The different types of hyaluronic acid in skincare.

Hyaluronic acid is an extremely hydrophilic complex sugar, naturally present in the human body in the joints, muscles, eyes and especially in the skin. Nearly 50% of its total quantity is found 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 the hydration of the skin because it acts like a molecular sponge: it captures water molecules and retains them.

Nevertheless, as the years go by, the body's production of hyaluronic acid tends to decrease (a drop of about 6% per decade), which leads to skin slackening, the appearance of the first wrinkles and a decrease in cellular activity. From the age of 50, it has been proven that the stock of hyaluronic acid is divided by two. Faced with this observation, it is particularly interesting to provide the skin with hyaluronic acid via dermocosmetic application. Indeed, this is less invasive and therefore much less risky than injections!

Hyaluronic acid comes in several versions, each providing different benefits for your skin.

• In its raw form (INCI: Hyaluronic acid).

  This compound is said to have a 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 moisturizes the surface layers of the skin and provides a tightening effect.

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

  This is the hydrolysate of hyaluronic acid derived by an acid, enzyme or other hydrolysis method. Hydrolysis allows the hyaluronic acid to be split into smaller fragments. It is thus possible to recover a hyaluronic acid of intermediate molecular weight (> 1,000–1,800kDa). This is then stored in the connective tissue of the skin and prevents water evaporation.

• In its alkaline form (INCI: Sodium Hyaluronate).

  The salts of hyaluronic acid are often used because of their great stability and their ease of incorporation in cosmetic formulas. They are more resistant to oxidation 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. It is called low molecular weight hyaluronic acid (> 100–1000kDa). The latter penetrates deeper into the epidermis, to the base of the corneal structure, to revitalize the skin. It reinforces and stimulates the production of hyaluronic acid naturally produced by the body. It has a visible effect on the reduction of wrinkles and plumps the skin. Attention, the salts of hyaluronic acid can also exist with high molecular weight, like in our hydrating serum.

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

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

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

  This form of HA is very recent in the beauty world. Acetylation is a chemical reaction that replaces hydroxyl (OH) functions in hyaluronic acid with acetyl CH₃CO groups. This form of hyaluronic acid thus has both lipophilic and hydrophilic properties. It has excellent affinity with the skin and high absorption. Research has shown that this ingredient absorbs three times more water than ordinary hyaluronic acid and guarantees prolonged hydration. In addition, in 2021, researchers demonstrated 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 light and urban dust. Acetylated hyaluronic acid has also been shown to reduce crow's feet and nasolabial fold wrinkles (wrinkles running from the nose to the mouth). This form of hyaluronic acid is therefore particularly promising in the fight against the signs of aging.