Methylisothiazolinone

Other names: MI, MIT, 2-methyl-2H-isothiazol-3-one

Harm score: 4 (Slightly harmful chemistry)

Methylisothiazolinone, also known as MI, MIT or 2-methyl-2H-isothiazol-3-one, is a chemical preservative that is added to many types of products for its antimicrobial properties. It is one of the so-called isothiazolinones, substances with a broad spectrum of biocidal effects that are able to kill a wide range of microorganisms, thus preventing their growth and overgrowth. Methylisothiazolinone therefore prevents the growth of bacteria, yeasts and moulds in products, thereby extending their life.

MI is used in a wide range of products, including cosmetics, cleaning products, industrial fluids, protective coatings and more. In cosmetics, it is typically found in products such as shampoos, conditioners, body lotions, skin creams, sunscreens and baby wet wipes. In cleaning products, MI is used for its antibacterial properties, being a component of soaps, washing powders, floor or dish cleaners and others. Industrially, it is used, for example, in the manufacture of paints and varnishes, but also in protective coatings for wood to prevent mould and rot. Methylisothiazolinone is also often used in cooling circuits in industrial sites because of its ability to prevent bacterial and algal build-up.