Trends in Benzisothiazolinone Sensitization: A Retrospective Analysis From 2010 to 2022, in a Tertiary Belgian Hospital

Background Benzisothiazolinone is a preservative responsible for allergic contact dermatitis, with occupational exposure being a common source of sensitisation. Objectives To investigate the prevalence of positive patch test reactions to benzisothiazolinone (BIT) in Belgium, between January 2010 and December 2022, and to assess co‐sensitisations to other isothiazolinone derivatives in sensitised patients. Methods A retrospective monocentric study of patch test results with benzisothiazolinone (BIT) 0.1% petrolatum observed in patients attending a Belgian tertiary hospital. Prevalence, demographic data, concomitant patch test reactions, and clinical relevance were analysed. Results Overall, 65 of 6128 patients (1.06%) had a positive patch test reaction to benzisothiazolinone, and its sensitisation rate increased from 0.39% in 2010 to 3.72% in 2019 (followed by a decline to 0.71% in 2022). Occupational exposure was relevant in 20% of cases, with painters and metalworkers being the most affected professions. Unexpectedly, 10.8% of BIT‐sensitised patients underwent patch testing due to complications following orthopaedic prosthesis implantation. Conclusions This study confirms a significant rise in BIT sensitisation over time, followed by a recent unexplained decline. Occupational exposure remains a major risk factor, but other environmental sources, including consumer products, such as leather products, should not be overlooked. The BIT sensitisation in orthopaedic prosthesis‐related complications requires further investigation.