Safety of titanium dioxide nanoparticles in cosmetics.

Nano-titanium dioxide in sunscreens doesn't penetrate beyond your skin's outer layer and doesn't enter your bloodstream—even on damaged skin. It's considered safe at concentrations up to 25%. The main concern: avoid inhaling it, which is why spray sunscreens and powders containing nano-TiO2 aren't recommended, though swallowing small amounts (like from lip balm) poses minimal risk.