LAUSR

Contact allergy to isothiazolinones is frequent, especially to methylisothiazolinone (MI) alone and combined with methylchloroisothiazolinone (MCI/MI). While the incidence of MI allergy is decreasing, it remains clinically relevant, in part due to occupational exposures. A spot test kit for detection of isothiazolinones in industrial water systems is commercially available (Tintometer Group) (http://www. lovibondwater.com/product/isothiazoline.aspx). This spot test was recently used to identify a clinically relevant but undeclared exposure to MI in the raw material of a facial gel mask, suggesting the clinical value of the test. The manufacturer states that the test can detect isothiazolinones down to the level of 0.75 ppm; however, it is unclear whether this applies to the most relevant isothiazolinones responsible for contact allergy. We examined the sensitivity of this spot test against 3 common isothiazolinones, and report two clinical cases where application of the test helped us identifyMI andMCI/MI sources in allergic patients.