Nanosystems in Photoprotection.

The ultraviolet (UV) radiation is responsible for stimulating acute responses in the human skin, those including positive responses like vitamin D synthesis along with negative ones such as erythema. The chronic effects of UV radiation include photoaging and cancer. Sunscreens are classified as organic and inorganic and the safety of the products containing them is related to the evaluation of the effects of these actives on the skin (irritation and sensitization) and also the possibility of cutaneous permeation that may cause the product to permeate into the bloodstream, possibly generating systemic toxicity. Nanotechnology plays an important role in overcoming the obstacles related to sunscreens. In this context, there are the nanosystems that have been widely used as vehicles to sunscreens. The use of nanosystems aims to reduce phototoxicity and cutaneous permeation of sunscreens and also to act in improving the photostability, the sun protection factor (SPF) and the protection spectrum of sunscreens. The most studied nanosystems in photoprotection are: liposomes, nanoparticles (lipid, polymeric and inorganic), cyclodextrins and nanoemulsions.