Objectives To conduct PPT using a group of sunscreen chemicals, defined indications and a standardized methodology including interpretation and relevance of reactions in patients attending for investigation at 17 centres across the U.K., Ireland and the Netherlands.
Methods Patients (n = 1155) who fulfilled the inclusion criteria were investigated with PPT using sunscreen chemicals in addition to suspected topical products. Readings were taken at 24, 48 and 72 h following standardized ultraviolet A irradiation (5 J cm-2). The clinical relevance of any reaction was recorded.
Results Of the 1155, 130 had allergic reactions (11·3%). Of these, 51 had photoallergy (PA) (4·4%), 64 had contact allergy (CA) (5·5%), and 15 patients had combined PA and CA (1·3%). Multiple PA was seen in some. The most common photoallergen was benzophenone-3 (27 reactions; 21%). Most reactions (60%) were clinically relevant. The most common indication for testing in patients found to have PA was a history of reacting to a sunscreen (41%). The other 59% had an exposed-site dermatitis/skin problem or a photodermatosis. Some centres (n = 8) performed readings after the standard 48-h reading, and an extra 32 PA and 22 CA reactions were detected, which were not evident at 48 h. A new photoallergen (octyl triazone) was detected in two patients.
Conclusions Sunscreen PA and CA are probably equally uncommon. Most reactions, of both reaction types, were relevant clinically. A large proportion of patients (59%) found to have PA was unaware of reacting to a sunscreen chemical, suggesting that PA should be considered as an explanation in any exposed-site dermatitis. Although this study focused on reactions at 48 h postirradiation, readings performed up to 96 h, while inconvenient, add value by detecting additional relevant responses. A previously unknown photoallergen was found, highlighting the need for awareness of novel photoallergens in the marketplace. A standardized PPT method not only encourages more use of this investigation, but also facilitates comparison of results between centres and so will improve our understanding of PA.
- Ultraviolet Rays
- Sex Factors
- Patch Tests
- Child, Preschool
- Aged, 80 and over
- Dermatitis, Photoallergic
- Sunscreening Agents
- Middle Aged