Octylisothiazolinone, an additional cause of allergic contact dermatitis caused by leather: case series and potential implications for the study of cross-reactivity with methylisothiazolinone.

BACKGROUND: Octylisothiazolinone (OIT) is used as an antifungal agent by the leather industry. OBJECTIVES: To show sensitization to OIT from leather, and to highlight the potential implications when cross-reactivity between OIT and methylisothiazolinone (MI) is studied. METHODS: Two patients with allergic contact dermatitis caused by a leather belt and shoes, respectively, were patch tested with methylchloroisothiazolinone (MCI)/MI, MI, MCI, OIT, and benzisothiazolinone (BIT). High-performance liquid chromatography with ultraviolet detection (HPLC-UV) was used to detect isothiazolinone derivatives in leather goods. Additionally, files of OIT-sensitized patients, observed at the KU Leuven department during the period 1990-2015, were retrospectively analysed. RESULTS: Both patients had been primarily sensitized to OIT, but the diagnosis in one of them could be achieved only when a higher patch test concentration of OIT (1000 ppm pet.) was used. HPLC-UV confirmed the presence of OIT in their leather goods. Non-relevant sensitization to MI was noted in both cases. Four additional cases of OIT sensitization from leather could be retrieved from the KU Leuven database. CONCLUSIONS: Non-occupational sensitization to OIT from leather may occur. Patch test concentrations of >250 ppm pet. may be necessary for diagnosis, and to show cross-reactivity with MI. Safer use limits for OIT in the leather industry may be needed.