Photopatch testing

Abstract

Photopatch testing is a procedure that combines patch testing with UV irradiation. It is indicated to primarily study photoallergic contact dermatitis, but it can also contribute to establish a correct diagnosis of any exposed site dermatitis or systemic photosensitivity. Photoallergens suffer temporal and regional variations. The most frequent are UV filters and topical drugs, particularly non-steroidal anti-inflammatory drugs (NSAIDs), but apart from these, photoallergens series should include regionally prevalent photoallergens, and doctors must be alert to the possibility of involvement of imported historical photosensitizers. The method is standardized, with the application of two sets of allergens and irradiation at D1 or D2 with 5 J/cm2 of UVA. Result interpretation is essential as reactions can be contact allergy, photoallergy, photo-augmented allergic contact dermatitis or non-specific phototoxic or irritant reactions. © 2011 Springer-Verlag Berlin Heidelberg.