ABSTRACT
Test procedures designed to identify potentially photosensitizing chemicals evolved in the wake of the photosensitivity outbreak caused by the antimicrobial halogenated salicylanilides in the early 1960s. Photocontact allergy, although relatively uncommon, proved to be particularly troublesome. Test procedures for identifying photocontact allergens have received less attention than methods designed to detect ordinary contact sensitizers. The coumarins, which constitute a large class of synthetic and naturally occurring substances, are potentially strong photosensitizing agents. Absorption of ultraviolet (UV) energy by the sensitizer in the skin is required for both induction and elicitation. Photomaximization test is conducted in humans and is essentially a repeated insult technique that entails an exaggerated exposure to both chemical and UV and follows a design similar to that of the maximization test. It is a useful laboratory procedure for identifying substances that are potentially capable of producing photoallergic contact sensitivity in humans.
