Methylisothiazolinone in Nail Polish Guide

Methylisothiazolinone or MIT, sometimes erroneously called methylisothiazoline, is a powerful biocide and preservative within the group of isothiazolinones, used in shampoos and body care products. Though long considered safe for use in cosmetics, two recent in vitro studies have shown that MIT is neurotoxic, causing damage to rat brain cells in tissue culture. Long-term health and safety studies have been conducted on animals, and thus far there is no evidence of nerve damage or neurological effects associated with MIT for consumers or workers. The two in vitro studies were published in peer-reviewed journals.[1][2] Regulatory authorities in the USA, Japan and Europe and more than 25 other countries have all independently concluded the product is safe. Despite these claims, the studies published in scientific journals suggest that additional testing may be needed. Initially, a similar conclusion was reached by them in 2003 (link below). In 2004, the European Scientific Committee on Cosmetic Products and Non-Food Products Intended for Consumers (SCCNFP) reported, "The SCCNFP is of the opinion that the proposed use of Methylisothiazolinone as a preservative at a maximum concentration of 0.01% (100 ppm) in the finished cosmetic product does not pose a risk to the health of the consumer."[3] The specific conclusions of this article are that: 1) data provided on physico-chemical properties on methylisothiazolinone are complete, 2) the percutaneous absorption study is inadequate. A 100% absorption (via the skin) is assumed, and 3) the in vivo unscheduled DNA synthesis assay is adequate. Methylisothiazolinone is considered non genotoxic/mutagenic. Whether Methylisothiazolinone poses a risk via other forms of exposure or in occupational settings during the manufacture of products containing the biocide has yet to be determined....