ABSTRACT
Drug-induced skin photosensitivity is a well-documented phenomenon. Exogenous chemicals and drugs may cause photosensitivity by two main mechanisms: phototoxicity and photoallergy. Both processes occur as a result of an offending exogenous agent combined with light exposure. Multiple chemicals, such as psoralens, fl uorescein dye, some thiazide diuretics, and some fl uoroquinolones are able to produce both types of cutaneous reactions. It may be diffi cult to distinguish between these entities, however, they are pathophysiologically distinct processes.
