RESUMEN
Some types of cosmetic products such as hand soaps and creams are commonly used several times a day, especially in occupational use situations. Little has experimentally been shown of how the daily frequency of the application of an allergen in a product influences the allergic response. This study investigates the allergic responses elicited in presensitized individuals when exposed to a specific amount of allergen applied either in 1 application per day or distributed over 4 applications per day. As model allergen, the cosmetic preservative methyldibromo glutaronitrile (MDBGN) is used. 19 contact allergic individuals and 12 controls participated in a double-blind, randomized use test. To areas on the forearms were applied 2 drops either once daily of a solution containing 0.04% MDBGN or 4 times a day of a solution containing 0.01% MDBGN. 14 of 19 patients developed dermatitis following the application of approximately equal amounts of MDBGN on both arms. Controls were negative. In this experiment, applications of 0.04% MDBGN once daily or 0.01% MDBGN 4 times daily had, in a use test, approximately equal capabilities of provoking allergic contact dermatitis. This adds new knowledge to the risk assessment and regulation of cosmetic allergens. However, these results may be highly allergen dependent, and further studies are needed before more general conclusions can be made.