Hyaluronic Acid
Also known as: Hyaluronan, Sodium hyaluronate, HA
A skin-identical humectant that binds up to 1,000 times its weight in water — the hydration backbone of modern skincare.
In short
Hyaluronic acid (HA) is a sugar-like molecule (glycosaminoglycan) that occurs naturally in skin, joints, and eyes. Its defining talent is holding water: a single gram can bind up to 1,000 times its weight, and the skin's own HA keeps tissue plump and resilient. In skincare, HA is used as a humectant at 0.1–2%, drawing moisture into the skin's upper layers for immediate, visible plumping.
- Naturally present in skin, joints, and the eye's vitreous
- Can bind up to 1,000 times its weight in water
- Topical use: 0.1–2%, often as sodium hyaluronate or multi-weight blends
- Very low irritation risk — suits nearly all skin types
What is Hyaluronic Acid?
Hyaluronic acid is not an acid in the exfoliating sense — it is a polysaccharide that behaves like a molecular sponge. Your body holds roughly 15 grams of it, about half in the skin, where it keeps the extracellular matrix hydrated and cushions joints. Levels decline with age, which is part of why mature skin looks drier and less plump. Topical HA cannot replace lost deep-tissue HA, but as a humectant it dramatically improves surface hydration and, over weeks, the appearance of fine dehydration lines.
Where it comes from
Natural sources
- Human skin, joints, and eyes (endogenous production)
- Historically extracted from rooster combs (largely replaced)
- Fermented foods do not provide usable HA
How it's made
Cosmetic HA is produced by bacterial fermentation (Streptococcus cultures) and supplied in multiple molecular weights.
What it does in products
Benefits
Immediate and sustained hydration
strong evidenceRandomized trials show topical HA measurably increases skin hydration, reduces transepidermal water loss, and improves roughness — often within days.
Plumping fine lines
moderate evidenceBy hydrating the outer layers, HA temporarily plumps the skin, reducing the appearance of fine lines — a cosmetic effect that lasts as long as use continues.
Barrier and healing support
moderate evidenceHA is involved in tissue repair, and clinical experience shows it soothes and helps recovery after retinoid or procedural dryness.
Joint injections (medical use)
strong evidenceInjections of HA into arthritic knees (viscosupplementation) provide temporary lubrication and pain relief — a medical procedure distinct from skincare.
Side effects & safety
Safety considerations
- Topical hyaluronic acid is considered safe during pregnancy and is a common choice for pregnancy-safe hydration.
- None known; pairs well with virtually all actives.
- Not for: Known allergy (extremely rare)
How it's used
In supplements
Oral HA supplements (typically 120–240 mg daily) are marketed for skin and joints; small trials show modest skin hydration benefits, but the evidence base is smaller than for topical use.
In skincare
Serums typically contain 0.5–2% HA or sodium hyaluronate. Apply to damp skin, then seal with a moisturizer to lock the water in. Suitable morning and night.
Regulatory status
- Cosmetic ingredient under the FD&C Act; also an FDA-regulated medical device component when injected as a dermal filler. Dietary supplement when taken orally.
- GRAS (generally recognized as safe) for food use.
- INCI name on cosmetic labels: Hyaluronic Acid / Sodium Hyaluronate.
- The CIR Expert Panel has assessed HA and sodium hyaluronate as safe in cosmetics.
Popular products containing Hyaluronic Acid
- Hyaluronic Acid 2% + B5 — Multi-weight HA serumThe Ordinary · skincare
- Hydro Boost Water Gel — Iconic drugstore HA moisturizerNeutrogena · skincare
- Hydrating Hyaluronic Acid SerumCeraVe · skincare
Product names and brands are shown for reference and belong to their respective owners.
Molecular weight: why one HA is not like another
Hyaluronic acid comes in different chain lengths. High-molecular-weight HA sits on the skin's surface, forming a hydrating film; low-molecular-weight HA penetrates deeper but can, in high concentrations, be mildly irritating for sensitive skin. Most well-formulated products use a blend of weights to get both effects. Sodium hyaluronate, the salt form, has a lower molecular weight and is easier to formulate into stable products.
Frequently asked questions
Does hyaluronic acid work in dry climates?
Yes, with the right technique: apply it to damp skin and seal with a moisturizer or oil. Without ambient humidity or a seal, HA can draw moisture out of the deeper skin, which some people experience as tightness in desert or winter air.
Can I use hyaluronic acid with retinol or vitamin C?
Yes — HA is the great mixer of skincare. It buffers irritation and is commonly layered with retinoids, acids, and vitamin C. Apply HA first on damp skin, let it absorb, then your active, then moisturizer.
Is hyaluronic acid serum better than cream?
Not necessarily. Serums deliver higher concentrations to bare skin, but well-formulated creams also provide meaningful HA plus occlusives that reduce water loss. For dry skin, using an HA serum under a moisturizer is a stronger combination than either alone.
The bottom line
Hyaluronic acid is the safest, most reliable hydration tool in skincare. It will not rebuild collagen or erase deep wrinkles, but for visible plumping, tolerance, and layering compatibility, almost no ingredient matches it. Apply to damp skin and seal it in.
References
- Hyaluronic acid in dermatology — efficacy review. PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/?term=hyaluronic+acid+topical+skin+hydration
- Hyaluronic acid compound records. PubChem (National Library of Medicine). https://pubchem.ncbi.nlm.nih.gov/#query=hyaluronic%20acid
- Cosmetic Ingredient Review — hyaluronic acid safety assessment. Cosmetic Ingredient Review. https://www.cir-safety.org/ingredients
- Hyaluronic acid: a key molecule in skin aging. Dermato-Endocrinology (PMC). https://pmc.ncbi.nlm.nih.gov/articles/PMC3583886/