Photocontact allergy and photopatch testing
Photocontact allergy is uncommon and considered to be a delayed type IV hypersensitivity reaction, in which a photoactivated chemical acts as an antigen or hapten. Photopatch testing is used to investigate and diagnose photocontact allergy; sunscreen chemicals are the major group of clinically relevant photoallergens. Both sunscreen users with normal sun sensitivity and patients with existing photosensitive diseases may develop photocontact allergy, and this needs to be considered as a differential diagnosis in the presentation of a patient with a photoexposed site dermatitis or with a history of a reaction to a sunscreen.
Dermatology in practice 2002; 10(3): 16–19
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