Mineral UV filter in sunscreens and a white pigment in toothpaste. Strong on UVB, weaker in long-wave UVA; the concerns are about inhaling or swallowing it, not skin contact.
Titanium dioxide does two jobs in this catalogue. In sunscreens it is a mineral UV filter: very effective against UVB and short-wave UVA, less so against long-wave UVA1, so it is usually paired with zinc oxide or an organic UVA filter. Like zinc oxide it is photostable and rarely causes allergy.
In toothpaste it is simply a white colourant (listed as CI 77891) that makes the paste look bright. It does not whiten teeth.
As a sunscreen filter its protection is measured directly in SPF testing, and it is one of the three filters the FDA currently regards as safe and effective (with zinc oxide and, since 2026, bemotrizinol). Safety questions concern other routes: EFSA concluded in 2021 that swallowed particles could not be ruled out as genotoxic, which ended its use as a food additive in the EU, and inhaled fine powder is classed as a possible carcinogen based on rat studies. Neither is a finding of harm from use on skin.
EFSA found no organ or reproductive toxicity at high doses, but could not rule out that swallowed titanium dioxide particles damage DNA, and concluded it could no longer be considered safe as a food additive. This led to the EU food ban; it is not a finding about skin use.