The various forms of hyaluronic acid in cosmetics.

Hyaluronic acid is a complex sugar extremely hydrophilic, naturally present in the human body in the joints, muscles, eyes, and especially the skin. Almost 50% of its total amount is housed in the dermis, the deep layer of the skin. It constitutes the extracellular matrix and serves as a support for collagen and elastin fibers. It also ensures skin hydration as it acts like a molecular sponge : it captures water molecules and retains them.

However, over the years,the body's production of hyaluronic acid tends to decrease (a drop of about 6% per decade), which leads to skin sagging, the appearance of the first wrinkles, and a decrease in cellular activity… From the age of 50, it is thus proven that the stock of hyaluronic acid is halved ! In light of this, it is particularly beneficial to provide the skin with hyaluronic acid through dermocosmetic skincare applications. Indeed, this is less invasive and therefore significantly less risky than injections!

Hyaluronic acid comes in several versions, each offering different benefits.

• In its raw form (INCI: Hyaluronic Acid)

  This compound is referred to as high molecular weight (>1,800kDa)). It remains on the surface of the epidermis and creates a protective film that prevents water from evaporating. It also hydrates the superficial layers of the skin and provides a tightening effect.

• In its hydrolyzed form (INCI: Hydrolyzed hyaluronic acid)

  This refers to the hydrolyzed hyaluronic acid derived through an acid, an enzyme, or another hydrolysis method. Hydrolysis allows the fragmentation of hyaluronic acid into smaller size pieces. This process results in what is referred to as intermediate molecular weight (> 1,000-1,800kDa) hyaluronic acid. This is then stored in the skin's connective tissue and prevents water evaporation.

• In its alkaline form (INCI: Sodium Hyaluronate)

  Hyaluronic acid salts are often used due to their high stability and ease of incorporation into cosmetic formulas. They resist oxidation more than other types of hyaluronic acid. Moreover, this form of hyaluronic acid exists at a significantly lower molecular weight than pure hyaluronic acid and hydrolyzed hyaluronic acid. We refer to this as low molecular weight hyaluronic acid (> 50-1000kDa) . This penetrates deeper into the epidermis, reaching the base of the corneal structure, to revitalize the skin. It strengthens and stimulates the production of hyaluronic acid naturally produced by the body. It has a visible effect on reducing wrinkles and plumping the skin. Be aware, hyaluronic acid salts can also exist at high molecular weights, as in our hydrating serum .

• In its cross-linked form (INCI: Sodium Hyaluronate Crosspolymer)

  Low molecular weight hyaluronic acid salts are cross-linked to form a larger molecular weight molecule. This compound is new in skincare. It is interesting because it offers formulators the stability of hyaluronic acid salts and the moisturizing properties of larger molecular weight hyaluronic acids.

• In its acetylated form (INCI: Sodium Acetylated Hyaluronate)

  This form of HA is very recent in the beauty universe.Acetylation is a chemical reaction that allows the replacement of hydroxyl functions -OH of hyaluronic acid with acetyl groups CH₃CO. This form of hyaluronic acid thus possesses both lipophilic and hydrophilicproperties. It has an excellent affinity with the skin and high absorption. Research has shown that this ingredient absorbs three times more water than ordinary hyaluronic acid and ensures prolonged hydration. Moreover, in 2021, researchers highlighted the ability of acetylated hyaluronic acid to inhibit the release of MMP-1, which degrades collagen in mature skin and skin explants exposed to UV and urban dust. Acetylated hyaluronic acid also helped reduce crow's feet and naso-labial foldwrinkles (wrinkles running from the nose to the mouth). This form of hyaluronic acid is therefore particularly promising in combating the signs of aging!