Allergic contact dermatitis and photosensitivity to methylisothiazolinone and methylchloroisothiazolinone/methylisothiazolinone: Portrait of an epidemic in Brazil

Methylisothiazolinone (MI) is a preservative associated with an epidemic of allergic contact dermatitis worldwide, mainly owing to its use in cosmetics, where it is found alone or combined with methylchloroisothiazolinone (MCI/MI, eg. Kathon CG). There are very few studies on sensitization to MI in Brazil, although cases of an unusual pattern of photoeczema associated with MCI/MI allergy have been reported in the country. The Brazilian baseline patch test series (FDA Allergenic, Rio de Janeiro, Brazil) does not contain MI and since its creation, MCI/MI 0.5% pet. has been tested–a concentration well above the 0.02% or 0.01% used in sets from other countries and in a different vehicle. This study aimed to evaluate the profile of MI sensitization in Brazil, the efficacy of MCI/MI 0.5% pet. in the detection of sensitized patients, and the occurrence of photoeczema to isothiazolinones.