Ingredients

Hyaluronic acid

Hyaluronic acid is a naturally occurring polysaccharide of the human extracellular matrix. In cosmetics, it is used almost universally as its sodium salt — sodium hyaluronate — as a humectant in moisturisers, serums and eye products sold throughout European parapharmacies.

At a glance

INCI names

Hyaluronic Acid; Sodium Hyaluronate; Hydrolyzed Hyaluronic Acid; Sodium Acetylated Hyaluronate

Chemical class

Linear glycosaminoglycan (polysaccharide) of repeating N-acetyl-D-glucosamine and D-glucuronic acid units

CAS numbers

9004-61-9 (hyaluronic acid); 9067-32-7 (sodium hyaluronate)

Regulatory class

Cosmetic ingredient (Regulation (EC) No 1223/2009); also used in injectable medical devices and medicinal products under separate regulatory regimes

Cosmetic function

Humectant, skin conditioning

What it is

Hyaluronic acid (HA) is a polysaccharide present in the extracellular matrix of connective tissues throughout the body, with particularly high concentrations in skin, the vitreous body of the eye, and synovial fluid. It is hydrophilic in the extreme: each molecule can bind many times its own mass in water through hydrogen bonding. This property is the basis of its cosmetic use.

In commercial production, HA is most often manufactured by bacterial fermentation (typically using strains of Streptococcus zooepidemicus or genetically modified bacterial hosts), which has displaced earlier sourcing from animal tissues such as rooster combs. The fermentation route yields high-purity material with controllable molecular weight, which matters for formulation (see below).

How it is used in parapharmacy products

HA is used as its sodium salt, sodium hyaluronate, because the salt is more water-soluble and more stable in finished products than the free acid. Typical usage concentrations in leave-on cosmetic products are at the low end — well below 1% by mass of the finished product — because the polymer is highly water-binding and any higher addition has a marked effect on viscosity and feel.

Cosmetic-grade sodium hyaluronate is available in a range of molecular weights, from "high molecular weight" (typically several hundred thousand to several million daltons) to "low molecular weight" or "hydrolysed" forms (oligomeric ranges, sometimes called hyaluronan oligomers). High-molecular-weight HA forms a thin hydrated film on the skin surface; lower-molecular-weight forms have, in principle, the potential to penetrate further into the upper stratum corneum. Marketing literature often makes much of this difference; the published evidence on clinical superiority of one molecular weight over another in routine cosmetic use is mixed.

Hyaluronic acid is listed in CosIng with cosmetic functions including humectant and skin conditioning. Sodium hyaluronate is listed with the same functions. The European Commission's CosIng is a record of declared cosmetic use, not an authorisation.

Regulatory status

Hyaluronic acid and sodium hyaluronate are not subject to specific restrictions in the Annexes of Regulation (EC) No 1223/2009. As with all cosmetic ingredients, their use is subject to the general safety requirement of Article 3 of the Regulation. The responsible person must include HA in the safety assessment for any finished product containing it.

HA in injectable form — dermal fillers — is regulated separately and falls outside cosmetic law: under the Medical Device Regulation, dermal fillers are explicitly addressed in Annex XVI as a group of products without an intended medical purpose that are nevertheless subject to the MDR. Injectable HA used for medical purposes (for example, intra-articular injection in osteoarthritis) is regulated as either a medical device or a medicinal product depending on its intended purpose and mode of action. None of these injectable uses fall within cosmetic law or within the cosmetic-product offering of a parapharmacy: this site addresses topical cosmetic use only.

Evidence summary

The evidence for topical hyaluronic acid as a humectant in finished cosmetic formulations is best characterised as well-established for its short-term skin-hydration effect. Controlled clinical studies have shown increases in stratum-corneum hydration and improvements in measures of skin smoothness following application of HA-containing formulations. The magnitude of the effect depends on the vehicle, the concentration and the population studied.

Claims that go beyond a humectant effect — for example, claims to "rebuild" the skin's structural HA or to act as a long-term anti-ageing intervention — are not supported to the same standard. Cosmetic claims must in any case comply with Commission Regulation (EU) No 655/2013 on common criteria for cosmetic claims.

Safety and known considerations

Topical hyaluronic acid is very well tolerated, with allergic contact dermatitis being rare. Sodium hyaluronate is also used as an ophthalmic medical device (artificial tears) and in this context has an established human-use safety record. There is no SCCS opinion restricting cosmetic use, and HA does not appear in Annex II or Annex III of Regulation 1223/2009.

Last reviewed: May 2026.