Photobiomodulation (PBM), earlier recognized as low-level laser therapy (LLLT), was discovered more than 50 years ago. For much of this time, several biological properties have been attributed to LLLT. However, non-coherent light-emitting diodes (LEDs) have been considered to have similar effects as LLLT, with the added advantage of being less expensive and having fewer safety concerns. Data generated by basic science researchers and clinical practitioners have shown biological processes and disease ailments that have responded well to PBM.

Many of the biological effects of PBM are attributed to photons absorption by chromophores located inside mitochondria to boost cellular metabolic activity. Moreover, changes in the levels of reactive oxygen species (ROS) have often been observed when applying light. This is important because, after photon absorption, numerous signalling pathways can be activated via ROS to increase expression of genes related to protein synthesis, cell migration and proliferation, inflammation, apoptosis, and antioxidant enzymes.

This Special Issue focuses on PBM modulating oxidative stress. This Issue will bring together articles that address the role of PBM in modulating oxidative stress in broad physiological and pathological conditions including but not limited to the alleviation of pain or inflammation, immunomodulation, promotion of wound healing, hair growth, cancer treatment, improvement of physical performance and blood circulation, and tissue regeneration. We welcome manuscripts that clarify mechanisms of action and signalling pathways of PBM linked to redox balance and that may be involved in physiological changes and the improvement of clinical outcomes. Original research and review articles are welcome.

Potential topics include but are not limited to the following:

• Molecular and cellular mechanisms of oxidative stress associated with PBM: impact on health and disease
• PBM strategies to prevent/treat cellular damage underlying oxidative stress
• Optimizing irradiation parameters to enhance the protective and regenerative effects of PBM mediated by oxidative stress
• Recent discoveries in animal models to understand the role of LLLT and LEDs in human disorders connected to excessive oxidative stress
• Implications of different irradiation parameters in the redox balance and antioxidant defence
• Impact of PBM combined with pharmacological and non-pharmacological therapies to improve oxidative stress in multiple tissue disorders