Repeated open application tests with methyldibromoglutaronitrile in dermatitis patients with and without hypersensitivity to methyldibromoglutaronitrile

Background: Contact allergy to and allergic contact dermatitis from methyldibromoglutaronitrile (MDBGN) have been frequently reported since the 1990s. Objective: This study was initiated to help determine the optimal test preparation for MDBGN and to help determine the clinical relevance of such a contact allergy. Method. In 38 patients with positive (32 patients) or doubtful (6 patients) patch-test reactions to at least one of four test preparations of MDBGN in petrolatum at 1.0%, 0.5%, 0.3%, and 0.1% (all weight per weight [w/w]), a repeated open application test (ROAT) with moisturizers with and without MDBGN at 0.03% w/w was conducted on patients' upper arms for a maximum of 4 weeks. Seven patients not hypersensitive to MDBGN served as controls and went through the same procedure. Results: Nineteen (59.4%) of the 32 MDBGN-allergic patients developed a positive ROAT result on the arm on which the moisturizer containing MDBGN was applied whereas no patients with doubtful or negative reactions to MDBGN reacted (p = .002). A statistically significant association was found between the patch-test reactivity and the outcome of the ROAT (p < .001). Conclusion: Patch testing with MDBGN at 0.3% and 0.1% will miss clinically relevant patch-test reactions to MDBGN.