Toxicity assessment of nanoparticles in contact with the skin

Due to their unique physicochemical properties, engineered nanoparticles (NPs) are used in numerous skin products as sunscreen, texture agents, colorant, and drug delivery systems. While the skin is considered the first line of defense against xenobiotic entrance, the small size of NPs could promote the interaction with cutaneous cells. This review investigates the fate and the toxicological effects of organic and inorganic NPs used in cosmetic and dermatology. After direct exposure to skin cells, cytotoxicity, oxidative stress, inflammatory response, and genotoxicity were reported in a dose and time-dependent manner, especially for inorganic NPs. Despite these findings, the toxicity of nanoparticles applied to a healthy skin could be questioned due to their inability, for most of them, to reach the viable epidermis. Advanced skin models and toxicity tests validated for nanomaterials should be required for a better prediction of the dermal nanotoxicity.