CUTANEOUS PHOTOSENSITIVITY DISEASES INDUCED BY EXOGENOUS AGENTS

Cutaneous photosensitivity diseases may be idiopathic, produced by end ogenous photosensitizers, or associated with exogenous photosensitizer s. Those caused by exogenous agents include phototoxicity, photoallerg y, and the exacerbation or induction of systemic disorders in which ph otosensitivity is a prominent clinical manifestation. Phototoxic disor ders have a high incidence, whereas photoallergic reactions are much l ess frequent. The action spectra for most phototoxins and photoallerge ns lie in the WA range. Phototoxic and photoallergic reactions can be distinguished on the basis of pathogenesis, clinical characteristics, diagnosis, and management. Drugs capable of causing phototoxic reactio ns include psoralens, porphyrins, coal tar, antibiotics, and nonsteroi dal antiinflammatory agents. Drugs capable of causing photoallergic re actions include topical antimicrobial agents, fragrances, sunscreens, nonsteroidal antiinflammatory agents, plants, and psychiatric medicati ons. Drug-induced systemic diseases in which photosensitivity is a pro minent component include drug-induced lupus erythematosus, porphyria, and pellagra.