Introduction

 Hyaluronic acid occurs in high concentrations in some parts of body like dermis, the top layers of the epidermis and the connective tissue. It presents in the joint cartilage and the synovial fluid that fills the joint cavity; in the tendons and ligaments; in the vitreous body of the eye, where it was initially discovered, hair follicles also contain hyaluronic acid. Hyaluronic acid is metabolized quickly and is replaced daily in the skin and synovial fluids, thereby synthesis and degradation of hyaluronic acid for homeostasis in the body should be considered. It has an essential role for drug delivery, including nasal and ophthalmic administration.