Methyldibromoglutaronitrile (Euxyl K 400): an important "new" allergen in cosmetics.

Euxyl K 400 is a preservative system for cosmetics and toiletries that contains phenoxyethanol and methyldibromoglutaronitrile in a 4:1 ratio. In The Netherlands, Italy, and Germany, the prevalence of allergy to Euxyl K 400 has risen in the past 4 years and is currently 2% to 4% in patients suspected of having contact dermatitis. The allergenic ingredient is nearly always methyldibromoglutaronitrile. Causative products include both stay-on and rinse-off cosmetics and moistened toilet tissue. Because the causative products usually give false-negative reactions, the allergen, methyldibromoglutaronitrile, should be tested in all patients suspected of having cosmetic dermatitis and in those with perianal dermatitis. We suggest a test concentration of 0.3% to 0.5% in petrolatum.