Allergic contact dermatitis from methyldibromoglutaronitrile

Background. Arriving at a diagnosis of allergic contact dermatitis is a multistep procedure including the establishing of contact allergy, demonstration of current exposure to the sensitizer, and assessment of clinical relevance. Sometimes, these steps are easy to get through; at other times, there may be problems with every step. Objective: To demonstrate the possible difficulties and pitfalls in establishing the presence of contact allergy and diagnosing allergic contact dermatitis from exposure to the preservative methyldibromoglutaronitrile (MDBGN). Methods: Simultaneous patch-testing with petrolatum preparations of MDBGN at various concentrations, use testing, and chemical analysis with high-performance liquid chromatography (HPLC). Results: Contact allergy to MDBGN was established in two cases, with MDBGN in petrolatum at 0.5%. Results of HPLC investigation of moisturizers used by the patients and yielding positive results on patch and use tests disagreed with the information about preservatives on the labels of the moisturizers and with the Material Safety Data Sheets (MSDSs). Conclusions: Patch testing with MDBGN in petrolatum at a concentration of less than 0.5% may fail to diagnose a clinically relevant contact allergy. The information on labels of products, on MSDSs, and from manufacturers may not be reliable, which indicates the need for chemical analyses.