruginosa (ATCC 27858)Acetone1.50 mg/mLGeranial (44.80%)[99]
P. aeruginosaDMSO16.00 μg/mLGeranial (47.34%), -myrcene (16.53%), Z-citral (8.36%)[118]

Cymbopogon martinii (palmarosa)MACE. coli (clinical isolate VR 12 and MTCC 424)sodium taurocholate1.66–4.16 μL/mLGeraniol (61.60%)[125, 126]
P. aeruginosa (MTCC 424 and clinical isolate VR 6)8.33–20.00 μL/mL

Cymbopogon nardus (citronella)MICP. aeruginosa (ATCC 27858)acetone1.50 mg/mLCitronellal (38.30%), geraniol (20.70%), citronellol (18.80%) [99]
Daucus carota (carrot seed)3.00 mg/mLCarotol (44.40%)

Eucalyptus camaldulensis (eucalyptus) ADME. coliDMSO5.00 μL/mLNCR[232]
MICE. coli (ATCC 25922)Acetone2.00 mg/mL [130]
P. aeruginosa (ATCC 27853)1.00 mg/mL

Eucalyptus globulus (eucalyptus)ADME. coli (ATCC3428)Tween 2051.36 μg/mLEucalyptol (47.20%), (+)-spathulenol (18.10%)[81]
MICE. coli (ATCC 25922)Tween 8010.00 mg/mL 1,8-Cineol (81.93%)[128]
P. aeruginosa (ATCC 27853)10.00 mg/mL[128]
MACE. coli (clinical isolate and MTCC 424)Sodium taurocholate1.66–3.33 μL/mLCineole (23.20%) [125, 126]
P. aeruginosa (MTCC 424 and clinical isolate VR 6)8.33–20.00 μL/mL
MICP. aeruginosa (ATCC 9027)DMSO0.10% v/vNCR[129]
P. aeruginosa (ATCC 27858)Acetone3.00 mg/mL1,8-Cineole (58.00%), -terpineol (13.20%)[99]
E. coli (ATCC 25922)2.00 mg/mLNCR [130]
P. aeruginosa (ATCC 27853)1.00 mg/mL
Eucalyptus radiata (eucalyptus)E. coli (ATCC 25922)Acetone2.00 mg/mL1,8-Cineole (), -terpineol ()[130]
P. aeruginosa (ATCC 27853)1.00 mg/mL[130]
Eucalyptus citriodora (eucalyptus)E. coli (ATCC 25922)2.00 mg/mLNCR[130]
P. aeruginosa (ATCC 27853)1.00 mg/mL[130]
Eucalyptus smithii (eucalyptus)E. coli (ATCC 25922)2.00 mg/mLNCR[130]
P. aeruginosa (ATCC 27853)2.00 mg/mL[130]
Eucalyptus dives (eucalyptus)E. coli (ATCC 25922)2.00 mg/mLNCR[130]
P. aeruginosa (ATCC 27853)1.00 mg/mL[130]
Eucalyptus intertexta (eucalyptus)E.coli (ATCC 10536)10% DSMO15.6 μg/mLNCR [131]
P. aeruginosa (ATCC 27853)NI
Eucalyptus largiflorens (eucalyptus)E.coli (ATCC 10536)
P. aeruginosa (ATCC 27853)

Foeniculum dulce (fennel)MICP. aeruginosa (ATCC 27858)Acetone3.00 mg/mL-Anethole (79.10%)[99]

Foeniculum vulgare (fennel) MACE. coli (ATCC 25922)DMSO0.25 mg/mLtrans-Anethole (68.53%), estragole (10.42%) [132]
P. aeruginosa (ATCC 9027)10.00 mg/mL
MICP. aeruginosa16.00 μg/mLtrans-Anethole (33.3%), DL-limonene (19.66%), carvone (12.03%)[118]
Foeniculum vulgare (fennel) (6 samples)MICP. aeruginosa (ATCC 27853)1000.00–2000.00 μg/mLFenchone (16.90–34.70%), estragole (2.50–66.00%), trans-anethole (7.90–77.70%) [133]
E. coli (ATCC 25922)62.50–500 μg/mL

Foeniculum vulgare Mill. ssp. vulgare (fennel), Aurelio MACP. aeruginosa (ATCC 27853)Tween 20100.00 μg/mLLimonene (16.50–21.50%), ()-anethole (59.80–66.00%) [134]
E. coli (ATCC 25922)50.00 μg/mL
Foeniculum vulgare Mill. ssp. vulgare (fennel), SpartacoE. coli (ATCC 25922)50.00–100.00 μg/mLLimonene (0.20–17.70%), ()-anethole (66.30–90.40%)
P. aeruginosa (ATCC 27853)≥100.00 μg/mL

Geranium dissectum (geranium)MACP. aeruginosaDMSO16.00 μg/mL-Citronellol (25.45%), geraniol (13.83%)[118]

Hyssopus officinalis (hyssop)MACP. aeruginosa (ATCC 27858)Acetone2.00 mg/mLIsopinocamphone (48.70%), pinocamphone (15.50%)[99]

Jasminum sambac (jasmine)MACE. coli (MTCC 443)Sodium taurocholate31.25 μL/mLLinalool (59.00%), benzyl acetate (22.50%)[233]

Juniperus excelsa (juniper), berries, OhridADME. coli (25927)50% DSMO50.00%Sabinene (58.85%)[87]
Juniperus officinalis (juniper), berryMICE. coli (ATCC 25922)Tween 8020.00 mg/mL-Pinene (39.760%) [128]
P. aeruginosa (ATCC 27853)
Juniperus virginiana (juniper)P. aeruginosa (ATCC 27858)Acetone2.00 mg/mLThujopsene (29.80%), cedrol (14.90%), -cedrene (12.40%) [99]
Juniperus virginiana (juniper), berries-Pinene (20.50%), myrcene (13.70%), bicyclosesquiphellandrene (10.70%)

Kunzea ericoides (Kānuka) MACE. coli (ATCC 11229)Tween 802.00% v/v-pinene (61.60%) [137]
P. aeruginosa (ATCC 15442)2.00% v/v
MICP. aeruginosa (ATCC 9027)Acetone4.00 mg/mL-Pinene (26.20–46.70%), p-cymene (5.80–19.10%)[138]

Laurus nobilis (bay)MICP. aeruginosa (ATCC 27858)Acetone2.67 mg/mLEugenol (57.20%), myrcene (14.30%), chavicol (12.70%)[99]

Lavandula angustifolia (lavender)MICE. coli (ATCC 8739)10% DSMO730.1 μg/mLLinalool (25.10%), linalyl acetate (22.50%) [139]
E. coli (ampicillin-resistant NCTC 10418)722.2 μg/mL
P. aeruginosa (NCTC 1662)1040.00 μg/mL
E. coli (ATCC 11775)Acetone6.20 mg/mLLinalool (30.80%), linalyl acetate (31.30%) [140]
P. aeruginosa (ATCC 9027)8.60 mg/mL
P. aeruginosa (ATCC 27858)2.00 mg/mLLinalyl acetate (36.70%), linalool (31.40%), terpinen-4-ol (14.90%)[99]
Lavandula dentata (French lavender)E. coli (BNI 2)5% DMSO2.20 mg/mLCamphor (12.40%)[141]
Lavandula officinalis (lavender)P. aeruginosaDMSO16.00 μg/mL-3-Carene (17.14%), -fenchene (16.79%), diethyl phthalate (13.84%)[118]
Lavandula stoechas (French lavender)E. coli (STCC 471)Tween 808.00 μL/mL10s,11s-Himachala-3(12),4-diene (23.62%), cubenol (16.19%)[142]
Lavandula stoechas (French lavender), flowerE. coli (NRRL B-3008)20% DMSO250.00 μg/mL-Fenchone (39.20%) [47]
P. aeruginosa (NRRL B-23)
Lavandula stoechas (French lavender), leafE. coli (NRRL B-3008)250.00 μg/mL-Fenchone (41.90%), 1,8-cineole (15.60%), camphor (12.10%)
P. aeruginosa (NRRL B-23)500.00 μg/mL

Leptospermum scoparium (manuka)MACE. coli (ATCC 11229)Tween 802.00% v/v(−)-(E)-Calamenene (14.50%), leptospermone (17.60%) [137]
P. aeruginosa (ATCC 15442)0.85% v/v
MICP. aeruginosa (ATCC 9027)Acetone4.00 mg/mLEudesma-4(14),11-diene (6.20–14.50%), -selinene (5.90–13.50%), ()-methyl cinnamate (9.20–19.50%)[138]

Litsea cubeba (May Chang)MICP. aeruginosa (ATCC 27858)Acetone1.50 mg/mLGeranial (45.60%), nerol (31.20%)[99]
Matricaria chamomilla (German chamomile)4.00 mg/mLBisabolene oxide A (46.90%), -farnesene (19.20%)[99]

Matricaria recutita (German chamomile) ADM90P. aeruginosa (ATCC 27853 and 15 clinical isolates)Tween 8054.40 mg/mLChamazulene (31.48%), -bisabolol (15.71%), bisabolol oxide (15.71%) [119]
E. coli (ATCC 25922 and 15 clinical isolates)

Matricaria songarica (chamomile)MICE. coli (CCTCC AB91112) Tween 80100 μg/mL--Farnesene (10.58%), bisabolol oxide A (10.46%) [143]
P. aeruginosa (CCTCC AB93066)200.00 μg/mL

Melaleuca alternifolia (tea tree) MICE. coli (ATCC 10536)Tween 800.12% v/vNCR [147]
E. coli (110 clinical isolates)0.12–0.25% v/v
E. coli (AG100)n.m.0.25% (v/v)Terpinen-4-ol (39.80%), -terpinene (17.80%)[149, 150]
E. coli (ATCC 25922)None used0.25% (v/v)Terpinen-4-ol (40.00%), -terpinen (13.00%), p-cymene (13.00%)[97]
E. coli (ATCC 11775)Acetone3.70 mg/mLTerpinen-4-ol (38.60%), -terpinene (21.60%)[140]
MACE. coli (ATCC 11229)Tween 800.25% v/v-Terpinene (11.40%), -terpinene (22.50%), terpinen-4-ol (35.20%) [137]
P. aeruginosa (ATCC 15442)1.00% v/v
MICP. aeruginosa (NCTC 6749)n.m.8.00% (v/v)Terpinen-4-ol (39.80%), -terpinene (17.80%)[150]
P. aeruginosa (10 clinical isolates)Tween 802.00–5.00% v/vterpinen-4-ol (35.70%)[152]
ADMP. aeruginosa (NCTC 6750)0.5% Tween 202.00% v/v Terpinen-4-ol (42.80%), -terpinene (18.20%)[115]
E. coli (NCTC 8196)0.20% v/v[115]
MICP. aeruginosa (NCIB 8295)n.m.12.50% v/vNCR[145]
MIC90P. aeruginosa (30 clinical isolates)Tween 804.00%Terpinen-4-ol (40.30%), -terpinene (19.70%)[234]
MICP. aeruginosa (ATCC 9027)Acetone8.60 mg/mLTerpinen-4-ol (38.60%), -terpinene (21.60%)[140]
MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mLTerpinen-4-ol (49.30%), -terpinene (16.90%)[99]

Melaleuca cajuputi (cajuput)MICE. coli (ATCC 25922)Tween 805.00 mg/mL1,8-Cineol (67.60%) [128]
P. aeruginosa (ATCC 27853)
P. aeruginosa (ATCC 15442)1.90% v/v1,8-Cineole (55.50%) [137]
E. coli (ATCC 11229)0.40% v/v

Melaleuca quinquenervia (niaouli)MICE. coli (ATCC 11229)Tween 800.40% v/v 1,8-Cineole (61.20%) [137]
P. aeruginosa (ATCC 15442)1.90%v/v
Melaleuca viridiflora (niaouli)P. aeruginosa (ATCC 27858)Acetone2.00 mg/mL1,8-Cineole (45.90%), -terpinene (21.00%)[99]

Melissa officinalis (lemon balm) MICP. aeruginosa (NCTC 1662)10% DSMO1000.30 μg/mLCitronellal (20.50%), -citronellol (11.50%), geraniol (17.00%) [139]
E. coli (ATCC 8739)442.30 μg/mL
E. coli (ampicillin-resistant NCTC 10418)567.40 μg/mL
E. coli (ATCC 25922)n.m.10.00 mg/mLNCR[85]

Mentha piperita (peppermint)MICE. coli (ATCC 25922)Tween 800.6 mg/mL1,8-Cineol (12.06%), menthone (22.24%), menthol (47.29%)[128]
MACE. coli (clinical isolate and MTCC 424)Sodium taurocholate1.66–2.50 μL/mLMenthol (36.40%)[125, 126]
MICE. coli (ATCC 11775)Acetone5.70 mg/mLMenthone (18.20%), menthol (42.90%)[140]
E. coli (ATCC 25922)DMSO1.25–2.50 mg/mLMenthol (27.50–42.30%), menthone (18.40–27.90%)[155]
n.m.3.20 mg/mLNCR[85]
P. aeruginosa (ATCC 27853)Tween 8020.00 mg/mL1,8-Cineol (12.06%), menthone (22.24%), menthol (47.29%)[128]
P. aeruginosaDMSO≤1.00 μg/mLMenthone (40.82%), carvone (24.16%)[118]
P. aeruginosa (ATCC 9027)0.10% v/vNCR[129]
MACP. aeruginosa (MTCC 424 and clinical isolate VR 6)Sodium taurocholate10.00–20.00 μL/mLMenthol (36.40%)[125, 126]
MICP. aeruginosa (ATCC 9027)Acetone8.60 mg/mLMenthone (18.20%), menthol (42.90%)[140]
P. aeruginosa (ATCC 27853)DMSO2.50–5.00 mg/mLMenthol (27.50–42.30%), menthone (18.40–27.90%)[155]
P. aeruginosa (ATCC 27858)Acetone2.00 mg/mLMenthol (47.50%), menthone (18.60%)[99]
E. coli (CIP 105182)Ethanol40.0 mg/mL Menthol (39.30%), menthone (25.20%) [156]
P. aeruginosa (CRBIP 19.249)0.5% ethanol80.00 mg/mL

Myrtus communis (myrtle) MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mLMyrtenyl acetate (28.20%), 1,8-cineole (25.60%), -pinene (12.50%)[99]
ADME. coli (ATCC 35218)Tween 2011.20 mg/mLNCR[157]

Ocimum basilicum (basil)MICE. coli (CIP 105182)Ethanol8.30 mg/mLLinalool (57.00%), eugenol (19.20%)[156]
MACE. coli (ATCC 8739)n.m.1.25 μL/mLEugenol (62.60%), caryophyllene (21.51%)[62]
ADME. coli (ATCC 25922)96% ethanol8.00 μL/mLEstragole (86.4%) [223]
E. coli (ESBL+) (4 clinical strains from wounds)8.50–9.25 μL/mL
E. coli (ESBL−) (4 clinical strains from wounds)10.00–11.50 μL/mL
MICP. aeruginosa (CRBIP 19.249)0.5% ethanol80.00 mg/mLLinalool (57.00%), eugenol (19.20%)[156]
MACP. aeruginosa (ATCC 9027)Tween 800.0030% v/vLinalool (54.95%), methyl chavicol (11.98%) [158]
P. aeruginosa (clinical isolate)
MICP. aeruginosa (ATCC 27858)Acetone2.67 mg/mLLinalool (54.10%)[99]
MIC90E. coli (ATCC 8739)n.m.160.00 μg/mLMethyl chavicol (46.90%), geranial (19.10%), neral (15.15%)[159]
MICE. coli (ATCC 35210) Tween 800.18–5.40 μg/mLLinalool (30.30–58.60%) [160]
P. aeruginosa (ATCC 27853)0.11–11.74 μg/mL

Origanum acutidens (Turkey oregano)MICE. coli (A1)10% DMSO62.50 μg/mLCarvacrol (72.00%) [161]
P. aeruginosa (ATCC9027)125.00 μg/mL
P. aeruginosa (ATCC27859)125.00 μg/mL
Origanum majorana (marjoram)P. aeruginosa (ATCC 9027)DMSO0.05% v/vNCR[129]
P. aeruginosa (ATCC 27858)Acetone2.00 mg/mL1,8-Cineole (46.00%), linalool (26.10%)[99]
Origanum microphyllum (oregano)P. aeruginosa (ATCC 227853)Tween 80NITerpin-4-ol (24.86%), -terpinene (13.83%), linalool (10.81%) [162]
E. coli (ATCC 25922)3.35 mg/mL
Origanum scabrum (oregano)E. coli (ATCC 25922)0.28 mg/mLCarvacrol (74.86%)
P. aeruginosa (ATCC 227853)1.27 mg/mL

Origanum vulgare (oregano) MACE. coli (ATCC 25922)75% ethanol200.00 mg/LNCR [231]
E. coli (10 clinical isolates)200.00–400.00 mg/L
E. coli (ATCC 8739)n.m.0.63 μL/mLCarvacrol (30.17%), -cymene (15.20%), -terpinen (12.44%)[62]
ADME. coli (ATCC 35218)Tween 200.70 mg/mLNCR[157]
MICP. aeruginosa (ATCC 27853)75% ethanol800.00 mg/L [231]
P. aeruginosa (clinical isolate)400.00 mg/L
P. aeruginosa (ATCC 2730)n.m.1648.00 mg/L[164]
P. aeruginosa (ATCC 9027)DMSO0.20% v/v[129]
Origanum vulgare subsp. hirtum (Greek oregano)MICE. coli (ATCC 25922)10% DMSO and Tween 80512.00 μg/mLLinalool (96.31%) [165]
P. aeruginosa (ATCC 27853)
Origanum vulgare subsp. vulgare (oregano)E. coli (ATCC 25922)213.30 μg/mLThymol (58.31%), carvacrol (16.11%), -cymene (13.45%)
P. aeruginosa (ATCC 27853)256.00 μg/mL

Pelargonium graveolens (geranium)ADME. coli (ATCC 25922)10% DMSO6.40 mg/mLNCR[80]
E. coli (ATCC 35218)Tween 205.60 mg/mL[157]
MICE. coli (clinical strains isolated from wounds)Ethanol3.00–3.75 mL/mLCitronellol (26.70%), geraniol (13.40%)[166]
ADMP. aeruginosa (ATCC 27853)10% DMSO12.80 mg/mLNCR[80]
MICP. aeruginosaEthanol9.25–10.50 mL/mL.Citronellol (26.70%), geraniol (13.40%)[166]

Pelargonium odoratissimum (geranium)MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mLCitronellol (34.20%), geraniol (15.70%)[99]

Perovskia abrotanoides (Russian sage)MICE. coli (ATCC 8739)10% DMSO8.00 μL/mLCamphor (23.00%), 1,8-cineole (22.00%), -pinene (12.00%) [167]
P. aeruginosa (ATCC 9027)

Pimpinella anisum (anise)MICE. coliDMSO500.00 μg/mLNCR [168]
P. aeruginosa
P. aeruginosa16.00 μg/mLAnethole (64.82%)[118]

Pinus sylvestris (pine) MICP. aeruginosa (ATCC 27858)Acetone2.00 mg/mLBornyl acetate (42.30%), camphene (11.80%), -pinene (11.00%)[99]
Piper nigrum (black pepper)P. aeruginosa (ATCC 27858)Acetone2.00 mg/mL-Caryophyllene (33.80%), limonene (16.40%)[99]

Pogostemon cablin (patchouli)MICE. coli (ampicillin-resistant NCTC 10418)10% DSMO530.2 μg/mL-Guaiene (13.80%), -bulnesene (17.10%), patchouli alcohol (22.70%) [139]
E. coli (ATCC 8739)410.7 μg/mL
P. aeruginosa (NCTC 1662)1200.00 μg/mL
Pogostemon patchouli (patchouli)P. aeruginosa (ATCC 27858)Acetone2.00 mg/mLPatchouli alcohol (37.30%), -bulnesene (14.60%), -guaiene (12.50%)[99]

Rosmarinus officinalis (rosemary)MICE. coli (ATCC 8739)Tween 800.25% v/v1,8-Cineole (27.23%), -pinene (19.43%), camphor (14.26%), camphene (11.52%)[169]
E. coli (ATCC 8739) 10% DSMO733.70 μg/mL1,8-Cineol (29.20%), (+)-camphor (17.20%) [139]
E. coli (ampicillin-resistant NCTC 10418)810.70 μg/mL
E. coli (ATCC 8739)Tween 800.03% (v/v)1,8-Cineole (26.54%), -pinene (20.14%), camphene (11.38%), camphor (12.88%)[170]
E. coli (MTCC 723)n.m.11.00 mg/mLNCR[171]
E. coli (ATCC 8739)Hexane0.47–3.75 mg/mL-Pinene (8.14–11.47)%, 1,8-cineole (10.56–11.91%), camphor (16.57–16.89%), verbenone (17.43–23.79%), bornyl acetate (9.19–11.62%)[171]
ADME. coli (ATCC 25922)10% DMSO6.40 mg/mL NCR[80]
E. coli (ATCC 35218)Tween 2011.20 mg/mL[157]
MICE. coli (ATCC 11775)Acetone4.50 mg/mL1,8-Cineole (41.40%), -pinene (13.30%), camphor (12.40%)[140]
ADME. coli (ATCC 25922)96% ethanol18.50 μL/mL1,8-Cineole (46.40%), camphor (11.40%), -pinene (11.00%) [223]
E. coli (ESBL+) (4 clinical strains from wounds)18.50–19.25 μL/mL
E. coli (ESBL−) (4 clinical strains from wounds)18.25 μL/mL–20.0 μL/mL
MICP. aeruginosa (ATCC 27853)Tween 801.00%v/v1,8-Cineole (27.23%), -pinene (19.43%), camphor (14.26%), camphene (11.52%)[169]
P. aeruginosa (NCTC 1662)10% DSMO1113.30 μg/mL1,8-Cineol (29.20%), (+)-camphor (17.20%)[139]
P. aeruginosa (ATCC 27853)Tween 800.10% v/v1,8-Cineole (26.54%), -pinene (20.14%), camphene (11.38%), camphor (12.88%)[170]
P. aeruginosa (MTCC 741)n.m.11.00 mg/mLNCR[171]
P. aeruginosa (ATCC 9027)DMSO0.20% v/v[129]
ADMP. aeruginosa (ATCC 27853)10% DMSO6.40 mg/mLNCR[80]
MICP. aeruginosa (ATCC 9027) Acetone6.20 mg/mL1,8-Cineole (41.40%), -pinene (13.30%), camphor (12.40%)[140]
P. aeruginosa (ATCC 27858)2.00 mg/mL1,8-Cineole (48.00%)[99]
ADM90P. aeruginosa (ATCC 27853 and 15 clinical isolates)Tween 8079.91 mg/mLCamphor (27.51%), limonene (21.01%), myrcene (11.19%), -pinene (10.37%) [119]
E. coli (ATCC 25922 and 15 clinical isolates)79.35 mg/mL

Salvia bracteata (sage)MICE. coli (ATCC 25922)Tween 20>100.00 μg/mLCaryophyllene oxide (16.60%) [173]
MACP. aeruginosa (ATCC 27853)

Salvia eremophila (sage)MICE. coli (ATCC 10536)10% DMSO500.00 μg/mLBorneol (21.83%), -pinene (18.80%), bornyl acetate (18.68%) [174]
P. aeruginosa (ATCC 27853)NI

Salvia nilotica (sage) ADME. coli (ATCC 25922)n.m.NItrans-Caryophyllene (10.90%) [175]
P. aeruginosa (ATCC 227853)7.80 mg/mL

Salvia officinalis (sage)ADME. coli (ATCC 35218)Tween 2011.2 mg/mLNCR[157]
MICE. coli (ATCC 8739)10% DSMO475.0 μg/mL1,8-Cineol (27.40%), -thujone (16.30%), -thujone (11.20%), borneol (10.40%) [139]
E. coli (ampicillin-resistant NCTC 10418)548.0 μg/mL
P. aeruginosa (NCTC 1662)1250.30 μg/mL
P. aeruginosa (ATCC 9027)DMSO0.20% v/vNCR[129]
ADMP. aeruginosa (clinical strain)n.m.7.50 mg/mLNCR [176]
E. coli (ATCC 25922)3.75 mg/mL
E. coli (clinical strain)7.50 mg/mL

Salvia ringens (sage)MICE. coli (ATCC 25922)n.m.3.25 mg/mL-Pinene (12.85%), 1,8-cineole (46.42%) [177]
P. aeruginosa (ATCC 227853)3.75 mg/mL
Salvia rosifolia (sage) (3 samples)E. coli (NRRL B 3008)20% DMSO250–1000 μg/mL-Pinene (15.70–34.80%), 1,8-cineole (16.60–25.10%), -pinene (6.70–13.50%) [178]
P. aeruginosa (NRRL B 23)250.00–500.00 μg/mL
Salvia rubifolia (sage)E. coli (ATCC 25922)Tween 20100 μg/mL-Muurolene (11.80%).[173]

Salvia sclarea (clary sage)MICP. aeruginosa (ATCC 27858)Acetone3.50 mg/mLLinalyl acetate (72.90%), linalool (11.90%) [99]
Santalum album (sandalwood)0.50 mg/mL-Santalol (32.10%)
Styrax benzoin (benzoin)3.00 mg/mLCinnamyl alcohol (44.80%), benzene propanol (21.70%)

Syzygium aromaticum (clove) MICE. coli (ATCC 8739)Tween 800.50% v/vEugenol (68.52%), -caryophyllene (19.00%), 2-methoxy-4-[2-propenyl]phenol acetate (10.15%)[169]
ADME. coli (ATCC 25922)10% DMSO1.6 mg/mLNCR[80]
MICP. aeruginosa (ATCC 27853)Tween 800.13% v/vEugenol (68.52%), -caryophyllene (19.00%), 2-methoxy-4-[2-propenyl]phenol acetate (10.15%)[169]
ADMP. aeruginosa (ATCC 27853)10% DMSO1.60 mg/mLNCR[80]
MICP. aeruginosaDMSO16.00 μg/mLEugenol (84.07%), isoeugenol (10.39%)[118]
P. aeruginosa (ATCC 27858)Acetone1.50 mg/mLEugenol (82.20%), eugenol acetate (13.20%)[99]

Tagetes minuta (Mexican marigold)MIC90E. coli (ATCC 8739)n.m.165.00 μg/mLDihydrotagetone (33.90%), -ocimene (19.90%), tagetone (16.10%)[159]

Tagetes patula (French marigold)MICP. aeruginosa (ATCC 27858)Acetone1.50 mg/mL( )--Ocimene (41.30%), -tagetone (11.20%), verbenone (10.90%)[99]

Thymus capitatus (thyme)MICE. coli (ATCC 25922)Tween 80900.00 μg/mL-Cymene (26.40%), thymol (29.30%), carvacrol (10.80%) [181]
P. aeruginosa (ATCC 27853)900.00 μg/mL
Thymus capitatus (thyme), commercialE. coli (ATCC 25922)900.00 μg/mL-Pinene (25.20%), linalool (10.30%), thymol (46.10%)
P. aeruginosa (ATCC 27853)900.00 μg/mL
Thymus herba-barona (thyme), GennargentuE. coli (ATCC 25922)450 μg/mLThymol (46.90%), carvacrol (20.60%)
P. aeruginosa (ATCC 27853)900.00 μg/mL
Thymus herba-barona (thyme), LimbaraE. coli (ATCC 25922)450 μg/mL-Cymene (27.60%), thymol (50.30%)
P. aeruginosa (ATCC 27853)900.00 μg/mL

Thymus hyemalis (thymol, thymol/linalool, carvacrol chemotypes) (thyme)MACE. coli (CECT 516)95% ethanol<0.2–2.0 μL/mL-Cymene (16.00–19.80%), linalool (2.10–16.60%), thymol (2.90–43.00%), carvacrol (0.30–40.10%)[61]

Thymus numidicusADMP. aeruginosa (clinical strain)n.m.0.47 mg/mLNCR [176]
E. coli (ATCC 25922)0.12 mg/mL
E. coli (clinical strain)0.23 mg/mL

Thymus schimperi (thyme)ADME. coliDMSO0.63 μL/mLNCR[232]
Thymus serpyllum (thyme)E. coli (ATCC 35218)Tween 200.70 mg/mL[157]

Thymus vulgaris (thyme) MICE. coliDMSO62.50 μg/mLNCR[168]
E. coli (ATCC 8739)10% DSMO430.40 μg/mLp-Cymene (17.90%), thymol (52.40%) [139]
E. coli (ampicillin-resistant NCTC 10418)360.60 μg/mL
E. coli (ATCC 25922)n.m.0.30 mg/mLNCR[85]
ADME. coli (ATCC 25922)Ethanol0.25 μL/mLThymol (38.10%), -cymene (29.10%) [182]
E. coli (2 multidrug-resistant clinical strains from groin)0.25–0.50 μL/mL
E. coli (7 multidrug-resistant clinical strains from wounds)
E. coli (multidrug-resistant clinical strain from abdominal cavity)0.50 μL/mL
E. coli (2 multidrug-resistant clinical strains from ulcers)0.25–0.50 μL/mL
E. coli (5 multidrug-resistant clinical strains from bedsores)
MICE. coli (ATCC 11775)Acetone0.50 mg/mLThymol (47.20%), -cymene (22.10%)[140]
ADME. coli (ATCC3428)Tween 209.25 μg/mLThymol (48.10%), -cymene (15.60%), -terpinene (15.40%)[81]
MICP. aeruginosaDMSO500.00 μg/mLNCR[168]
P. aeruginosa (NCTC 1662)10% DSMO1250.30 μg/mL-Cymene (17.90%), thymol (52.40%)[139]
ADMP. aeruginosa (ATCC 27853)Ethanol0.50 μL/mLThymol (38.10%), -cymene (29.10%) [182]
P. aeruginosa (multidrug-resistant clinical strain from toes)1.50 μL/mL
P. aeruginosa (6 multidrug-resistant clinical strains from wounds)1.50–2.00 μL/mL
P. aeruginosa (6 multidrug-resistant clinical strains from ulcers)2.00–2.50 μL/mL
P. aeruginosa (6 multidrug-resistant clinical strains from bedsores)1.50–2.00 μL/mL
MICP. aeruginosa (ATCC 9027)Acetone8.6. mg/mLThymol (47.20%), -cymene (22.10%)[140]
P. aeruginosa (ATCC 27858)2.00 mg/mL-Cymene (39.90%), thymol (20.70%)[99]

Thymus vulgaris (thyme) (thymol chemotype) MACE. coli (CECT 516) 95% ethanol0.5 μL/mL-Cymene (18.70%), thymol (57.70%) [61]
Thymus zygis subsp. gracilis (thyme) (thymol and two linalool chemotypes)<0.2 μL/mL-Cymene (0.50–11.20%), ()-sabinene hydrate (0.20–18.20%), linalool (2.00–82.30%)

Vetiveria zizanioides/Andropogon muricatus (vetiver)MICP. aeruginosa (ATCC 27858)Acetone1.50 mg/mLZizanol (13.60%), -vetirenene (7.20%)[99]

name (common name), part of plant (if applicable).
: microdilution method; MAC: macrodilution method; ADM: agar dilution method; CTA: contact time assay.
Type Culture Collection, Rockville, USA (ATCC); Colección Espanõla de Cultivos Tipo (CECT); collection of microorganisms of the Department of Microbiology (MFBF); culture collection of antibiotics-resistant microbes (CCRM); Eskişehir Osmangazi University, Faculty of Medicine, clinical isolate (OGU); Laboratorio de Microbiología, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina (LM); Microbial Type Culture Collection (MTCC); Mycology Laboratory (LM); National Center of Industrial Microorganisms (NCIM); National Collection of Type Cultures, London, Great Britain (NCTC); Spanish Collection of Type Cultures (STCC).
concentration was not included; n.m.: not mentioned.
: no inhibition.
: no composition results reported.

Aniba rosaeodora (rosewood) was found to inhibit E. coli at an MIC value of 0.40 mg/mL. No GC-MS data was given [85]. Anthemis aciphylla var. discoidea (chamomile) also displayed notable inhibition against E. coli and P. aeruginosa; however, the highest activity was seen for the essential oil containing high levels of α-pinene (39.00%) and terpinen-4-ol (32.10%) [114]. Cinnamomum zeylanicum, with the main compound cinnamaldehyde, was shown to have inhibited these two Gram-negative pathogens at noteworthy MIC values [80]. Noteworthy activity was also reported for Commiphora myrrha (myrrh) and Thymus numidicus (thyme) [99]. Syzygium aromaticum and S. album were reported to effectively inhibit P. aeruginosa [99]; and Thymus vulgaris (thyme) inhibits E. coli (including multidrug-resistant strains) [182].

4.1.4. Other Bacterial Pathogens

Brevibacterium spp. form part of the Coryneform bacteria and are involved in foul body odour [3, 103]. Insufficient quantitative studies have been conducted using commercial essential oils to treat problems caused by these microorganisms, even though there have been some earlier studies using the diffusion assays against B. linen [226228]. One quantitative study reported on the activity of Ziziphora persica against B. agri (125 μg/mL) and B. brevis (250 μg/mL), in addition to Ziziphora clinopodioides against B. agri (31.25 μg/mL) and B. brevis (125 μg/mL) [229]. In another study, essential oils of Kunzea ericoides (Kānuka) and L. scoparium were able to inhibit three species of Brevibacterium (MIC: 0.06–1.00 mg/mL) [138]. Clearly, the lack of attention to this neglected group of microorganisms warrants further attention, especially considering that, to the best of our knowledge, not one essential oil recommended for odour has been investigated against relevant pathogens in vitro.

The β-hemolytic Streptococcus (S. pyogenes) is a threatening pathogen that needs to be considered when investigating wound infections [166]. Group A Streptococcus (GAS) is usually involved in impetigo and necrotising fasciitis (“flesh-eating” disease). This pathogen has developed resistance to erythromycin, azithromycin, clarithromycin, clindamycin, and tetracycline [188, 190]. Group B Streptococcus is also involved in skin infections and has developed resistance to clindamycin, erythromycin, azithromycin, and vancomycin [190]. Periorbital cellulitis is a common occurrence in children and is caused by Haemophilus influenzae [106], and Clostridium spp. (C. perfringens, C. septicum, C. tertium, C. oedematiens, and C. histolyticum) are involved in gas green/gangrene infections. Table 6 summarises the antimicrobial activity of essential oils that have been studied and shown to have some in vitro efficacy against these pathogens. The lack of studies against S. pyogenes, C. perfringens, and H. influenza highlights the need to investigate these sorely neglected dermatologically important pathogens, especially since the few available studies have shown these organisms to be highly susceptible to essential oil inhibition. These are also pathogens that cause deeper skin infections, so, with the enhanced penetration offered by essential oils, they may prove beneficial.

Essential Species Main Reference

Achillea millefolium (yarrow)MICC. perfringens KUKENS-TurkeyTween 804.50 mg/mLEucalyptol (24.60%), camphor (16.70%), α-terpineol (10.20%)[112]
Achillea setacea (bristly yarrow)0.56 mg/mLSabinene (10.80%), eucalyptol (18.50%) [113]
Achillea teretifolia (yarrow)0.28 mg/mLEucalyptol (19.90%), camphor (11.10%), borneol (11.90%)

Eucalyptus globulus (eucalyptus)MICS. pyogenes (ATCC 12344)Tween 8010.00 mg/mL1,8-Cineol (81.93%) [128]
S. pyogenes (NHLS 8668)0.50 mg/mL

Eucalyptus radiata (eucalyptus)MICS. pyogenes (NHLS 8668)Acetone0.50–1.00 mg/mL1,8-Cineole , -terpineol [130]
Eucalyptus camaldulensis (eucalyptus)Acetone0.50 mg/mL
Eucalyptus citriodora (eucalyptus)Acetone1.00 mg/mL
Eucalyptus smithii (eucalyptus)Acetone0.50 mg/mL
Eucalyptus dives (eucalyptus)Acetone

Juniperus excelsa (juniper), berries, DojranADMS. pyogenes (clinical isolate)50% DSMO>50.00%-Pinene (70.81%) [87]
H. influenzae (clinical isolate)31.00 μL/mL
Juniperus excelsa (juniper), berries, OhridS. pyogenes (clinical isolate)>50.00%Sabinene (58.85%)
H. influenzae (clinical isolate)
Juniperus excelsa (juniper), leaves, DojranH. influenzae (clinical isolate)>50.00%-Pinene (33.83%), cedrol (24.44%)
Juniperus excelsa (juniper), leaves, OhridS. pyogenes (clinical isolate)125.00 μL/mLSabinene (29.49%), cis-thujone (26.20%), menth-2-en-1-ol (12.86%)
H. influenzae (clinical isolate)

Juniperus officinalis (juniper berry)MICS. pyogenes (ATCC 12344)Tween 8020.00 mg/mL-Pinene (39.76%)[128]

Kunzea ericoides (Kānuka)MACC. diphtheriae (clinical isolate)Tween 800.25% v/v-Pinene (61.60%) [137]
C. minutissimus (clinical isolate)0.30% v/v
MICS. pyogenes (ATCC 8668)Acetone2.00 mg/mL-Pinene (26.2–46.7%), p-cymene (5.8–19.1%) [138]
B. brevis (ATCC 8246)1.00 mg/mL
B. agri (ATCC 51663)
B. laterosporus (ATCC 64)

Leptospermum scoparium (manuka)MACC. diphtheriae (clinical isolate)Tween 800.05% v/v(−)-()-Calamenene (14.50%), leptospermone (17.60%) [137]
C. minutissimus (clinical isolate)
MICS. pyogenes (ATCC 8668)Acetone1.00 mg/mLEudesma-4(14),11-diene (6.2–14.5%), -selinene (5.90–13.5%), ()-methyl cinnamate (9.2–19.5%) [138]
B. brevis (ATCC 8246)
B. agri (ATCC 51663)0.06 mg/mL
B. laterosporus (ATCC 64)0.25 mg/mL

Melaleuca alternifolia (tea tree)MICCorynebacterium spp. (10 clinical isolates)Tween 800.06–2% v/vTerpinen-4-ol (35.70%)[152]
MIC90S. pyogenes (15 clinical isolates)0.12%[235]
MICC. diphtheriae (clinical isolate)Tween 800.20% v/v-Terpinene (11.40%), -terpinene (22.50%), terpinen-4-ol (35.20%) [137]
C. minutissimus (clinical isolate)

Melaleuca cajuputi (cajuput)MICS. pyogenes (ATCC 12344)Tween 805.00 mg/mL1,8-Cineol (67.60%)[128]
MACC. diphtheriae (clinical isolate)0.30% v/v1,8-Cineole (55.50%) [137]
C. minutissimus (clinical isolate)

Melaleuca quinquenervia (niaouli)MACC. diphtheriae (clinical isolate)Tween 800.25% v/v1,8-Cineole (61.20%) [137]
C. minutissimus (clinical isolate)

Mentha piperita (peppermint)MICS. pyogenes (ATCC 12344)Tween 805.00 mg/mL1,8-Cineol (12.06%), menthone (22.24%), menthol (47.29%)[128]

name (common name), part of plant (if applicable).
: microdilution method; MAC: macrodilution method; ADM: agar dilution method; CTA: contact time assay.
Type Culture Collection, Rockville, USA (ATCC).
concentration was not included; n.m.: not mentioned.
: no inhibition.
: no composition results reported.
4.1.5. Fungal Infections: Yeasts

Yeasts may act as opportunistic pathogens and can result in infection if presented with the opportunity, the most common pathogen being Candida albicans. Candida spp. can cause candidiasis at several different anatomical sites [230]. Candida has started developing resistance to first-line and second-line antifungal treatment agents such as fluconazole [190]. Essential oils demonstrating noteworthy activity against this organism are shown in Table 7. Candida albicans has been quite extensively investigated and most oils used in dermatology have been tested against this pathogen.

Essential Species Main Reference

Abies balsamea (fir) MICC. albicans (ATCC 10231)Acetone2.00 mg/mL-Pinene (31.00%), bornyl acetate (14.90%), -3-carene (14.20%)[99]
Abies holophylla (Manchurian fir)C. albicans (B02630)DMSO>2.20 mg/mLBicyclo[2.2.1]heptan-2-ol (28.05%), -3-carene (13.85%), -pinene (11.68%), camphene (10.41%) [111]
Abies koreana (Korean fir)Bornyl ester (41.79%), camphene (15.31%), α-pinene (11.19%)

Achillea millefolium subsp. millefolium (yarrow)MICC. albicans (ATCC 10239)Tween 804.50 mg/mLEucalyptol (24.60%), camphor (16.70%), -terpineol (10.20%)[112]
Achillea setacea (bristly yarrow)1.12 mg/mLSabinene (10.80%), eucalyptol (18.50%)[113]

Angelica archangelica (angelica) rootMICC. albicans (ATCC 10231)Acetone2.00 mg/mLα-Phellandrene (18.50%), α-pinene (13.70%), -phellandrene (12.60%), -3-carene (12.10%) [99]
Angelica archangelica (angelica) seed-Phellandrene (59.20%)

Anthemis nobilis (chamomile)MICC. albicans (ATCC 10231)Acetone3.00 mg/mL2-Methylbutyl-2-methyl propanoic acid (31.50%), limonene (18.30%), 3-methylpentyl-2-butenoic acid (16.70%), isobutyl isobutyrate (10.00%)[99]

Apium graveolens (celery)ADM90C. albicans (ATCC 10231)Tween 801.00% v/vNCR[236]
Artemisia dracunculus (tarragon)MICAcetone2.00 mg/mLEstragole (82.60%)[99]

Boswellia carteri (frankincense)ADM90C. albicans (ATCC 10231)Tween 801.00% v/vNCR[236]
Boswellia carteri (frankincense) (9 samples) MIC Acetone5.30–12.00 mg/mL-Pinene (4.80–40.40%), myrcene (1.60–52.40%), limonene (1.90–20.40%), -thujene (0.30–52.40%), -cymene (2.70–16.90%), -pinene (0.30–13.10%) [116]
Boswellia frereana (frankincense) (3 samples)6.00–12.00 mg/mL-Pinene (2.00–64.70%), -thujene (0.00–33.10%), -cymene (5.40–16.90%)
Boswellia neglecta (frankincense)1.80 mg/mLNCR[117]
6.60 mg/mL-Pinene (43.40%), -pinene (13.10%)[116]
Boswellia papyrifera (frankincense)1.40 mg/mLNCR [117]
Boswellia rivae (frankincense)4.00 mg/mL
Boswellia sacra (frankincense) (2 samples)8.00 mg/mL-Pinene (18.30–28.00%), -thujene (3.90–11.20%), limonene (11.20–13.10%) [116]
Boswellia spp. (frankincense) (4 samples)6.00–8.00 mg/mL-Pinene (18.80–24.20%), limonene (11.70–19.00%)
Boswellia thurifera (frankincense)6.00 mg/mL-Pinene (28.00%), limonene (14.60%)

Cananga odorata (ylang-ylang)ADM90C. albicans (ATCC 10231)Tween 801.00% v/vNCR[236]
MICAcetone2.00 mg/mLBicyclosesquiphellandrene (19.50%), -farnesene (13.90%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 200.25–0.50%NCR[237]
Cananga odorata (ylang-ylang) headsMICC. albicans (ATCC 10231)Acetone2.00 mg/mLBenzyl acetate (31.90%), linalool (27.00%), methyl benzoate (10.40%)[99]

Canarium luzonicum (elemi)MICC. albicans (ATCC 10231)Acetone3.00 mg/mLLimonene (41.90%), elemol (21.60%), -phellandrene (11.40%)[99]

Carum carvi (caraway)MICC. albicans (ATCC 10231)Acetone2.00 mg/mLLimonene (27.60%), carvone (67.50%)[99]

Carum carvi (caraway)MICC. albicansDMSO≤1.00 μg/mLDL-Limonene (53.35%), -selinene (11.08%), -elemene (10.09%)[118]

Cedrus atlantica (cedar wood)ADM90C. albicansTween 802.00% v/vNCR[236]

Cinnamomum camphora (camphor)ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 200.50%NCR[237]

Cinnamomum cassia (cinnamon)MAC80C. albicans (ATCC90029)n.m.0.17 μL/mLtrans-Cinnamaldehyde (92.20%)[238]

Cinnamomum cassia (cinnamon)MICC. albicansDMSO≤1.00 μg/mLtrans-Caryophyllene (17.18%), eugenol (14.67%), linalool L (14.52%), trans-cinnamyl acetate (13.85%), cymol (11.79%), cinnamaldehyde (11.25%)[118]

Cinnamomum zeylanicum (cinnamon)ADMC. albicansDMSO0.08 μL/mLNCR[232]
MICC. albicans (ATCC 10231)Acetone2.00 mg/mLEugenol (80.00%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 200.01%NCR[237]

Citrus aurantium (petitgrain)ADM90C. albicans (ATCC 10231)Tween 800.25% v/vNCR[236]
MICAcetone2.00 mg/mLLinalyl acetate (54.90%), linalool (21.10%)[99]

Citrus bergamia (bergamot)ADM90C. albicans (ATCC 10231)Tween 801.00% v/v NCR[236]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 201.00–2.00%[237]

Citrus grandis (grapefruit)MICC. albicans (ATCC 10231)Acetone2.00 mg/mLLimonene (74.80%)[99]

Citrus medica limonum (lemon)ADM90C. albicans (ATCC 10231)Tween 802.00% v/v NCR[236]
ADMC. albicansDMSO2.50 μL/mL[232]
MICC. albicans (ATCC 10231)Acetone2.00 mg/mL[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 200.50–1.00%[237]

Citrus limon (lemon), aromatic artMACC. albicans (clinical strain C31)Tween 800.03%Limonene (22.42%), isopropyl myristate (42.78%) [239]
Citrus limon (lemon), Avicenna0.60%Limonene (42.03%), -pinene (15.15%)
Citrus limon (lemon) -Vera NordLimonene (23.39%), trans-citral (15.52%), cis-citral (19.41%)

Citrus sinensis (orange)MACC. albicans (ATCC 10231)0.1% ethanol3.75 mg/LNCR[121]
MICAcetone2.00 mg/mLLimonene (93.20%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 201.00%NCR[237]

Commiphora guidotti (myrrh)MICC. albicans (ATCC 10231)Acetone2.00 mg/mL( )--Ocimene (52.60%), -santalene (11.10%), ()-bisabolene (16.00%) [117]
Commiphora myrrha (myrrh)1.50 mg/mLFuranogermacrene (15.90%), furanoeudesma-1,3-diene (44.30%)
4.00 mg/mLFuranoeudesma-1,3-diene (57.70%), lindestrene (16.30%)[99]

Coriandrum sativum (coriander)ADM90C. albicans (ATCC 10231)Tween 800.25% v/vNCR[236]
MICC. albicans (CBS 562 and 4 clinical isolates)n.m.0.02–0.06 mg/mLDecanal (10.97%), 1-decanol (15.30%), 2-dodecenol (11.26%)[240]

Cupressus sempervirens (cypress)MICC. albicans (ATCC 10231)Acetone4.00 mg/mLα-Pinene (41.20%), -3-carene (23.70%)[99]

Cymbopogon citratus (lemongrass)ADM90C. albicans (ATCC 10231)Tween 800.12% v/vNCR[236]
ADMC. albicans (SP-14)Sodium taurocholate5.00 μL/mLCitral (72.80%)[125, 126]
MICC. albicans (ATCC 10231)Acetone2.00 mg/mLGeranial (44.80%)[99]
MICC. albicansDMSO≤1.00 μg/mLGeranial (47.34%), -myrcene (16.53%), Z-citral (8.36%)[118]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 200.06%NCR[237]

Cymbopogon martinii (palmarosa)MICC. albicans (CBS 562 and 4 clinical isolates)n.m.0.06–0.25 mg/mLNCR[240]
ADMC. albicans (SP-14)Sodium taurocholate2.00 μL/mLGeraniol (61.60%)[125, 126]
C. albicans (ATCC 10231 and 3 clinical isolates) Tween 200.12–0.15% NCR[237]
C. albicans (clinical samples)0.08%[75]

Cymbopogon nardus (citronella)ADM90C. albicans (ATCC10231)Tween 800.25% v/vNCR[236]
MICAcetone0.75 mg/mLCitronellal (38.30%), geraniol (20.70%), citronellol (18.80%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 200.50–1.00%NCR[237]

Cymbopogon winterianus (citronella grass)MICC. albicans (CBS 562 and 4 clinical isolates)n.m.0.50–1.00 mg/mLNCR[240]

Daucus carota (carrot seed)MICC. albicans (ATCC10231)Acetone3.00 mg/mLCarotol (44.40%)[99]
MAC 2% DSMO1.25–2.50 μL/mLSabinene (28.30–33.80%), limonene (6.50–11.80%), elemicin (6.20–26.00%)[241]
20.00 μL/mL (v/v)-Bisabolene (17.6%), carotol (25.1), 11H-himachal-4-en-1-ol (21.6%) [242]
5.00–10.00 μL/mL (v/v)-Bisabolene (51.00%), ()-methyl isoeugenol (10.00%)
-Pinene (37.9%), geranyl acetate (15%)
20.00 μL/mL (v/v)Geranyl acetate (65.00%)

Eucalyptus camaldulensis (eucalyptus)ADMC. albicansDMSO5.00 μL/mLNCR[232]

Eucalyptus fruticetorum (eucalyptus)ADM90C. albicans (ATCC10231)Tween 801.00% v/vNCR[236]

Eucalyptus globulus (eucalyptus)ADMC. albicans (clinical samples)Tween 200.05%NCR[75]
MIC90C. albicans (ATCC 90028)Tween 8010.00 mg/mL1,8-Cineol (81.93%)[128]
ADMC. albicans (SP-14)Sodium taurocholate5.00 μL/mLCineole (23.20%)[125, 126]
MICC. albicans (ATCC 10231)Acetone1.50 mg/mL1,8-Cineole (58.00%), -terpineol (13.20%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 201.50%NCR[237]
MICC. albicans (ATCC 10231)Acetone1.00 mg/mLNCR[130]

Eucalyptus radiata (eucalyptus) MICC. albicans (ATCC 10231) Acetone1.00 mg/mL1,8-Cineole , -terpineol [130]
Eucalyptus camaldulensis (eucalyptus)0.50 mg/mLNCR
Eucalyptus citriodora (eucalyptus)1.00 mg/mL
Eucalyptus smithii (eucalyptus)
Eucalyptus dives (eucalyptus)

Eucalyptus intertexta (eucalyptus)MACC. albicans (ATCC 10231)10% DSMO7.80 μg/mLNCR [131]
Eucalyptus largiflorens (eucalyptus)125.00 μg/mLNCR

Eugenia caryophyllus (clove)ADMC. albicans (clinical samples)Tween 200.33%NCR[75]
Foeniculum vulgare (fennel)MICC. albicansDMSO≤1.00 μg/mLtrans-Anethole (33.3%), DL-limonene (19.66%), carvone (12.03%)[118]
Foeniculum dulce (fennel)MICC. albicans (ATCC 10231)Acetone2.00 mg/mL-Anethole (79.10%)[99]

Hyssopus officinalis (hyssop)MICC. albicans (ATCC 10231)Acetone1.00 mg/mLIsopinocamphone (48.70%), pinocamphone (15.50%)[99]

Geranium dissectum (geranium)MICC. albicansDMSO≤1.00 μg/mL-Citronellol (25.45%), geraniol (13.83%)[118]

Jasminum nudiflorum (jasmine) ADMC. albicans (clinical samples)Tween 20>3.00%NCR[75]
Juniperi aetheroleum (juniper)MAC80C. albicans (MFBF)n.m.1.00% v/v-Pinene (29.17%), -pinene (17.84%), sabinene (13.55%)[135]
Juniperus chinensis (Chinese juniper)ADMC. albicans (clinical samples)Tween 202.00%NCR[75]
Juniperus communis (juniper berry)MIC90C. albicans (ATCC 90028)Tween 8020.00 mg/mL-Pinene (39.76%)[128]
Juniperus communis (juniper)ADM90C. albicans (ATCC10231)2.00% v/vNCR[236]
Juniperus communis ssp. alpina (juniper), berries MACC. albicans (clinical strain D5) 2% DMSO1.25–2.50 μL/mL-Pinene (77.40%) [243]
Juniperus communis subsp. alpina (juniper)C. albicans (ATCC 10231)5.00–10.00 μL/mL
2.50 μL/mLSabinene (26.20%), -pinene (12.90%), limonene (10.40%)[244]
Juniperus virginiana (juniper) MICC. albicans (ATCC 10231) Acetone1.50 mg/mLThujopsene (29.80%), cedrol (14.90%), -cedrene (12.40%) [99]
Juniperus virginiana (juniper), berries2.00 mg/mL-Pinene (20.50%), myrcene (13.70%), bicyclosesquiphellandrene (10.70%)
Juniperus virginiana (juniper)ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 203.00%NCR[237]
Juniperus turbinata (juniper), berries MACC. albicans (ATCC 10231) 2% DMSO10.00–20.00 μL/mL-Pinene (66.70%) [243]
C. albicans (clinical strain D5)5.00 μL/mL
Juniperus turbinata (juniper), leafC. albicans (ATCC 10231)2% DMSO5.00 μL/mL-Pinene (48.20%), -phellandrene (23.10%)
C. albicans (clinical strain D5)1.25 μL/mL
Juniperus oxycedrus (cade juniper)ADMC. albicans (clinical samples)Tween 20NINCR[75]

Juniperus oxycedrus ssp. oxycedrus (cade), leaf MACC. albicans (ATCC 10231)2% DMSO1.25–25.00 μL/mL-Pinene (65.50%) [243]
C. albicans (clinical strain D5)0.32–0.64 μL/mL
Juniperus oxycedrus ssp. oxycedrus (cade), berriesC. albicans (ATCC 10231)2% DMSO10.00–20.00 μL/mL-Pinene (54.70)%, myrcene (17.80%), germacrene D (10.40%)
C. albicans (clinical strain D5)5.00 μL/mL

Kunzea ericoides (Kānuka)MACC. albicans (ATCC 10231)Tween 80>2.00% v/v-Pinene (61.60%)[137]
MICC. albicans (ATCC 10231)Acetone4.00 mg/mL-Pinene (26.20–46.70%), p-cymene (5.80–19.10%)[138]
Laurus nobilis (bay)0.75 mg/mLEugenol (57.20%), myrcene (14.30%), chavicol (12.70%)[99]

Lavandula angustifolia (lavender)ADMC. albicans (clinical samples)Tween 20>3.00%NCR[75]
MICC. albicans (ATCC 10231)Acetone5.70 mg/mLLinalool (30.80%), linalyl acetate (31.30%)[140]
3.00 mg/mLLinalyl acetate (36.70%), linalool (31.40%), terpinen-4-ol (14.90%)[99]
ADM90C. albicans (ATCC 10231)Tween 800.50% v/vNCR [236]
0.25% v/v

Lavandula officinalis (lavender)MICC. albicans (ATCC 10231)DMSO≤1.00 μg/mL-3-Carene (17.14%), -fenchene (16.79%), diethyl phthalate (13.84%)[118]

Lavandula pedunculata (French lavender)MACC. albicans (ATCC 10231)2% DMSO2.50 μL/mL1,8-Cineole (2.40–55.50%), fenchone (1.30–59.70%), camphor (3.60–48.00%)[245]
Lavandula stoechas (French lavender)Fenchone (37.00%) and camphor (27.30%)[246]
Lavandula viridis (yellow lavender)1,8-Cineole (34.50%–42.2%), camphor (13.40%)[247]

Leptospermum scoparium (manuka)MACC. albicans (ATCC 10231)Tween 80>2.00% v/v(−)-()-Calamenene (14.50%), leptospermone (17.60%)[137]
MICAcetone8.00 mg/mLEudesma-4(14),11-diene (6.2–14.5%), α-selinene (5.90–13.5%), ()-methyl cinnamate (9.2–19.5%)[138]

Litsea cubeba (May Chang)MICC. albicans (ATCC 10231)Acetone6.00 mg/mLGeranial (45.60%), nerol (31.20%)[99]

Matricaria chamomilla (German chamomile)MICC. albicans (ATCC 10231)Acetone0.50 mg/mLBisabolene oxide A (46.90%), -farnesene (19.20%)[99]
ADMC. albicans (clinical samples)Tween 20NINCR[75]

Melaleuca alternifolia (tea tree)ADMC. albicans (clinical samples)Tween 200.73%NCR[75]
MICC. albicans (KEM H5)n.m.0.13% (v/v)Terpinen-4-ol (39.80%), -terpinene (17.80%)[149, 150]
ADM90C. albicans (ATCC10231)Tween 800.25% v/vNCR[236]
ADM0.20% v/vTerpinen-4-ol (42.80%), -terpinene (18.20%)[115]
MICC. albicans (NCYC 854)n.m.0.25% v/vNCR[145]
C. albicans (fluconazole- and itraconazole-susceptible isolates) Tween 800.06–0.50% v/v Terpinen-4-ol (42.35%), -terpinene (20.65%) [248]
C. albicans (fluconazole- and/or itraconazole-resistant isolates; six isolates were cross-resistant)0.25–0.50% v/v
ADMC. albicans (NRRL y-12983) n.m. 3.50 mg/mL NCR [249]
C. albicans (ATCC 14053)
C. albicans (NRRL y-869)
C. albicans (NRRL y-22077)1.75 mg/mL
C. albicans (ATCC 10231)3.50 mg/mL
MICC. albicans (NRRL 12983) 4.73 mg/mL-Terpinene (16.30%), terpinen-4-ol (30.30%) [61]
C. albicans (ATCC 14053)
C. albicans (ATCC 90028)
C. albicans (NRRL 22077)2.30 mg/mL
C. albicans (ATCC 10231)4.73 mg/mL
C. albicans (ATCC 10231)Acetone3.70 mg/mLTerpinen-4-ol (38.60%), -terpinene (21.60%)[140]
MACC. albicans (ATCC 10231)Tween 800.30% v/v-Terpinene (11.40%), -terpinene (22.50%), terpinen-4-ol (35.20%)[137]
MICC. albicans (ATCC 10231)Acetone1.50 mg/mLTerpinen-4-ol (49.30%), -terpinene (16.90%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 200.12–0.25%NCR[237]

Melaleuca cajuputi (cajuput)MIC90C. albicans (ATCC 90028)Tween 802.50 mg/mL1,8-Cineol (67.60%)[128]
MACC. albicans (ATCC10231)0.40% v/v1,8-Cineole (55.50%)[137]

Melaleuca quinquenervia (niaouli)MACC. albicans (ATCC10231)Tween 800.40% v/v1,8-Cineole (61.20%)[137]

Melaleuca viridiflora (niaouli)MICC. albicans (ATCC10231)Acetone1.75 mg/mL1,8-Cineole (45.90%), α-terpinene (21.00%)[99]

Mentha piperita (peppermint)ADM90C. albicans (ATCC10231)Tween 800.50% v/vNCR[236]
MIC90C. albicans (ATCC 90028)0.30 mg/mL1,8-Cineol (12.06%), menthone (22.24%), menthol (47.29%)[128]
ADMC. albicans (SP-14)Sodium taurocholate5.00 μL/mLMenthol (36.40%)[125, 126]
MICC. albicans (ATCC 10231)Acetone2.40 mg/mLMenthone (18.20%), menthol (42.90%)[140]
ADMC. albicans (clinical isolate)Tween 200.08%NCR[75]
MICC. albicans (clinical isolate) DMSO0.31–0.63 mg/mLMenthol (27.50–42.30%), menthone (18.40–27.90%)[155]
C. albicans≤1.00 μg/mLMenthone (40.82%), carvone (24.16%)[118]
C. albicans (ATCC 10231)Acetone2.00 mg/mLMenthol (47.50%), menthone (18.60%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 200.25–0.30%NCR[237]
Mentha pulegium (peppermint) MICC. albicans (ATCC 10231)10% DMSO1.00 μL/mLPiperitone (38.00%), piperitenone (33.00%)[250]
Mentha rotundifolia (peppermint), BejaC. albicansTween 800.80% v/vβ-Caryophyllene (26.67%), germacrene D (12.31%) [50]
Mentha rotundifolia (peppermint), BizertePulegone (32.09%), piperitenone oxide (17.28%), 5-acetyl thiazole (11.26%)

Mentha spicata (spearmint)ADM90C. albicans (ATCC 10231)Tween 800.12% v/vNCR[236]

Myrtus communis (myrtle)MICC. albicans (ATCC 10231)Acetone1.50 mg/mLMyrtenyl acetate (28.20%), 1,8-cineole (25.60%), α-pinene (12.50%)[99]
Myrtus nivellei (Sahara myrtle)MACC. albicans (ATCC 10231)2% DMSO1.25–2.50 μg/mL1,8-Cineole (37.50%), limonene (25.00%)[251]

Ocimum basilicum var. minimum (basil)MICC. albicans (ATCC 11006)DMSONILinalool (440%), 1,8-cineole (15.50%) [252]
Ocimum americanum (basil)5000.00 μg/mL1,8-Cineole (25.90%), (Z)-methyl cinnamate (29.40%)
Ocimum basilicum var. purpurascens (basil)Linalool (41.50%), α-muurolol (11.80%)
Ocimum micranthum (basil)625.00 μg/mLEugenol (64.11%), β-caryophyllene (14.30%)
Ocimum selloi1250.00 μg/mLLinalool (16.8%), anethole (52.2%)

Ocimum basilicum (basil)MICC. albicansn.m.30.00 μg/μLEstragole (45.80%), linalool (24.20%)[253]
ADM90C. albicans (ATCC10231)Tween 800.50% v/vNCR[236]
ADMC. albicans (clinical samples)Tween 201.50%[75]
MICC. albicans (ATCC 10231)Acetone1.00 mg/mLLinalool (54.10%)[99]
MIC90n.m.95.00 μg/mLMethyl chavicol (46.90%), geranial (19.10%), neral (15.15%)[159]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 201.00%NCR[237]

Ocimum gratissimum (African basil)MICC. albicans (clinical isolate)n.m.750.00 μg/mLEugenol (67.00%)[254]

Ocimum sanctum (holy basil) MIC90C. albicans (37 clinical isolates (5 resistant to fluconazole)) 10% DMSO0.10–0.24 μL/mL Methyl chavicol (44.63%), linalool (21.84%) [255]
C. albicans (ATCC 90028)0.25 μL/mL
C. albicans (ATCC 10261)0.20 μL/mL
C. albicans (ATCC 44829)
ADMC. albicans (clinical samples)Tween 200.48%NCR[75]

Origanum majorana (marjoram)MICC. albicans (ATCC 10231)Acetone2.00 mg/mL1,8-Cineole (46.00%), linalool (26.10%)[99]

Origanum acutidens (Turkey oregano)MICC. albicans (A117)10% DMSO125.00 μg/mLCarvacrol (72.00%)[161]

Origanum microphyllum (oregano)MICC. albicansTween 803.23 mg/mLTerpinen-4-ol (24.86%), -terpinene (13.83%), linalool (10.81%)[162]

Origanum vulgare (oregano)MICC. albicansn.m.2.00 μg/μLCarvacrol (61.30%), thymol (13.90%)[253]
ADM90C. albicans (ATCC10231)Tween 800.12% v/vNCR[236]
ADMC. albicans (NRRL y-12983) n.m. 0.70 mg/mL NCR [249]
C. albicans (ATCC 14053)
C. albicans (NRRL y-869)
C. albicans (NRRL y-22077)
C. albicans (ATCC 10231)
MICC. albicans (NRRL 12983)Cymene (25.00%), cymenol (58.6.00%) [61]
C. albicans (ATCC 14053)
C. albicans (ATCC 90028)
C. albicans (NRRL 22077)
C. albicans (ATCC 10231)

Origanum vulgare subsp. hirtum (Greek oregano)MACC. albicans (ATCC 10239)10% DMSO + Tween 8085.30 μg/mLLinalool (96.31%) [165]
Origanum vulgare subsp. vulgare (oregano)128.00 μg/mLThymol (58.31%), carvacrol (16.11%), -cymene (13.45%)

Pelargonium graveolens (geranium) ADMC. albicans (NRRL y-12983) n.m.0.70 mg/mLNCR [249]
C. albicans (ATCC 14053)
C. albicans (NRRL y-869)
C. albicans (NRRL y-22077)
C. albicans (ATCC 10231)
MICC. albicans (NRRL 12983) n.m. 0.12 mg/mLCitronellol (47.30%) [61]
C. albicans (ATCC 14053)
C. albicans (ATCC 90028)
C. albicans (NRRL 22077)
C. albicans (ATCC 10231)n.m.0.06 mg/mL
C. albicans (ATCC 10231)Acetone0.75 mg/mLCitronellol (34.20%), geraniol (15.70%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 200.12%NCR[237]

Perovskia abrotanoides (Russian sage)MICC. albicans (ATCC 10231)10% DMSO8.00 μL/mLCamphor (23.00%), 1,8-cineole (22.00%), α-pinene 12.00%[167]

Pimenta racemosa (West Indian bay)ADM90C. albicans (ATCC 10231)Tween 800.12% v/vNCR[236]

Pimpinella anisum (anise)MAC83C. albicansn.m.1.00% v/vAnethole, anisaldehyde, linalool[256]
MICDMSO≤1.00 μg/mLAnethole (64.82%)[118]

Pinus sylvestris (pine)MICC. albicans (ATCC 10231)Acetone1.50 mg/mLBornyl acetate (42.30%), camphene (11.80%), -pinene (11.00%)[99]

Piper nigrum (black pepper)MICC. albicans (ATCC 10231)Acetone2.00 mg/mLβ-Caryophyllene (33.80%), limonene (16.40%)[99]

Pogostemon patchouli (patchouli)MICC. albicans (ATCC 10231)Acetone1.50 mg/mLPatchouli alcohol (37.30%), α-bulnesene (14.60%), -guaiene (12.50%)[99]

Ricinus officinalis (rose)ADMC. albicans (clinical samples)Tween 20>3.00%NCR[75]

Rosa gallica (rose)ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 201.00–2.00%NCR[237]

Rosmarinus officinalis (rosemary) MICC. albicans (ATCC 10231)Tween 800.25% v/v1,8-Cineole (27.23%), -pinene (19.43%), camphor (14.26%), camphene (11.52%)[169]
0.10% v/v1,8-Cineole (26.54%), -pinene (20.14%), camphene (11.38%), camphor (12.88%)[170]
C. albicans (MTCC 1637)n.m.5.50 mg/mLNCR [171]
C. albicans (10 antifungal-resistant isolates)2.75–5.50 mg/mL
C. albicans (ATCC 10231)Acetone5.70 mg/mL1,8-Cineole (41.40%), -pinene (13.30%), camphor (12.40%)[140]
2.00 mg/mL1,8-Cineole (48.00%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 201.00%NCR[237]

Salvia eremophila (sage)MICC. albicans (ATCC 10231)10% DMSO13.00 μg/mLBorneol (21.83%), -pinene (18.80%), bornyl acetate (18.68%)[174]
Salvia officinalis (sage)ADM90Tween 800.50% v/vNCR[236]

Salvia ringens (sage)MICC. albicansn.m.0.75 mg/mL-Pinene (12.85%), 1,8-cineole (46.42%)[177]

Salvia rosifolia (sage) (3 samples)MICC. albicans20% DMSO500.00 μg/mL-Pinene (15.70–34.80%), 1,8-cineole (16.60–25.10%), -pinene (6.70–13.50%)[178]

Salvia sclarea (clary sage) MICC. albicans (13 clinical isolates and 1 reference strain ATCC 10231)1% DMSO128.00–256.00 μg/mLLinalyl acetate (56.88%), linalool (20.75%)[257]
C. albicans (ATCC 10231)Acetone0.88 mg/mLLinalyl acetate (72.90%), linalool (11.90%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 202.00%NCR[237]

Santalum album (sandalwood)ADM90C. albicans (ATCC 10231)Tween 800.06% v/vNCR[236]
MICAcetone2.00 mg/mL-Santalol (32.10%)[99]

Santolina chamaecyparissus (santolina)MICC. albicans (CBS 562 and 4 clinical isolates)n.m.0.25–>1.00 mg/mLNCR[240]

Styrax benzoin (benzoin)MICC. albicans (ATCC 10231)Acetone2.00 mg/mLCinnamyl alcohol (44.80%), benzene propanol (21.70%)[99]

Syzygium aromaticum (clove)ADM90C. albicans (ATCC 10231)Tween 800.12% v/vNCR[236]
MICC. albicans (ATCC 10231)Tween 800.13% v/vEugenol (68.52%), β-caryophyllene (19.00%), 2-methoxy-4-[2-propenyl]phenol acetate (10.15%)[169]
DMSO≤1.00 μg/mLEugenol (84.07%), isoeugenol (10.39%)[118]
MACC. albicans (ATCC 10231)DMSO0.64 μg/mLEugenol (85.30%) [258]
C. albicans (clinical isolate D5)
C. albicans (clinical isolate D1)
MICC. albicans (ATCC 10231)Acetone0.50 mg/mLEugenol (82.20%), eugenol acetate (13.20%)[99]
ADMC. albicans (ATCC 10231 and 3 clinical isolates)Tween 200.12%NCR[237]

Tagetes minuta (Mexican marigold)MIC90C. albicans (ATCC 10231)n.m.115.00 μg/mLDihydrotagetone (33.90%), -ocimene (19.90%), tagetone (16.10%)[159]
Tagetes patula (French marigold)MICAcetone2.00 mg/mL( )--Ocimene (41.30%), -tagetone (11.20%), verbenone (10.90%)[99]

Thymus broussonetii (thyme)MACC. albicans (CCMM L4)n.m.0.25 mg/mLThymol (39.64%), carvacrol (21.31%), borneol (20.13%)[259]

Thymus capitatus (thyme)MICC. albicans (ATCC 10231)Tween 80450.00 μg/mL-Cymene (26.40%), thymol (29.30%), carvacrol (10.80%) [181]
Thymus capitatus (thyme), commercial-Pinene (25.20%), linalool (10.30%), thymol (46.10%)

Thymus herba-barona (thyme)MACC. albicans (ATCC 10231)2% DMSO0.32 μL/mLCarvacrol (54.00%), thymol (30.20%)[246]

Thymus herba-barona (thyme), Limbara MICC. albicans (ATCC 10231)Tween 80450.00 μg/mL-Cymene (27.60%), thymol (50.30%) [181]
Thymus herba-barona (thyme), Gennargentu225.00 μg/mLThymol (46.90%), carvacrol (20.60%)
Thymus magnus (thyme)C. albicans (KCCM 11282)Ethanol and Tween 800.39 mg/mLThymol (39.80%)[260]

Thymus maroccanus (thyme)MACC. albicans (CCMM L4)n.m.0.25 mg/mLCarvacrol (89.15%)[259]
Thymus mastichina subsp. mastichina (thyme)C. albicans (ATCC 10231, H37, M1)n.m.1.25–2.50 μL/mL1,8-Cineole (67.40%)[261]

Thymus quinquecostatus (thyme)MICC. albicans (KCCM 11282)Ethanol and Tween 800.39 mg/mLThymol (41.70%), -terpinene (16.00%)[260]

Thymus schimperi (thyme)ADMC. albicansDMSO0.16 μL/mLNCR[232]

Thymus vulgaris (thyme)MICC. albicans n.m.4.00 μg/μLThymol (47.90%)[253]
MACC. albicans (ATCC 10231, H37, M1)0.16–0.32 μL/mLCarvacrol (70.30%), -cymene (11.70%)[261]
MICC. albicans (ATCC 10231)Acetone2.40 mg/mLThymol (47.20%), -cymene (22.10%)[140]
1.00 mg/mL-Cymene (39.90%), thymol (20.70%)[99]

Thymus x viciosoi (thyme) MACC. albicans (clinical isolates M1, D5), C. albicans (ATCC 10231)1% DMSO0.04–0.64 μL/mLCarvacrol (30.00%), thymol (18.00%), -cymene (19.00%)[262]
Thymus zygis subsp. sylvestris (thyme)C. albicans (ATCC 10231)2% DMSO0.32–1.25 μL/mL -Cymene (11.00–17.00%), γ-terpinene (3.80–11.50%), linalool (3.50–30.00%), geraniol (0.10–19.80%), thymol (5.20–23.80%), carvacrol (1.30–25.00%), geranyl acetate (0.50–20.80%)[263]
Thymus zygis subsp. zygis (thyme)C. albicans (ATCC 10231, H37, M1)n.m.NIThymol (39.60%), -cymene (21.20%)[261]

Vetiveria zizanioides/Andropogon muricatus (vetiver)ADMC. albicans (clinical samples)Tween 20NINCR[75]
MICC. albicans (ATCC 10231)Acetone1.75 mg/mLZizanol (13.60%), -vetirenene (7.20%)[99]

Zingiber officinalis (ginger) ADMC. albicans (clinical samples) Tween 20 3.00% NCR[75]
C. albicans (ATCC 10231 and 3 clinical isolates)[237]

name (common name), part of plant (if applicable).
: microdilution method; MAC: macrodilution method; ADM: agar dilution method, CTA: contact time assay.
Type Culture Collection, Rockville, USA (ATCC); Colección Espanõla de Cultivos Tipo (CECT); collection of microorganisms of the Department of Microbiology (MFBF); culture collection of antibiotics-resistant microbes (CCRM); Eskişehir Osmangazi University, Faculty of Medicine, clinical isolate (OGU); Laboratorio de Microbiología, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina (LM); Microbial Type Culture Collection (MTCC); Mycology Laboratory (LM); National Center of Industrial Microorganisms (NCIM); National Collection of Type Cultures, London, Great Britain (NCTC); Spanish Collection of Type Cultures (STCC).
concentration was not included; n.m.: not mentioned.
: no inhibition.
: no composition results reported.

Cymbopogon citratus, C. martinii, L. nobilis, M. piperita, P. graveolens, Santolina chamaecyparissus (santolina), and Thymus spp. are essential oils recommended in the aromatherapeutic literature for the treatment of fungal infections that have in vitro evidence confirming the effectiveness as antifungals. Cananga odorata (ylang-ylang), Cinnamomum cassia (cinnamon), C. zeylanicum, Coriandrum sativum (coriander), Cymbopogon nardus (citronella), Matricaria chamomilla (German chamomile), and S. benzoin also displayed in vitro noteworthy activity; however, these are interestingly not recommended in the aromatherapeutic literature.

In an in vivo study, L. angustifolia was found to effectively inhibit growth of C. albicans isolated from 20 patients, which was comparative to the inhibition observed by clotrimazole [272].

4.1.6. Fungal Infections: Dermatophytes

Infection with these organisms results in dermatophytosis, which affects the skin, nails, or hair [230, 273, 274]. There is a 10–20% risk of a person acquiring a dermatophyte infection [29], and although the symptoms do not necessarily pose a threat, the treatment is costly and onerous due to resistance and side effects [29]. Essential oils present an excellent option for treating superficial human fungal infections, especially when one is confronted with the effective antifungal results found in previous studies (Table 8). This is encouraging considering the difficulty and challenges faced in treating these infections.

Essential Species Main