A European multicentre photopatch test study

Background The two most common agent groups currently responsible for photoallergic contact dermatitis (PACD) are organic ultraviolet (UV) absorbers in sunscreens and topical nonsteroidal anti-inflammatory drugs (NSAIDs). However, availability of information on the photoallergenic potential of these agents is scarce. Objectives To obtain current information on the frequency of PACD to 19 organic UV absorbers and five topical NSAIDs, including newer agents, in common usage in Europe. Methods A prospective, multicentre photopatch test study was conducted with 1031 patients attending for investigation of suspected PACD in 30 centres across 12 European countries. Results A total of 346 PACD reactions in 200 (19·4%) subjects occurred. PACD was most commonly caused by the topical NSAIDs, ketoprofen (128 subjects) and etofenamate (59 subjects). Of the organic UV absorbers, octocrylene, benzophenone-3 and butyl methoxydibenzoylmethane most frequently elicited PACD. The 'newer' organic sunscreen absorbers rarely led to PACD. There appeared to be an association between the agents ketoprofen, octocrylene and benzophenone-3, with several subjects developing PACD to two or all three agents concomitantly. Allergic contact dermatitis (ACD) was less commonly observed than PACD, comprising 55 reactions in 47 (5%) subjects. Irritant reactions and photoaugmentation and photoinhibition of ACD occurred infrequently. Conclusions The European multicentre photopatch test study has provided current information on the relative frequency of PACD to common photoallergens. Such data will be of value when deciding on which agents to include in a future European 'baseline' photopatch test series.