Titanium dioxide is the naturally occurring oxide of the element titanium. In cosmetics and personal care products, titanium dioxide functions as a sunscreen active ingredient, pigment, and thickener.
Titanium dioxide is classified as a physical sunscreen. Physical sunscreens protect the skin by using physical UV filters to block or deflect UV light. This is in contrast to chemical sunscreens, which protect the skin by first absorbing UV light, then transforming that light energy into some other form of energy, such as heat. Physical sunscreens tend to be better tolerated by most skin types because they are not absorbed into the skin. Thus, they are especially useful for those with heat sensitive skin (i.e. rosacea patients) as well as those with acne-prone skin as they are typically less pore-clogging. However, physical sunscreens are thicker than chemical sunscreens and can often leave a white cast after application.
Titanium dioxide is also used as a pigment in cosmetics that are intended to hide blemishes and brighten the skin. When titanium dioxide is used as a pigment, it may be referred to by the name CI 77891.