Methylchloroisothiazolinone is a chlorine-containing heterocyclic compound from the Isothiazolinone family. It is a white solid at room temperature and is highly soluble in water, glycols, and other alcohols.
Methylchloroisothiazolinone is a globally used broad-spectrum preservative for rinse-off and leave-on personal care and household products. Thanks to its biocide action, it effectively prevents the growth of bacteria, mold, yeast, and microalgae in minimal concentrations up to 0.01%. It is used in aqueous applications such as hair and body care, cleansing products, perfume, liquid soaps, etc.
Active in a wide range of pH values, Methylchloroisothiazolinone is compatible with almost all surfactants (anionic, cationic, and nonionic), proteins, and other antimicrobial agents, including fungicides.
The combination of Methylchloroisothiazolinone and another preservative from the Isothiazolinone family, Methylisothiazolinone, is known as Kathon CG, with an MCI/MI ratio of 3:1. Kathon CG is used in many products to prevent bacterial, mold, and fungal growth. It is used at minimal concentrations, in the range of 0.0003-0.0015%, and even at these levels, it reliably prevents microbial growth.Unfortunately, Methylchloroisothiazolinone is a known allergen (like Methylisothiazolinone) with many confirmed cases of contact dermatitis and sensitization. The first cases of contact dermatitis to these substances appeared in the mid-seventies, and later, there was a noticeable increase in frequency and severity.
In addition, it harms aqueous microorganisms and has a bad ecological profile. This preservative is not approved for use in pharmaceuticals and is restricted in some countries. It considered safe in personal care products if concentrations below 7.5 ppm in leave-on and 15 ppm in rinse-off products.
