Methylchloroisothiazolinone  (5-chloro-2-methyl-4-isothiazolin-3-one), also referred to as MCI, is a preservative with antibacterial and antifungal effects within the group of isothiazolinones.



  • Methylchloroisothiazolinone is found in many water-based personal care products and cosmetics.
  • It was first used in cosmetics in the 1970s.
  • It is also used in glue production, detergents, paints, fuels, and other industrial processes. Methylchloroisothiazolinone is known by the registered tradename Kathon CG when used in combination with methylisothiazolinone.


  • Methylchloroisothiazolinone is a preservative often used in cosmetics and beauty products for its antibacterial and anti-fungal effects, according to Wikipedia. It’s most often seen in shampoos and other rinse-off products. It is part of a group of chemicals known as isothiazolinones, the most potent allergens on the consumer market. However, they are very effective preservatives and can be used safely.


  • Methylchloroisothiazolinone is an allergen and can cause severe skin reactions in some people. Since 2013 the use of the product particularly in cosmetics has received increased media coverage in the UK. In 2013 GP doctors asked cosmetics companies to remove it from products


Unknown, please consult with your doctor.

Other names



Source: Wikipedia,


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