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 titanium dioxide

Inert earth mineral used as a thickening, whitening, lubricating, and sunscreen ingredient in cosmetics. It protects skin from UVA and UVB radiation and is considered to have no risk of skin irritation (Source: Skin Therapy Letter, 1997, volume 2, number 5). Because of its gentleness, titanium dioxide is an excellent sunscreen active for use on sensitive or rosacea-affected skin. It is also great for use around the eyes, as it is highly unlikely to cause stinging in this area.

Although titanium dioxide is a natural ingredient, pure titanium dioxide in nature is almost always adulterated with potentially harmful contaminants such as lead and iron. Therefore, titanium dioxide is purified via synthetic processes for use in cosmetics and sunscreens.

Titanium dioxide is typically micronized and coated for use in cosmetic products. The micronizing makes this somewhat heavy-feeling ingredient easier to spread on skin, not to mention making it more cosmetically elegant. Micronized titanium dioxide is also has much greater stability and can provide better sun protection than non-micronized titanium dioxide. Micronized titanium dioxide does not penetrate skin so there is no need to be concerned about it getting into your body (well, unless you eat the stuff). Even when titanium dioxide nanoparticles are used, the coatings employed have a larger molecular size that keeps the nanoparticles of titanium dioxide from penetrating beyond the uppermost layers of skin.

The coating process is done to improve application, enhance sun protection, and also to prevent titanium dioxide from interacting with other ingredients in the presence of sunlight, thus enhancing its stability. It not only makes this ingredient much more pleasant to use for sunscreen, but it improves efficacy and eliminates safety concerns. Common examples of ingredients used to coat titanium dioxide are alumina, dimethicone, glycerin, silica, and trimethoxy capryl silane.

Titanium dioxide as used in sunscreens also undergoes surface modification to ensure efficacy and stability. Examples of surface modifier ingredients used for titanium dioxide include stearic acid, isostearic acid, polyhydroxystearic acid, and dimethicone/methicone copolymer.

Additional sources: The Encyclopedia of Ultraviolet Filters, Allured Publishing, Nadim A. Shaath, PhD, 2007, pages 16-19; Skin Pharmacology and Applied Skin Physiology, Volume 14, Supplement 1, 2001, pages 92–97; Toxicology In Vitro, Volume 20, Issue 3, April 2006, pages 301–307; Toxicology Science, Volume 115, Issue 1, May 2010, pages 156–166. See UVA, sunscreens, UVB