PD08 Photopatch testing and photodiagnostic investigations in a tertiary photodiagnostic service: a 5-year review

Abstract

Photopatch testing and photodiagnostic investigations are important in the assessment of suspected photosensitivity conditions and are typically delivered through tertiary photodiagnostic services. We reviewed patients who had been photopatch tested through such a service from 2020 to 2025, documenting clinical features and photodiagnostic findings, to assess current practices. This retrospective study was conducted with Caldicott Guardian approval (IGTCAL-2025-296). Study data were obtained through review of clinical photodermatology records and an in-house photodiagnostic database. The median age of the 157 patients studied was 46 years (range 3–83), with 121 (77%) female. Most had skin phototype I–III (115 of 126 with data, 91%) and 88 of 157 (56%) were atopic. The majority used sunscreens (95 of 115, 83%). Most (115 of 157, 73%) presented with facial dermatitis and/or swelling, and of those, 68 of 115 (59%) used sunscreen. Photopatch testing identified photocontact allergy in 20 of 157 (13%) and contact allergy in 41 of 157 (26%). Of those with positive photocontact and/or contact allergy (n = 57), 79% were female, and 72% presented with facial dermatitis and/or swelling. Of those who also had standard patch testing, 77 of 98 (79%) had positive results. The most frequent photopatch test photoallergens or allergens were Uvistat® SPF50 (n = 23), Sunsense Sunsensitive® SPF 50+ (n = 21), octocrylene (n = 8), lauryl polyglucose (n = 7) and oxybenzone (n = 3). Abnormal monochromator phototesting occurred in 68 of 151 (45%), with 7 of 133 (5%) patients tested having an abnormal narrowband ultraviolet B minimal erythema dose. Vitamin D insufficiency (< 50 nmol L−1) occurred in 55 of 120 (46%) and elevated IgE (> 100 kU L−1) in 44 of 99 (44%). The median Dermatology Life Quality Index was 12 (range 1–30) (n = 137). While the most prevalent diagnosis was polymorphic light eruption (58 of 157; 37%), a range of diagnoses were reported, including photocontact allergy and other photodermatoses. We wish to highlight the importance of photopatch testing, particularly in female patients with facial dermatitis and/or swelling. The diverse range of diagnoses identified highlights the need for comprehensive assessment through specialized photo­diagnostic services.