"Hyaluronic Acid (INCI often SODIUM HYALURONATE) itself is a substance that is widely found in human connective tissue in the skin. This complex molecule takes care of the moisture balance because of its strong hydrating properties.

Hyaluronic acid is a body’s own polymer, frequently occurring in the skin as one of the so called “glycosaminoglycans”, also called “mucopolysaccharides”, the ground substance of connective tissue. The water binding capacity of hyaluronic acid plays a key role in connective tissue, since it determines its viscosity to a high extend. The carbohydrates from which hyaluronic acid is build are alternating N-Acetylglucosamine and D-Glucuronic acid, building a non-branched polymer together. Hyaluronic acid is a polyanion because of the carboxylate functional group of D-Glucuronic acid. Hyaluronic acid is also an important part of cartilage and estimates highly its elastic properties. Furthermore, hyaluronic acid partly determines the viscosity of synovial fluid in the joints, where it has a lubricating function, enabling the joints to move smoothly.

- Molecular Weight: because hyaluronic acid is a polymer, it has a wide range of different molecular weights from 5000 to 20 Million Dalton, which results in a range of mutually varying properties. Low molecular weight is called for example 1 Million Dalton, since the molecular weight of hyaluronic acid in the human body is 4 to 5 Million Dalton on average, while the molecular weight of hyaluronic acid in synovial fluid is 3 to 4 Million Dalton.

- Signal molecules: in the human body hyaluronic acid is broken down on purpose by enzymes, called Hyaluronidases. These breakdown products are usually oligosaccharides and sometimes function as a signal molecule for fibroblasts, that produce new collagen and elastin. When hyaluronic acid is broken down even more, e.g. in the liver, the final decomposition products are a.o. water and carbon dioxide.
- Application: in cosmetics / skin care as a powerful moisturizer upon/in the skin (the horny layer) and also in cosmetic medicine as a (sub)dermal “filler”, in which case usually a cross-linked version is used. A third application in favour of the skin is cosmetic mesotherapy, where the hyaluronic acid is transferred into the skin, 1 mm down at the dermal-epidermal junction, where it stimulates the fibroblasts’ synthesis, resulting in extra collagen and elastin for the skin. "