Methylisothiazolinone: second 'epidemic' of isothiazolinone sensitization.

Isothiazolinones are used as biocides in a wide variety of products, such as cosmetics, detergents, and industrial products. In the 1980s, a formulation with methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) was responsible for an allergic contact dermatitis ‘epidemic’. To control this phenomenon, a maximum allowed dose was set. However in 2005, MI alone was introduced in cosmetics, and this was followed by a new ‘epidemic’ of sensitization to MI and MCI/MI (1). We performed a retrospective study, consulting the medical files of patch tested patients reactive to ISs, from 2005 to 2013. MCI/MI was tested at 100 ppm in water (TROLAB® patch test allergens, Almirall Hermal