The Photopatch Test

The photopatch test serves as a tool to diagnose photosensitivity due to phototoxic or photoallergic substances. Photoallergic reactions require sensitization of the patient before the reaction can be elicited. Phototoxic reactions already occur at first contact with the photosensitizer. Phototoxic reactions are defined as photochemical processes; however, the individual susceptibility varies greatly among patients. The relevance of positive test reactions only can be evaluated concerning the clinical features and history of the patients.