Insoluble nanoparticles like TiO2 and ZnO (common in sunscreens) don't penetrate living human skin. Toxicity tests found these nanoparticles are non-toxic, with no safety difference between nano and micro-sized versions. The evidence suggests nanoparticles in cosmetics pose no health risk, while their use in sunscreen provides major benefits like skin cancer protection.

Researchers reviewed existing in vitro (lab) and in vivo (human/animal) toxicity studies on cosmetic nanoparticles, examining whether they penetrate skin and cause harm through various safety tests including cytotoxicity, genotoxicity, and sensitization studies.

Funding not disclosed in abstract