Methylisothiazolinone Dårligst Preservative No known benefits Methylisothiazolinone at a glance Also referred to as MI, or Kathon CG (when in an ingredient blend) Used as a preservative when combined with methylchloroisothiazolinone Is a well-known skin sensitizer Limited use in leave-on products at 7.5 ppm (parts per million) and rinse-off products at 15 ppm when in a blend Methylisothiazolinone description Preservative that’s generally recommended for use only in rinse-off products such as cleansers or shampoos. Methylisothiazolinone is known to be sensitising when used in leave-on products. Its use in both rinse-off and leave-on cosmetics products is restricted to low amounts as a means to avoid sensitivity while maintaining its efficacy as a preservative, but even in the low amount permitted (0.01%) has raised questions about it being more sensitising than most other preservatives. Related ingredients: Methylchloroisothiazolinone