2017 Volume 11 Issue 2 Pages 103-109
Many cases of contact dermatitis due to isothiazolinone preservatives are reported in Japan. Among the well-known cases reported are dermatitis induced by cooling gel products containing 2-n-octyl-4-isothiazoline-3-one (OIT) , and allergic contact dermatitis caused by 2-methyl-4-isohiazolin-3-one (MI) and 5-chloro-2-methyl-4-isothiazolin-3-one (CMI) in cosmetics, paint, adhesives, and toiletry products.
Over a period of 5 years, we patch-tested a total of 832 patients using the Japanese Standard Allergens (JSA) in our department, and we also examined other allergens required by the Japanese Society for Contact Dermatitis. In the past 2 years, we were able to patch-test a total of 85 patients for other allergens containing MI, MI/CMI, Formaldehyde, and other substances. This paper aims to suggest an optimum concentration of MI and MI/CMI (Kathon CG) for patch-testing. Also, we compared the positive ratios for JSA in the group of atopic dermatitis (AD) patients with the group of contact dermatitis (CD) patients.
For MI/CMI, the positive rates were 3.5% (0.02% aq) and 2.3% (0.01% aq) .For MI, the positive rate was 4.6% at a concentration of 0.2%. Since the difference in positive ratio between 0.02%MI/CMI and 0.01%MI/CMI was not very large, we believe that optimum concentration of CMI should be 0.02%, in order to detect any weak sensitivity to the substance. We also believe that 0.2% concentration of MI is an appropriate concentration that should also work for JSA.
In JSA patch-testing, the positive ratio of AD patients (5.9%) was higher than for CD patients (3.8%) for paraben mix. For CMI/MI (Kathon CG) , the positive ratio of CD patients (2.3%) was higher than AD patients (1.2%) .
It appears that the results of the positive ratio of some allergens depend on patient's allergic history.
