Photopatch testing: Clinical characteristics, test results, and final diagnoses from the North American Contact Dermatitis Group, 2009–2020

Abstract

AbstractBackgroundPhotoallergic contact dermatitis (PACD) is a delayed hypersensitivity reaction to allergens only in the presence of ultraviolet radiation in sunlight. Photopatch testing (PhotoPT) is necessary to confirm the diagnosis of PACD. There are few published studies of PhotoPT in North America.ObjectiveTo summarise the results of patients photopatch tested by members of the North American Contact Dermatitis Group (NACDG), 2009–2020.MethodsRetrospective analysis of patient characteristics and PhotoPT results to 32 allergens on the NACDG Photopatch Test Series.ResultsMost of the 454 tested patients were female (70.3%), 21–60 years old (66.7%) and White (66.7%). There were a total of 119 positive photopatch tests. Sunscreen agents comprised 88.2% of those, with benzophenones responsible for over half of them. Final diagnoses included PACD in 17.2%, allergic contact dermatitis (ACD) in 44.5%, polymorphous light eruption (PMLE) in 18.9% and chronic actinic dermatitis (CAD) in 9.0% of patients.ConclusionsIn 454 patients with suspected photosensitivity referred for photopatch testing in North America, approximately one‐fifth had PACD. Sunscreen agents, especially benzophenones, were the most common photoallergens. Other common diagnoses included ACD, PMLE and CAD. Photopatch testing is an important tool for differentiating these conditions.