Contact dermatitis from methylisothiazolinone in a paint factory

Introduction of new potential contact-sensitizing chemicals have in the past led to epidemics of contact dermatitis. A new preservative containing only methylisothiazolinone (MI) and not methylchloroisothiazolinone (MCI) has recently been introduced in the European Union for use in products, such as paint, glue and cosmetics. The objective of this article is to describe a factory outbreak of contact allergy to MI and MCI preservatives. This factory outbreak describes allergic contact dermatitis towards MI in 4 patients of 14 persons working at a paint manufacturer. Patch test results from all patients showed positive reactions for MI and MCI/MI. The reactions were stronger for MI than MCI/MI indicating a primary sensitization to MI. The combination of MCI/MI remains widely used, and therefore various patterns of exposure and sensitization could be seen in the future. Our data show that MI holds a potential for eliciting and propably inducing contact allergy in humans. Whether this preservative is safe to use in cosmetics where billions of consumers are exposed needs a care full monitoring.