Hyaluronic Acid in Topical Applications: The Various Forms and Biological Effects of a Hero Molecule in the Cosmetics Industry

Hyaluronic acid (HA) is a key molecule in cosmetics due to its hydration and biomechanical properties, as well as its ability to regulate cell functions. This review discusses the various forms of HA used in cosmetic formulations, their safety, and their ability to penetrate skin and hair. HA with a molecular weight below 100 kDa can penetrate the skin, with lower weights reaching the dermis. Clinical trials and independent reports confirm the safety of HA-containing products. The review highlights HA's beneficial effects on skin and hair, emphasizing its mode of action and potential new research areas, such as the vectorization of high-molecular-weight HA.