Titanium dioxide (TiO2) — one of the 21 FDA-approved sunscreen chemicals with an approved usage level of 2 to 25 percent. When applied, titanium dioxide remains on the skin’s surface, scattering UV light. It is often used in conjunction with other sunscreen chemicals to boost the product’s SPF value, thus reducing the risk of irritation or allergies attributed to excessive usage of chemical sunscreens. Its incorporation into sunscreen formulations, makeup bases, and daytime moisturizers depends on the particular size of titanium dioxide employed. The smaller the particle size, the more unobtrusive TiO2’s application.