Photoprotection in the era of nanotechnology.

Commercial sunscreen based on nano-sized titanium dioxide (TiO(2)) and zinc oxide (ZnO) delivers superior UV protection and reduces whitening on skin compared to the older generations of inorganic sunscreens. This review discusses the historical use of nano-sized TiO(2) and ZnO in sunscreen and the relationship between UV attenuation and the primary particles, aggregates and agglomerates that make up these inorganic oxides. In addition we reviewed the recent safety concerns surrounding these materials, specifically, percutaneous penetration of TiO(2) and ZnO nanoparticles through human skin and their potential to cause phototoxicity.