Background: Cosmetic cleansers are most widely used to remove makeup and sometimes cause allergic or irritation contact dermatitis. We can patch test soaps or shampoos as 2% concentration, but cleansers have been not determined for the concentration by patch test yet. Objective: The objectives of this study were to determine the concentration of cosmetic cleansers for patch test. Methods: The skin responses to patch testing with variable cleansers in different concentrations were measured by visual scoring, spectrometer, evaporimeter and comeometer. Results: The results of the studies were summarized as follows; l. The cream type and lotion type cleansers showed no skin responses. 2. The skin response of foam type cleansers showed that the one had statistical significance between 2% and 5%, and the other had 5% and 10% concentration. 3. The skin response of gel type cleansers showed statistical significance between 5% and 10% concentration. 4. Through correlation analysis, we found that the evaluation of the evaporimeter or comeometer was not related to the visual measurement. Conclusions: We suggest that cosmetic cleansers of water, lotion and cream type can be tested as is (100%), and foam type cleansers with 2%, and gel type should be tested with 5% concentration. (Korean J Dermatol 2001;39 (7) : 755~760)