Zinc Stearate

Zinc stearate is an insoluble fatty-acid salt used mainly as a slip agent/anti-caking opacifier in powders and cosmetics, typically at low-to-moderate percentages, and it is generally considered non-irritating in standard skin-use patch testing. However, as a particulate material it can cause occasional mechanical irritation or dryness in highly reactive or eczematous skin (especially with friction/occlusion or compromised barrier), so it is best classified as very gentle rather than completely inert. Safety Notes: In commercial skincare and cosmetic-adjacent skin products, zinc stearate is often used at very low levels (~0.05–0.5%) as a slip/texture aid and anti-caking agent in leave-on creams/lotions and some sunscreens. The highest consumer-available use levels are seen in anhydrous/powder-heavy leave-on products (pressed powders, loose powders, powder foundations, some balm-to-powder formats), where zinc stearate commonly sits in the mid-single digits and can reach ~15–25% in high-slip, high-pressability specialty powders. It is uncommon in rinse-off formulas and, where used, typically remains at low functional levels for suspension/feel.