Aluminium hydroxide Al(OH)3 is a synthetic ingredient found in many skin care products for example sunscreen lotions, body lotions, deodorants, toothpastes, lipsticks, foundations, shampoos, and others. It is used as a opacifying agent and skin protectant.
Many sunscreen lotions use aluminium hydroxide as a coating for titanium dioxide. The aluminium hydroxide prevents it from forming clumps and allows for an even application. This way it forms a layer on the skin surface and helps reflect UV rays away from the skin.
Although not all aluminium containing ingredients are safe in skin care, aluminium hydroxide is considered safe for use in cosmetic products.