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* A preservative

* Please read TIA's articles on Why Products Need Preservatives and Preservatives and Are They Safe


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 a potential allergen used in beauty products, although most reactions occurred in the 1980s and 1990s with leave in products, and it is now only used in much lower concentrations and in rinse off products, leading to much lower rates of allergic and irritant reactions, according to research.

Safety Measures/Side Effects:

In high concentrations Methylchloroisothiazolinone can cause chemical burns and it is a skin and membrane irritant. It was largely removed from most cosmetic products except for those with only short duration skin contact such as rinse-offs, although its inclusion in certain forms makes it more acceptable to sensitive users. It is used in concentrations of up to 15% in rinse-off products and 8% in other cosmetics (EWG). It is approved by the CIR for use in cosmetics.

Although there is some research claiming Methylchloroisothiazolinone causes cancer, no scientific data could be found to prove this link. According to research, the International Agency for Research on Cancer determined that Methylchloroisothiazolinone was not a carcinogenic.

In 2016, the Canadian goverrnment revised its Hot List to include additional warnings about this ingredient. Leave on products may no longer be formulated with this ingredient. As of June 2016, children's products with this ingredient can no longer be sold in Canada.

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