Results of photopatch testing in Rotterdam during a 10-year period

Background Photoallergic contact dermatitis is of importance in a proportion of photodermatoses and can be evaluated through photopatch testing. Objectives To conduct a retrospective evaluation of photopatch tests performed in patients with suspected photodermatoses at the clinic at the University Hospital Rotterdam during a 10-year period. Methods During the first 5% years 44 patients were tested with a standard set of 14 allergens, and during the next 4% years 55 patients were tested with a standard set of 23 allergens. Results Photocontact reactions were found in 9% and 27% of patients in the two periods, respectively. In the second period, positive reactions were mostly produced by sunscreens. The difference in the percentage of positive photopatch tests was probably caused by the difference in composition of the standard set of allergens (more sunscreens in the second period), this being the only alteration in the test procedure. Conclusions The standard set of photoallergens has to be updated periodically. Standardization of the test procedure is needed to compare the test results of different institutions.