Hydroxypropyl Methylcellulose

Hydroxypropyl methylcellulose is an inert, high–molecular weight cellulose-derived polymer used mainly as a thickener/film-former in topical products, typically at low concentrations (~0.1–2%). Clinical and patch-test experience shows it is very well tolerated with irritation being uncommon, though a small minority of highly reactive or barrier-compromised patients can experience transient stinging or rare contact reactions, so it is not scored as completely inert. Safety Notes: In commercial skincare, Hydroxypropyl Methylcellulose is commonly used at very low levels (~0.05–0.3%) as a secondary thickener/suspending and stabilizing aid in leave-on serums/lotions and rinse-off cleansers. Higher levels (about 1–3%) are seen in consumer gel-cream masks, peel-off/film-forming gels, and some high-viscosity styling/skin gels where it functions as a primary gellant/film former; the upper end (~4–5%) occurs in niche high-build gel or mask formats available OTC, with viscosity and film formation becoming the main practical constraint rather than a specific cosmetics regulatory limit.