Hyaluronic acid is a kind of macromolecular mucopolysaccharide with d-n-acetylglucosamine and d-glucuronic acid as structural units. It is often called Sodium Hyaluronate or HA. Hyaluronic acid (HA) is widely distributed in the connective tissue of human body. Hyaluronic acid in the skin plays an important role in the metabolism of the epidermis. The destruction of hyaluronic acid
in human body or maladjustment, all can cause disease.