Background: Methylisothiazolinone (MI) is used as a preservative in occupational and household products, and cosmetics. It is a part of the preparation of methylchloroisothiazolinone (MCI)/MI, which is patch tested in water in the European baseline series. However, this preparation fails to detect a significant percentage of allergic contact reactions to MI.
Objectives: To investigate whether a separate test preparation with MI should be included in the European baseline series.
Methods: Literature survey.
Results: In consecutively tested dermatitis patients, the contact allergy rate for MI varies between 0.6% and 6%, with a marked increase in recent years. The contact allergy rate for MI alone, not detected with MCI/MI, varies between 0% and 1.6%. Most cases are relevant, as shown by repeated open application test studies, and are mainly related to exposure from cosmetic products.
Conclusions: Owing to the increase in contact allergy to MI not detected with MCI/MI, it is recommended that MI in water at 2000 ppm be included in the European baseline series. With the Finn Chamber(®) (diameter, 8 mm) technique, a volume of 15 µl should be applied, giving a dose of 60 µg/cm(2).
Keywords: European baseline series; MCI/MI; allergic contact dermatitis; contact allergy; dose in µg/cm2; methylisothiazolinone; micropipette; patch test sensitization; preservative.
© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.