[New light on skin photodynamic therapy].

Photodynamic therapy (PDT) relies on the cellular toxicity of an exogenous porphyrin that is activated by light rays. Its specificity depends on its cellular uptake, which is typically high in cells with a high metabolism, such as cancer cells and several microbial pathogens. Both the diffusion of the substrate and the penetration of the light in the tissue limit its efficiency to the first few millimeters of the skin. This explains why this technique is used for the treatment of superficial skin cancers (actinic keratosis and basal cell carcinomas), but also for selected skin inflammatory diseases (psoriasis) or infections (leishmaniosis). However, at the bedside, the limitations of PDT are rather the complexity and the pain associated with the treatment. Herein, we present the new developments, in particular concerning the new light sources, which make PDT a better option for our patients.