Ingredient Database

ToxicFree Foundation / Ingredient Database / Methylchloroisothiazolinone
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    What is it?

    Methylchloroisothiazolinone is a preservative often used in cosmetics and beauty products for its antibacterial and anti-fungal effects. 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.

    More Information

    Research on methylchloroisothiazolinone has shown that in pure form, it can be extremely irritating to the skin, causing itching, redness, and swelling. Diluted preparations are sold commercially for use in skin care products and other things that will be used on the skin. Most patients should not react to the dilute methylchloroisothiazolinone in these products, although people with extremely sensitive skin may develop contact dermatitis.

    If people notice itching, redness, and other signs of irritation after applying a product to the skin, they should wash the skin off and discontinue use of the product. It is advisable to consult a doctor to get information about likely allergens. People can also compare and contrast ingredient lists to see which ingredients tend to come up in products they react to. Sometimes, a variety of chemicals could be the culprit and some detective work may be required to find out why someone experiences skin reactions.


    This ingredient is commonly used in: