150 patients with light sensitivity of unknown aetiology were photo patch tested at the 2nd Department of Dermatology University of Vienna. 22 patients showed photoallergy. The identified photoallergens were mostly halogenated salicylanilides and other phenolic compounds. These substances are used as antimicrobials in soaps and cosmetics and as antimycotics in dermatological preparations. Four of the patients showed allergic contact photosensitivity to chlorpromazine. In two patients a new photoallergen has, perhaps, been discovered, namely a derivative of phthalic acid which is employed as fungicidal pesticide. The problems and consequences of photoallergy are discussed.