The salt form of hyaluronic acid — what 'HA' on most clean labels actually means. The 2024–2025 sophistication is the multi-MW serum: combining ultra-low MW (≈5 kDa, deeper penetration), low MW (~50 kDa), medium MW (~1 MDa), and high MW (>1 MDa, surface film) for layered hydration. Vichy Minéral 89, Skinceuticals H.A. Intensifier, and The Ordinary's Multi-Peptide HA all formalize the multi-weight approach.
Benefits
graded hydration from surface film to upper-dermal depth
ultra-low MW fragments may signal repair (controversial but emerging data)
compatible with virtually any skincare system
Example uses
multi-MW hydration serums
post-acid recovery
injectable-adjacent topical 'HA boosters'
Mechanism of action
The sodium salt of hyaluronic acid — what almost every cosmetic 'HA' product actually contains. The salt form delivers better stability, lower viscosity for processing, and easier dispersion than the free acid, with chemically equivalent skin activity (the active is the same polysaccharide, with Na+ replacing the proton on the carboxylate). The 2024–2025 sophistication is the multi-MW serum: combining ultra-low MW (~5 kDa, theoretical CD44-mediated repair signalling), low MW (50 kDa, upper-epidermal hydration), medium MW (~1 MDa, stratum corneum film), and high MW (>1 MDa, surface occlusion). Cross-linked HA (in dermal fillers and a small number of topical wraps) is a structurally distinct product and not part of this entry.
Clinical evidence · High
Decades of clinical evidence inherited from the HA literature; head-to-head MW-fraction studies (Vichy Minéral 89, La Roche-Posay HyalU B5) support the layered hydration model; the ultra-low-MW signalling claim is more contested but emerging.
Effective concentration range
0.1–2% total HA (multi-MW blends rarely exceed 2% by weight)
Formulation notes
0.1–2% per MW fraction; total HA in a serum rarely exceeds 2% by weight. Crosslinked HA (in injectables and a few topical wraps) is a distinct category. Pairs with NMF (PCA, glycerin), peptides, and ceramides.
Watchouts
Low-humidity climates: HA without an occlusive can pull water from the dermis upward and outward, leaving skin drier. Always seal with a cream or oil.
The 'sodium hyaluronate vs hyaluronic acid' distinction is largely marketing — the molecule on skin is functionally equivalent; the form difference matters for the formulator, not the consumer. The ultra-low-MW signalling claim has both proponents (Vichy-funded work showing CD44 engagement and repair markers) and skeptics (concerns about pro-inflammatory effects of degraded HA in vivo); the dermatology consensus is unresolved.
Market positioning
The actual molecule on most 'hyaluronic acid' product labels — and a quiet example of the cosmetic-industry standard of using the salt form while marketing under the free-acid name. The MW-fraction sophistication is genuine and underused as a differentiator outside of dermatology-adjacent brands.
Comedogenicity
0 / 5
Sensitisation risk
Low
INCI & aliases
Sodium Hyaluronate
sodium hyaluronate · low molecular weight ha · high molecular weight ha · ha multi-weight · crosspolymer ha
Clean beauty perception
Universally trusted.
Products using Sodium Hyaluronate (HA Molecular-Weight Series)