Noneczematous Contact Dermatitis

Table 4

Differential diagnosis between true erythema multiforme (EM) and erythema multiforme-like contact dermatitis.

Criteria	EM	EM-like contact dermatitis
Etiology	Viruses, bacteria, systemic drugs	Various topical chemicals
Clinical features	Erythematoedematous lesions with cockade appearance, sometimes bullous, with acral localization (face, hands, forearms, thighs)	Polymorphic lesions located peripherally to the contact site with the sensitizing agent
Fever	Often present	Absent
Mucosal involvement	Frequent	Rare
Histology	Epidermis: basal cells necrosis, subepidermal vesicobullae; Dermis: edema, capillary vasodilation, vasculitis signs	Epidermis: spongiosis; Dermis: edema, lymphohistiocytic infiltrate
Pathogenesis	Immunocomplexes	Type IV hypersensitivity
Patch tests	Negative	Positive
Course	Self-limited in 3 weeks	Favorable after allergen withdraw