Successful photopatch testing with ketoprofen using one-hour occlusion.

The standard procedure for photopatch testing includes 24-h occlusion of the allergen, followed by irradiation at 5 J/cm2 ultraviolet A (UVA). Due to the timing, a separate visit to the clinic is needed for UV irradiation. The aim of this study was to determine whether a reduction in occlusion time from 24 h to 1 h, in order to simplify the testing procedure, influences test results when photopatch testing with ketoprofen. A total of 22 patients with a known or suspected photo-allergy to ketoprofen were simultaneously photopatch-tested with ketoprofen using both 1 h and 24 h occlusion. One side of the patient's back was irradiated with 5 J/cm2 UVA, and the other side was covered. Measurements were made after 3 days on both irradiated and non-irradiated sides. A total of 20 controls were photopatch-tested with ketoprofen using 1 h occlusion. All of the patients showed positive reactions on the irradiated side. No positive reactions were observed on the non-irradiated side. All controls were negative. In conclusion, 1 h occlusion time is sufficient to establish photo-contact allergy to ketoprofen. No adjustments in UVA or ketoprofen dose were needed. Limiting occlusion time to 1 h could simplify the photopatch test procedure by eliminating one visit to the clinic. These results apply only to ketoprofen; further studies are needed to determine whether a similar approach can be used with other components of photopatch test series.