The New Sunscreens among Formulation Strategy, Stability Issues, Changing Norms, Safety and Efficacy Evaluations

Abstract

The sun-and-skin interactions have controversial sides. Besides important beneficial effects, we need to take into consideration also some serious harmful results. In particular, these are connected to the portion of the solar spectrum traditionally identified as ultraviolet type A and B. The topical application of sunscreens (and the avoidance of extreme exposure to sun rays) is worldwide recognized as the best strategy to avoid sunburn and oedema. Moreover, such strategy can efficiently prevent the onset of skin cancer. Therefore, the first aim of sunscreen products is to efficiently minimize all damage of sun exposure, while, at the same time, keeping good skin tolerability, avoiding safety problems and developing pleasant sensorial properties. Sunscreens, i.e., substances able to reflect and/or absorb, at a partial or complete extent, UV radiation are the key actors in skin protection. They are used to implement the level of primary photoprotection against UV rays. This means that when they absorb the radiation energy, their molecules pass to an excited state and successively re-emit energy in other forms (vibrational, rotational, infrared radiation) to come back to the ground state.