Methylisothiazolinone: second ‘epidemic’ of isothiazolinone sensitization

doi:10.1111/cod.12200 Key words: allergic contact dermatitis; biocides; cosmetics; detergents; occupational. Isothiazolinones are used as biocides in a wide vari-ety of products, such as cosmetics, detergents, and industrial products. In the 1980s, a formulation with methylchloroisothiazolinone (MCI) and methylisothia-zolinone (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 Herma