Abstract: Objective To study the role of photoallergens and contact allergens in the pathogenesis of chronic actinic dermatitis (CAD). Methods Ba sed on the standard procedures of photopatch test recommended by the British Photodermatology Group (BPG) and the routine procedures of patch test,photopatch and patch tests were performed on 56 patients with CAD,42 patients with polymorp hous light eruption (PLE) and 25 patients with chronic eczema on scalp and face by standard photopatch test series recommended by the International Contact Dermatitis Research Group (ICDRG) and home-made standard series of contact allergens.A set of ten Philips TL20W/09N tubes was used as the source of irradiation. Results In the 56 CAD patients,the positive rates were 46.43%,57.14% and 32.14% for photopatch test,patch test and both tests,respectively,which appea red to be significantly higher than those in the patients with PLE.Positive pa tch reactions were found in 65% of the patients with chronic eczema,which was similar to that of CAD.And the frequency of the positive allergens in chronicec zema was the same as that in CAD,in which fragrance mixture (FM) ranked the first,followed by balsam of Peru (BOP),cobalt chloride,nickel sulphate.In CAD,FM and BOP were the most common allergens and photoallergens,which accounted fo r 44% and 32% of the positive reactions in patch tests,15.38% and 17.95% in photopatch tests,respectively. Conclusions Both photoallergens and contact aller gens may play important roles in the pathogenesis of CAD.Allergens positive in patch tests and photopatch tests and related compounds which can cause cross-reactivity with the above allergens should be avoided by the patients with CAD.

Key words: Patchtests, Dermatitis, photoallergic, Skin tests