Hyaluronic Acid is a naturally occurring glycosaminoglycan found in the extracellular matrix (ECM). Its primary function is to maintain hydration through its extreme hydrophilicity; a single gram of HA can bind up to six liters of water.

 In the dermis, HA provides the physical scaffolding for cells and acts as a reservoir for growth factors. When used as a filler, HA is chemically cross-linked to resist enzymatic degradation by hyaluronidase, extending its half-life from hours to several months while remaining biocompatible and reversible.