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

Contact allergy to and allergic contact dermatitis from methyldibromoglutaronitrile (MDBGN) have been frequently reported since the 1990s. 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. 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. 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). Patch testing with MDBGN at 0.3% and 0.1% will miss clinically relevant patch-test reactions to MDBGN.