Should methyldibromo glutaronitrile continue to be used in the European baseline Series? A REIDAC 1 national cross-sectional study.

Background Methyldibromo glutaronitrile (MDBGN) was one of the most frequent and relevant allergens found in patch testing at the beginning of the 2000's. In 2008 this preservative was banned from cosmetics in Europe and ever since the prevalence of contact allergy to MDBGN progressively decreased. Despite that gradual decline, it is still patch-tested in most baseline series. This study assesses the frequency of MDBGN sensitization, epidemiological characteristics of allergic patients as well as the relevance of positive patch tests in a nationwide Spanish registry (REIDAC). Patients and methods We evaluated consecutively patch tested patients in all participating centres. Using these data, we calculated the proportion of patients with positive patch tests to MDBGN from June 2018 until June 2020 and evaluated the relevance of positive patch tests to MDGN. Results 114 out of 5072 (2.24 %) tested patients were sensitized to MDBGN. Clinical current relevance was confirmed in only one case. Conclusion Although the frequency of contact allergy to MDBGN remains high, no clinical significance was found in most of these patients (5072 tests needed to obtain one relevant positive result). The clinical usefulness of this allergen seems weak and its continued inclusion in the European baseline series is questionable. This article is protected by copyright. All rights reserved.