Is methylisothiazolinone harmful to the skin?

The effects of methylisothiazolinone on the skin depend on how it is used: 1. Harmless situation: Methylisothiazolinone is a broad-spectrum biocide commonly used as a preservative in cosmetics to inhibit microbial growth and ensure product quality. When used at low concentrations and appropriate amounts, it typically does not cause harm to the skin. 2. Harmful situation: If the concentration is too high or the amount used is excessive, methylisothiazolinone may irritate the skin and cause allergic reactions such as itching and redness. In some cases, it may lead to contact dermatitis, with symptoms including erythema and papules. Individuals with allergic predispositions are particularly prone to these adverse effects.