Hyaluronic Acid Benefits: What the Research Shows

Hyaluronic acid (hyaluronan, or sodium hyaluronate in its salt form) is a long, unbranched sugar chain that the body makes for itself from glucose-derived building blocks. A 70-kilogram adult carries about 15 grams of it and, according to one review, cycles about 5 grams every day. It holds water in the skin, cushions and lubricates the joints, and fills the jelly of the eye. Because it is so central to these tissues, it is now used in many forms: joint injections, cosmetic fillers, creams and serums, capsules, eye drops, surgical gels and wound dressings.

This hub summarises what the research has found for each of these uses, and links to four deep-dive articles that cover the evidence in full. Findings are reported as the studies and reviews state them. Where reviews disagree, both sides are given. Doses mentioned are the doses used in trials, reported as trial facts.

Deep-Dive Articles

🧴

Hyaluronic Acid for Skin: Hydration, Wrinkles and Aging

How hyaluronan holds water in the skin, whether skin really loses it with age, the oral, topical and injected trials, and the side effects they recorded.

Read the deep dive →
🦵

Hyaluronic Acid for Joints: Injections, Oral Forms and Osteoarthritis

Synovial fluid in health and arthritis, the meta-analyses of joint injections from 2006 to 2022, what guidelines say, and the oral knee studies.

Read the deep dive →
👁️

Hyaluronic Acid for Eyes and Wound Healing

Hyaluronan in the vitreous, dry-eye drop meta-analyses, its use as a surgical gel in eye operations, and the Cochrane review of chronic wounds.

Read the deep dive →
💊

Hyaluronic Acid as an Antioxidant: Forms, Absorption and Safety

Whether hyaluronan is an antioxidant, the disputed animal studies of oral absorption, the forms compared, and safety findings across them.

Read the deep dive →

Back to Table of Contents

Table of Contents

  1. Deep-Dive Articles
  2. 1. Why One Molecule Has So Many Uses
  3. 2. Skin: Hydration and Wrinkles
  4. 3. Joints: Injections and Oral Forms
  5. 4. Eyes: Dry-Eye Drops and Surgical Gels
  6. 5. Wound Healing
  7. 6. The Antioxidant Question
  8. 7. Does Swallowed Hyaluronic Acid Reach the Body?
  9. 8. Safety Findings in Brief
  10. 9. The Evidence at a Glance
  11. Key Research Papers
  12. Connections

1. Why One Molecule Has So Many Uses

Hyaluronan is built from a repeating pair of sugars, glucuronic acid and N-acetylglucosamine (the same amino sugar family as glucosamine). Three enzymes in the cell membrane, the hyaluronan synthases HAS1, HAS2 and HAS3, assemble chains that can reach millions of daltons. Hyaluronidase enzymes and reactive oxygen species break it down again, and the body’s turnover is fast.

Two properties explain most of what follows. First, long chains trap large amounts of water and form a slippery, springy gel even at low concentrations, which is why the skin, joint fluid and eye depend on it. Second, size changes function: reviews describe large chains as space-filling and anti-inflammatory, while small fragments can act as inflammatory “danger signals”. A product’s molecular weight therefore matters, and studies of large and small hyaluronan sometimes reach different results.

Back to Table of Contents

2. Skin: Hydration and Wrinkles

Reviews state that about half of the body’s hyaluronan sits in the skin (in rats this was measured directly as more than half). Whether skin loses it with age is debated: a 1994 autopsy study found no significant change in concentration or chain size with age, only in how tightly it was bound to tissue, while later reviews describe a decline.

A 2025 meta-analysis of 7 randomized trials of swallowed hyaluronic acid reported significant improvements in skin hydration, elasticity and wrinkle depth, but not in firmness, wrinkle volume or water loss through the skin, and noted small samples and differences between trials. Individual trials used 120 mg a day for 12 weeks. In elderly people with dry skin, a low-molecular-weight lotion raised skin moisture more than a high-molecular-weight lotion or the plain base, with no side effects recorded. A meta-analysis of injected hyaluronic acid for skin quality found better hydration and radiance, but no change in elasticity or pigment.

Full detail: Hyaluronic Acid for Skin.

Back to Table of Contents

3. Joints: Injections and Oral Forms

Healthy joint fluid holds about 3–4 mg of hyaluronan per millilitre. In osteoarthritis and rheumatoid arthritis the hyaluronan is smaller and less concentrated, and one study found lower synthase and higher hyaluronidase activity in diseased joint linings.

Injecting hyaluronic acid into the knee (viscosupplementation) is where the evidence divides most sharply. A 2006 Cochrane review of 76 trials and a 2015 network meta-analysis reported benefits, though the latter’s authors pointed to the placebo effect of any joint injection. A 2012 meta-analysis found that large blinded trials showed a “clinically irrelevant” effect, and a 2022 BMJ analysis of 169 trials and 21,163 people found that large placebo-controlled trials showed a difference of about 2 mm on a 100 mm pain scale, below what patients notice. The 2019 American College of Rheumatology/Arthritis Foundation guideline conditionally recommends against these injections for knee osteoarthritis and strongly recommends against them for the hip. Studies of swallowed hyaluronic acid for knee pain were summarised in a review by researchers connected to a manufacturer.

Full detail: Hyaluronic Acid for Joints.

Back to Table of Contents

4. Eyes: Dry-Eye Drops and Surgical Gels

The vitreous jelly of the eye is where hyaluronic acid was first isolated, in 1934. Today it is used in artificial tears and as a viscoelastic gel that protects eye tissues during cataract and other eye operations.

The two dry-eye meta-analyses reached cautious conclusions. A 2017 analysis found hyaluronate drops better on one tear test (Schirmer) and worse on another (tear break-up time), concluding that neither type of drop was consistently superior and that the differences were not clinically significant. A 2021 analysis of 19 studies and 2,078 cases found a small improvement in tear production compared with drops without hyaluronic acid.

Full detail: Hyaluronic Acid for Eyes and Wound Healing.

Back to Table of Contents

5. Wound Healing

Hyaluronan takes part in each stage of wound repair, from inflammation to new tissue formation, and its effects again depend on chain size. A 2023 Cochrane review of 12 trials and 1,108 people found that, compared with a neutral vehicle (4 trials, 526 people), hyaluronic acid “probably improves complete ulcer healing”, with moderate certainty; comparisons with other active dressings were very low certainty. The same review found the evidence for pressure ulcers and diabetic foot ulcers insufficient; an older, smaller 2014 meta-analysis of diabetic foot ulcers had reported a benefit.

Back to Table of Contents

6. The Antioxidant Question

Hyaluronic acid is sometimes described as an antioxidant. The research shows something narrower. In test tubes it reacts with the hydroxyl radical: a 1994 study found that large hyaluronan protected cultured cells from hydroxyl-radical damage better than smaller hyaluronan, while a 2011 study found that small hyaluronan preparations scavenged several radicals and raised antioxidant-enzyme activity in mice. The two findings point in opposite directions on size.

In inflamed joints, reactive oxygen species break hyaluronan down; reviews describe it as a target of oxidation that is used up, not a recycled antioxidant. A major 2018 review states that its antioxidant role “has only been hypothesized, as it is not sufficiently supported by experimental data”. No human trial measuring hyaluronic acid as an antioxidant was found, which is why it is not grouped with vitamin C, vitamin E or glutathione.

Full detail: Hyaluronic Acid as an Antioxidant.

Back to Table of Contents

7. Does Swallowed Hyaluronic Acid Reach the Body?

The evidence comes from animals and is disputed. Radiolabel studies in rats and dogs found most of a swallowed dose in the faeces, yet some label reached joints, bone and skin; one rat study found gut bacteria break hyaluronan into small pieces that are absorbed in the large intestine and reach the skin. Another rat study found no significant absorption, only traces. The authors of the 2016 absorption study describe the question as “controversial”, and no human absorption study was verified.

The body’s own production uses glucose-derived sugars. Animal connective tissues, such as rooster comb, were the traditional extraction sources, and bone broth contains hyaluronan together with chondroitin; one rat study linked a broth fraction to slower bone loss. No verified source gives the hyaluronan content of a food.

Back to Table of Contents

8. Safety Findings in Brief

For knee injections, a 2021 safety meta-analysis of 35 trials and 8,078 patients found no difference from saline in adverse or serious adverse events, but more short-lived local reactions. Two other meta-analyses, in 2012 and 2022, reported more serious adverse events with viscosupplementation; the reviews disagree. For cosmetic fillers, a review of 48 trials found mostly brief injection-site reactions, with severe events rare. The topical lotion trial recorded no side effects, and the oral trials reported no safety signals in their abstracts, though no independent safety review of oral hyaluronic acid was found.

Back to Table of Contents

9. The Evidence at a Glance

Back to Table of Contents

Key Research Papers

  1. Fallacara A, Baldini E, Manfredini S, Vertuani S. Hyaluronic Acid in the Third Millennium. Polymers (Basel). 2018;10(7):701. PubMed PMID: 30960626
  2. Stern R. Hyaluronan catabolism: a new metabolic pathway. Eur J Cell Biol. 2004;83(7):317-25. PubMed PMID: 15503855
  3. Amin P, Sarabi A, Choe S, Scott S, Suh S, Mesinkovska NA. Oral Hyaluronic Acid Supplement: Efficacy in Skin Hydration, Elasticity, and Wrinkle Depth Reduction. J Drugs Dermatol. 2025;24(9):910-919. PubMed PMID: 40911749
  4. Hsu TF, Su ZR, Hsieh YH, Wang MF, Oe M, Matsuoka R, Masuda Y. Oral Hyaluronan Relieves Wrinkles and Improves Dry Skin: A 12-Week Double-Blinded, Placebo-Controlled Study. Nutrients. 2021;13(7):2220. PubMed PMID: 34203487
  5. Muhammad P, Novianto E, Setyorini M, Legiawati L, Yusharyahya SN, Menaldi SL, Budianti WK. Effectiveness of topical hyaluronic acid of different molecular weights in xerosis cutis treatment in elderly: a double-blind, randomized controlled trial. Arch Dermatol Res. 2024;316(6):329. PubMed PMID: 38829483
  6. Zhou R, Yu M. The Effect of Local Hyaluronic Acid Injection on Skin Aging: A Systematic Review and Meta-Analysis. J Cosmet Dermatol. 2025;24(1):e16760. PubMed PMID: 39807700
  7. Rutjes AW, Jüni P, da Costa BR, Trelle S, Nüesch E, Reichenbach S. Viscosupplementation for osteoarthritis of the knee: a systematic review and meta-analysis. Ann Intern Med. 2012;157(3):180-91. PubMed PMID: 22868835
  8. Pereira TV, Jüni P, Saadat P, Xing D, Yao L, Bobos P, Agarwal A, Hincapié CA, da Costa BR. Viscosupplementation for knee osteoarthritis: systematic review and meta-analysis. BMJ. 2022;378:e069722. PubMed PMID: 36333100
  9. Kolasinski SL, Neogi T, Hochberg MC, Oatis C, Guyatt G, Block J, Callahan L, Copenhaver C, Dodge C, Felson D, Gellar K, Harvey WF, Hawker G, Herzig E, Kwoh CK, Nelson AE, Samuels J, Scanzello C, White D, Wise B, Altman RD, DiRenzo D, Fontanarosa J, Giradi G, Ishimori M, Misra D, Shah AA, Shmagel AK, Thoma LM, Turgunbaev M, Turner AS, Reston J. 2019 American College of Rheumatology/Arthritis Foundation Guideline for the Management of Osteoarthritis of the Hand, Hip, and Knee. Arthritis Rheumatol. 2020;72(2):220-233. PubMed PMID: 31908163
  10. Miller LE, Bhattacharyya S, Parrish WR, Fredericson M, Bisson B, Altman RD. Safety of Intra-Articular Hyaluronic Acid for Knee Osteoarthritis: Systematic Review and Meta-Analysis of Randomized Trials Involving More than 8,000 Patients. Cartilage. 2021;13(1_suppl):351S-363S. PubMed PMID: 31735075
  11. Ang BCH, Sng JJ, Wang PXH, Htoon HM, Tong LHT. Sodium Hyaluronate in the Treatment of Dry Eye Syndrome: A Systematic Review and Meta-Analysis. Sci Rep. 2017;7(1):9013. PubMed PMID: 28827614
  12. Yang YJ, Lee WY, Kim YJ, Hong YP. A Meta-Analysis of the Efficacy of Hyaluronic Acid Eye Drops for the Treatment of Dry Eye Syndrome. Int J Environ Res Public Health. 2021;18(5):2383. PubMed PMID: 33804439
  13. Roehrs H, Stocco JG, Pott F, Blanc G, Meier MJ, Dias FA. Dressings and topical agents containing hyaluronic acid for chronic wound healing. Cochrane Database Syst Rev. 2023;7(7):CD012215. PubMed PMID: 37497805
  14. Presti D, Scott JE. Hyaluronan-mediated protective effect against cell damage caused by enzymatically produced hydroxyl (OH.) radicals is dependent on hyaluronan molecular mass. Cell Biochem Funct. 1994;12(4):281-8. PubMed PMID: 7834818
  15. Ke C, Sun L, Qiao D, Wang D, Zeng X. Antioxidant acitivity of low molecular weight hyaluronic acid. Food Chem Toxicol. 2011;49(10):2670-5. PubMed PMID: 21787831
  16. Soltés L, Mendichi R, Kogan G, Schiller J, Stankovska M, Arnhold J. Degradative action of reactive oxygen species on hyaluronan. Biomacromolecules. 2006;7(3):659-68. PubMed PMID: 16529395
  17. Kimura M, Maeshima T, Kubota T, Kurihara H, Masuda Y, Nomura Y. Absorption of Orally Administered Hyaluronan. J Med Food. 2016;19(12):1172-1179. PubMed PMID: 27982756
  18. Laznicek M, Laznickova A, Cozikova D, Velebny V. Preclinical pharmacokinetics of radiolabelled hyaluronan. Pharmacol Rep. 2012;64(2):428-37. PubMed PMID: 22661195
  19. Kyriazidis I, Spyropoulou GA, Zambacos G, Tagka A, Rakhorst HA, Gasteratos K, Berner JE, Mandrekas A. Adverse Events Associated with Hyaluronic Acid Filler Injection for Non-surgical Facial Aesthetics: A Systematic Review of High Level of Evidence Studies. Aesthetic Plast Surg. 2024;48(4):719-741. PubMed PMID: 37563436

PubMed Topic Searches

  1. Oral hyaluronic acid and skin: randomized trials
  2. Viscosupplementation for knee osteoarthritis: meta-analyses
  3. Sodium hyaluronate eye drops for dry eye
  4. Hyaluronan and the hydroxyl radical

Back to Table of Contents

Connections