Montmorillonite

Montmorillonite is a swelling clay used mainly as an absorbent/viscosity agent in masks and cleansers (often a few percent up to much higher in wash-off products), and it is not inherently chemically reactive on skin. Clinical experience and patch testing suggest low inherent irritancy, but its strong oil/water adsorption and mild abrasiveness can disrupt an already-compromised barrier or worsen dryness/eczema when used frequently or left on too long. Given sensitive-skin safety considerations, it is best classified as very gentle but not inert. Safety Notes: In commercial skincare, montmorillonite is used at very low levels (~0.05–0.5%) as a rheology modifier/suspending aid in emulsions, cleansers, and some gel/cream masks, where it primarily supports texture rather than oil absorption. Typical consumer clay masks and purifying cleansers commonly fall around ~5–20% active clay, while high-strength, consumer-available “100% clay” or “powder-to-paste” masks and bath/body clay products can reach ~40–60% montmorillonite once prepared/packed as high-solid systems (with water, humectants, and preservatives making up the balance). Leave-on masks tend to use higher levels than daily leave-on creams/lotions due to aesthetics and residue, and rinse-off formats can tolerate the highest solids loading.