Intended for healthcare professionals

Photocontact allergy and photopatch testing

Sally H Ibbotson
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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Dermatology in practice was previously supported by Wyeth from 2008 to 2010, by Wyeth and Serono in 2007, by Wyeth and Shire from 2005 to 2006, by Medlock Medical in 2004 and by SSL International from 2001 to 2003.

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