Hyaluronic acid vs sodium hyaluronate: molecular weights and INCI names explained
Hyaluronic Acid, Sodium Hyaluronate, Hydrolyzed Hyaluronic Acid, crosspolymers: how the hyaluronic family appears on an INCI list, what molecular weight means and what the label leaves out.
Updated: 31 October 2026 · Reviewed by: Kamil Pyziak
What hyaluronic acid is
Hyaluronic acid is a long, chain-like sugar molecule (a polysaccharide) that occurs naturally in the body, including in the skin, where it is part of the material between cells and holds water. Because it binds water so well, it has become one of the best-known humectants in skin care.
The cosmetic raw material is today usually made by bacterial fermentation rather than extracted from animal tissue. In a product it works mainly on the surface and in the upper layers of the skin: it helps the skin hold water and gives serums and creams their typical smooth, slightly slippery feel.
Acid or salt: how it appears on the INCI list
The name you see most often is not Hyaluronic Acid but Sodium Hyaluronate, the sodium salt. In water the acid and its salts behave very similarly; the salt form is simply easier to handle in water-based formulas, so many products use it even when the front of the pack says “hyaluronic acid”. Potassium Hyaluronate is a less common salt of the same molecule.
Other members of the family are modified versions. Hydrolyzed Hyaluronic Acid and Hydrolyzed Sodium Hyaluronate are broken down into shorter chains. Sodium Acetylated Hyaluronate carries acetyl groups that make it somewhat more fat-friendly. Sodium Hyaluronate Crosspolymer is a cross-linked network that forms a gel and tends to stay on the skin surface.
Why molecular weight matters
Hyaluronic acid is not one size. The same INCI name, Sodium Hyaluronate, can cover chains of very different lengths, described by molecular weight and measured in daltons (Da) or kilodaltons (kDa). High-molecular-weight forms are large, form a film on the skin and give a noticeable smoothing, cushioning effect. Lower-molecular-weight and hydrolysed forms are smaller and are described as reaching further into the upper layers of the epidermis.
Research also suggests that fragments of different sizes can behave differently in the skin, and this is still an active area of study. For a consumer, the practical point is simpler: size influences how a product feels and where the ingredient stays, but bigger or smaller is not automatically better.
“Multi-weight” serums
Many serums advertise several molecular weights. On the INCI list this usually shows up as several entries, for example Sodium Hyaluronate, Hydrolyzed Sodium Hyaluronate and Sodium Hyaluronate Crosspolymer side by side. Sometimes, however, a single entry hides a blend of sizes supplied by the raw-material maker, so the number of entries does not always match the number of weights in the marketing.
Hyaluronic ingredients are almost always combined with other humectants, typically Glycerin, Propanediol, Butylene Glycol, Betaine or Sodium PCA, which do much of the water-binding work at higher concentrations.
How much is in the bottle
Hyaluronic ingredients are effective at low levels and become very thick in water, so they are used in small amounts. A large figure on the pack, such as “2% hyaluronic acid”, may refer to a ready-made solution or a blend rather than to the pure substance; the exact meaning depends on the brand.
Hyaluronic acid has a reputation for “drawing water out of the skin” in very dry air. Whether this matters in practice is debated. Formulas usually pair humectants with emollients or occlusives, and if a product feels tight on your skin, a richer cream on top is a common, simple solution.
Cosmetic serum vs injectable filler
Injectable hyaluronic acid fillers used in aesthetic clinics are not cosmetics. They fall under different rules and are administered by qualified professionals. A serum or cream with Sodium Hyaluronate works on the skin surface and cannot be compared with an injection.
Hyaluronic acid is generally well tolerated in cosmetics. If you have an unusual reaction to a product, the cause may be another ingredient in the formula, such as a fragrance or a preservative; a pharmacist or doctor can help if the skin stays irritated.
What the label does not tell you
The INCI list shows which hyaluronic forms are present, but not their molecular weight, origin or concentration. Two products both listing only Sodium Hyaluronate may contain very different grades of the same substance.
Position on the list gives a hint at best: hyaluronic ingredients are usually below 1%, where the order of ingredients is free. Judge the product by the whole formula and by how your skin responds rather than by a single star ingredient.