Bentonite

Bentonite is an absorbent clay used mainly in masks/cleansers (often ~1–20%) to bind oil and impurities; it is not a classic chemical irritant but can be mechanically drying and barrier-disruptive. In sensitive or eczema-prone skin, this dehydration and friction can trigger stinging, tightness, or flare-ups, especially with frequent use or when combined with other drying actives. Patch tests are usually negative for true allergy, but the real-world irritation risk from xerosis and barrier compromise supports a mild score. Safety Notes: In commercial skincare, bentonite is used at very low levels (~0.1–1%) as a rheology modifier/suspending aid in cleansers, gels, and some masks, especially when paired with other thickeners. Most rinse-off clay masks and wash-off detox products sit around ~5–40% total clay, while high-strength consumer “pure clay” powders and single-ingredient clays sold for DIY facial masks can be 100% bentonite (anhydrous powder used as-is and hydrated by the consumer). Regulatory frameworks (US/EU) do not set a specific maximum for bentonite in cosmetics; practical limits are driven by texture, spreadability, and residue, with higher use levels most common in rinse-off formats.