Methyldibromoglutaronitrile in leave-on products elicits contact allergy at low concentration

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.

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.

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.

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.

Even 50 p.p.m. cannot be regarded as a safe concentration for use and the prohibition of MDBGN is scientifically well founded.