Analysis of isothiazolinones and other preservatives in leather, synthetic leather, and textile products available in Japan.

Isothiazolinone-based preservatives have recently emerged as notable contributors to non-occupational allergic contact dermatitis (ACD). However, comprehensive data on their prevalence and concentrations in consumer products with prolonged skin contact remain limited. This study aimed to quantify 12 preservatives, including various isothiazolinones, in leather, synthetic leather, and textile products available in Japan. Notably, 2-n-octyl-4-isothiazolin-3-one (OIT), 2-methyl-4-isothiazolin-3-one (MI), and 1,2-benzisothiazolin-3-one were frequently detected in leather and synthetic leather, with some of these products containing relatively high concentrations of OIT (up to 150 µg/g). These levels were comparable to those observed in cases of ACD associated with OIT-containing leather. Other preservatives, such as 4-chloro-3-methylphenol, 2-(thiocyanomethylthio)benzothiazole, and o-phenylphenol, were also found in several products. In textiles, only low concentrations of MI, triclosan, and triclocarban were detected. Although there has been no significant increase in ACD cases related to these preservatives in Japan to date, continuous monitoring of their usage and associated clinical outcomes is essential. The findings of this study highlight the importance of monitoring the preservatives used in products that come into direct and prolonged contact with the skin.