The disadvantage of Titanium Dioxide is that it's not cosmetically elegant, meaning it's a white, "unspreadable" mess. Sunscreens containing Titanium Dioxideare often hard to spread on the skin and they leave a disturbing whitishtint. The cosmetic industry is, of course, really trying to solve this problemand the best solution so far is using nanoparticles. The itsy-bitsy Nano-sized particles improveboth spreadability and reduce the whitish tint a lot, but unfortunately, it also introduces new health concerns.

The main concernwith nanoparticles is that they are so tiny that they are absorbedinto the skin more than we want them (ideally sunscreen should remain on the surface of the skin). Once absorbed they might form unwanted complexes with proteins and they might promote the formation of evil free radicals. But do not panic, these are concerns under investigation. A 2009 review article about the safety of nanoparticles summarizes this, "to date, in-vivo and in-vitro studies have not demonstrated percutaneous penetration of nanosized particles in titanium dioxide and zinc oxide sunscreens". The English translation is, so far it looks like sunscreenswith nanoparticlesdo stay on the surface of the skin where they should be. Anyway, it doesn't matter if it reflects or absorbs, Titanium Dioxide is a pretty awesome sunscreen agent for two main reasons: it gives a nice broad spectrum coverage and it's highly stable. Its protection is very good between 290 - 350 nm (UVB and UVA II range), and less goodat 350-400 nm (UVA I) range. Regular sized Titanium Dioxide also has a great safetyprofile, it's non-irritating and is pretty much free from any health concerns (like estrogenic effect worries with some chemical filters).