What it is
Aluminum hydroxide is an inorganic compound with the formula Al(OH)3 used in cosmetics as a multifunctional mineral additive rather than as a UV filter. In sunscreens its key role is as a protective coating on mineral filter pigments such as titanium dioxide, where it helps quench the reactive oxygen species the pigment can generate under UV light. It also acts as an opacifier that makes formulas white and non-transparent, and in composite pigments it serves as a base that improves color coverage with less pigment. It contributes to texture by influencing viscosity and lending an emollient feel.
Origin & sourcing
It is an inorganic mineral compound; its naturally occurring crystalline form is the mineral gibbsite. For cosmetic use it is typically produced industrially as a fine, purified white powder used in coatings and as a base material in pigment systems.