Retrospective study of photopatch testing in a Chinese population during a 7-year period

Photoallergic contact dermatitis (PACD) is of importance in a proportion of photodermatoses and can be evaluated through photopatch testing (PPT).

The objectives of this study were to evaluate the results of PPT and investigate the prevalence of PACD reactions to different photoallergens in Chinese patients at the Department of Dermatology of Huashan Hospital Fudan University during a 7-year period.

A retrospective PPT study was conducted. During the 7 years, 4957 patients attending for investigation of suspected photodermatoses were tested according to the European consensus methodology with up to 14 allergens prepared according to Chinese National Standards. The reactions were scored using the International Contact Dermatitis Research Group visual scoring system.

A total of 3472 PACD reactions in 2454 subjects (49.5%) were recorded. The most common agents were chlorpromazine (44.3%), followed by para-aminobenzoic acid (14.7%), thimerosal (8.9%), and sulfanilamide (6.9%). Allergic contact dermatitis reactions comprised 409 reactions in 399 subjects (8%). Photoinhibition and photoaugmentation of allergic contact dermatitis compromised 3810 reactions in 2412 subjects and 11 reactions in 11 subjects, respectively. Irritant reactions (1928 reactions) were seen in 1140 subjects.

The most predominant photoallergens in our region were chlorpromazine, para-aminobenzoic acid, thimerosal, and sulfanilamide, which likely reflected the particular exposures of this Chinese population.