Occupational Allergic Contact Dermatitis From Over‐Ear Headphones: Chemical Analysis Reveals Octylisothiazolinone and Other Potential Skin Sensitizers

BACKGROUND: Over-ear headphones are a growing source of allergic contact dermatitis (ACD). Identifying well-known and new culprit sensitizers in such products is challenging because of a lack of labelling and limited cooperation from manufacturers. OBJECTIVES: To report potential skin sensitizers in occupationally-used headphones from patients attending an occupational allergy clinic. PATIENTS AND METHODS: The over-ear headphones from two octylisothiazolinone (OIT)-allergic patients with ear ACD were chemically analysed using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). RESULTS: UPLC-MS/MS confirmed the presence of OIT, but also other biocides (1,2-benzisothiazolin-3-one, cetylpyridinium chloride), rubber accelerators (zinc dibenzyldithiocarbamate, 1,3 diphenyl guanidine, 1,3 di-O-tolyguanidine, tetramethylthiuram disulfide, tetraethylthiuram disulfide), acrylates (isobornyl acrylate [IBOA]), plasticizers (triphenyl phosphate [TPP], tricresyl phosphate), oxidizers (benzoylperoxide) and organic solvent (dimethylformamide [DMF]). CONCLUSIONS: Over-ear headphones may contain reproductive toxicant such as DMF, as well as several sensitizers, including TPP, OIT and IBOA. Under the EU REACH Regulation, the use of DMF is restricted, TPP is listed as a Substance of Very High Concern, whereas OIT and IBOA are not subject to specific restriction. Across both occupational and non-occupational settings, the use of over-ear headphones may cause contact dermatitis due to exposure to various chemical substances. Our findings may serve to explain these and future cases.