Background: The rapidly increasing level of contact allergy to methyldibromoglutaronitrile (MDBGN) in Europe is of concern. In April 2003, the EU Commission prohibited the use of MDBGN in leave-on cosmetic products, such as creams and lotions, until a level of safe use can be defined. Industry risk assessment has indicated that such a safe level could be 50-100 p.p.m.
Objectives: To determine whether 50 p.p.m. or 100 p.p.m. could be tolerated by MDBGN-sensitized individuals, and to evaluate if the risk for elicitation of MDBGN allergy is higher for a leave-on product with a high lipid content than for a product with a low lipid content.
Methods: Eighteen volunteers with contact allergy to MDBGN and 10 healthy controls were exposed to repeated open application tests (ROATs) with two moisturizers with a high and a low lipid content, respectively, both containing MDBGN at a concentration of 50 p.p.m. The ROATs were performed on the left and the right side of the neck for 14 days, or until a positive reaction was seen. If a positive reaction did not develop within the first 14 days, two analogous moisturizers containing 100 p.p.m. MDBGN were applied for a further 14 days. Clinical assessments were done on days 2, 3, 7, 14, 21 and 28 or when a reaction developed.
Results: Eleven of 18 (61%) subjects developed dermatitis on the test area, of whom 10 developed a positive reaction to the 50 p.p.m. moisturizer, seven having a positive reaction on day 2 or 3. Reactions to the low-lipid moisturizer were the more frequent. All participants used more of the low-lipid moisturizer than the high-lipid moisturizer. The controls all had negative ROATs.
Conclusions: Even 50 p.p.m. cannot be regarded as a safe concentration for use and the prohibition of MDBGN is scientifically well founded.