Methylparaben
Methylparaben (methyl 4-hydroxybenzoate, CAS 99-76-3) is the most commonly used paraben-type preservative in cosmetic formulations. It is a cheap, effective, and generally well-tolerated ingredient that helps prevent microbial contamination and extends the shelf life of cosmetic products. Its official CosIng function is listed solely as a preservative.
Methylparaben reliably prevents microbial growth in cosmetic formulas, helping to keep products safe and stable over time. It is considered well-tolerated at typical use concentrations.
A 2006 in-vitro study (Toxicology, Vol. 227, Issues 1–2) found that methylparaben-treated skin keratinocytes suffered greater UV-induced damage than untreated cells when exposed to sunlight. Although the study was not conducted on real people, the source recommends using a sunscreen alongside methylparaben-containing products. General paraben safety controversy also exists, though the source notes it is "mostly without scientific reason."
