Standardization of patch tests in Japan

In order to standardize patch tests in Japan a comparative study of our former method of patch testing with that recommended by the International Contact Dermatitis Research Group (ICDRG) was carried out with the collaboration of dermatologists in the Mid-Japan Dermatological Society. The following differences were observed between the two methods of patch testing: 1. Four out of five ICDRG allergens which were common in Japanese standard allergen series--formaldehyde, potassium dichromate, cobalt chloride and nickel sulfate--showed higher reactivity than those of Japanese allergens. The other allergen, paraphenylenediamine (PPD), showed the same reactivity as Japanese PPD. Cobalt chloride of ICDRG origin showed a particularly higher reactivity than the Japanese one (a=0.05) 2. Higher reactivity was observed at the 48-h reading when aqueous reagents were patch-tested using Torii-Ban, Miniplaster and Leukotest, which are all popular in Japan. This higher reactivity could be attributed to the lint gauze of plasters which are pre-treated with fluorescent whitener. 3. The incidence of reactivity of the ICDRG allergens in Japan was also studied in order to establish a new standard allergen series.