Hyaluronic Acid

Hyaluronic acid is a glycosaminoglycan built from repeating units of N-acetylglucosamine and D-glucuronic acid. Native HA spans a broad molecular-weight range, approximately 2 × 10^5 to 10^7 daltons.^{[7]Hyaluronic acid is a glycosaminoglycan built from repeating disaccharide units of N-acetylglucosamine and D-glucuronic acid, occurring natively across a very wide molecular-weight range of roughly 2 x 10^5 to 10^7 Da.Directly tested by the source[7] Juncan AM, Moisa DG, Santini A, Morgovan C, Rus LL, Vonica-Tincu AL, Loghin F. Advantages of Hyaluronic Acid and Its Combination with Other Bioactive Ingredients in Cosmeceuticals. Molecules. 2021 Jul 22;26(15):4429. PMID 34361586. PMCID PMC8347214. doi:10.3390/molecules26154429Tier 4}

Cosmetic labels may name hyaluronic acid, sodium hyaluronate or less commonly potassium hyaluronate. Sodium hyaluronate is the sodium salt of HA, not an unrelated substitute. The Cosmetic Ingredient Review assessed all three as one family of skin-conditioning ingredients used at concentrations up to 2%, although that US industry-funded panel has no UK regulatory authority.^{[10]Sodium hyaluronate is the sodium salt of hyaluronic acid; the CIR expert panel assessed hyaluronic acid, sodium hyaluronate and potassium hyaluronate together as a single family of skin-conditioning agents used in cosmetics at concentrations up to 2%, and concluded all three safe as used.Directly tested by the source[10] Becker LC, Bergfeld WF, Belsito DV, Klaassen CD, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW; Cosmetic Ingredient Review Expert Panel; Andersen FA. Final report of the safety assessment of hyaluronic acid, potassium hyaluronate, and sodium hyaluronate. International Journal of Toxicology. 2009 Jul-Aug;28(4 Suppl):5-67. PMID 19636067. doi:10.1177/1091581809337738Tier 4}

A 2021 review reported that HA itself appeared in about 5% of products marketed as containing HA and sodium hyaluronate in more than 95%. That market-share estimate came from a trade-magazine source written by ingredient-supplier authors rather than a peer-reviewed product survey.^{[7]iAlmost all cosmetic products marketed as containing hyaluronic acid in fact use sodium hyaluronate: a 2021 review reports HA itself appears in about 5% of such products while more than 95% contain sodium hyaluronate - though that figure is sourced to a trade-magazine article written by ingredient-supplier authors, not to a peer-reviewed survey.Inferred from adjacent evidence[7] Juncan AM, Moisa DG, Santini A, Morgovan C, Rus LL, Vonica-Tincu AL, Loghin F. Advantages of Hyaluronic Acid and Its Combination with Other Bioactive Ingredients in Cosmeceuticals. Molecules. 2021 Jul 22;26(15):4429. PMID 34361586. PMCID PMC8347214. doi:10.3390/molecules26154429Tier 4}

“Molecular weight” describes the size of the polymer chain. High-, low- and very-low-molecular-weight are not standardised consumer categories, and a finished product may combine several fractions. The molecular weight used in one study should not be inferred from a marketing term on another product.

Topical HA is a cosmetic ingredient. Recommending, applying and retailing a compliant topical cosmetic sit within aesthetic skincare practice.

In Great Britain, the finished cosmetic needs a UK-established Responsible Person, a Product Information File containing a cosmetic safety report and notification to OPSS before it is made available. This is a notification system, not pre-market approval of the finished product. HA and sodium hyaluronate do not appear on the prohibited or restricted ingredient lists.^{[11, 7]In Great Britain a topical hyaluronic acid product is a cosmetic under assimilated Regulation (EC) No 1223/2009 as amended by the Product Safety and Metrology etc. (Amendment etc.) (EU Exit) Regulations 2019: it needs a UK-established Responsible Person, a Product Information File containing a safety report, and notification to OPSS before being made available. The guidance sets out a notification duty rather than any approval step for finished products, with safety dossiers required only for new colourants, UV filters and preservatives. Hyaluronic acid and sodium hyaluronate do not appear on the restricted or prohibited ingredient lists.Directly tested by the source[11] Office for Product Safety and Standards (OPSS), Department for Business and Trade. Making cosmetic products available to consumers in Great Britain. GOV.UK guidance (accessed 1 August 2026)Tier 1[7] Juncan AM, Moisa DG, Santini A, Morgovan C, Rus LL, Vonica-Tincu AL, Loghin F. Advantages of Hyaluronic Acid and Its Combination with Other Bioactive Ingredients in Cosmeceuticals. Molecules. 2021 Jul 22;26(15):4429. PMID 34361586. PMCID PMC8347214. doi:10.3390/molecules26154429Tier 4}

Efficacy claims still require substantiation. A compliant product notification does not establish that a hydration, penetration, barrier-repair or wrinkle claim is true.

This entry is limited to topical cosmetics. Injectable HA fillers and skin boosters bypass the stratum corneum, sit under different product and practitioner rules, and have a separate evidence base. No topical study supports an injectable claim, and no injectable result supports a serum.

No ingredient-specific absolute contraindication to topically applied cosmetic HA was identified in the reviewed evidence. Suitability therefore turns on the exact finished formulation, its manufacturer instructions, the integrity of the application site and any previous reaction to that product or its other ingredients.

A topical product does not become suitable for injection because its label highlights purity, molecular weight or sterility. Any injectable use sits outside this entry and outside ordinary cosmetic-product use.

Low-molecular-weight HA fragments have been associated with some pro-inflammatory activity in mechanistic literature. The concern was acknowledged in an Evonik-led reconstituted-epidermis paper, but no clinical topical safety signal or exposure threshold was established. It is a formulation question rather than a general contraindication.^{[12]iLow-molecular-weight HA fragments have been reported to carry a degree of pro-inflammatory activity - a caveat acknowledged in the ingredient-industry literature itself, which framed the search for an optimal 50 kDa size precisely as an attempt to gain penetration without that risk.Inferred from adjacent evidence[12] Farwick M, Gauglitz G, Pavicic T, Kohler T, Wegmann M, Schwach-Abdellaoui K, Malle B, Tarabin V, Schmitz G, Korting HC. Fifty-kDa hyaluronic acid upregulates some epidermal genes without changing TNF-alpha expression in reconstituted epidermis. Skin Pharmacology and Physiology. 2011;24(4):210-7. PMID 21412035. doi:10.1159/000324296Tier 3}

Persistent swelling, urticaria, dermatitis or a reaction involving the eyes, airway or systemic symptoms is not a hydration problem and requires appropriate medical or emergency assessment.

Short-term hydration

Wrinkle appearance

Barrier function

The meaningful selection variables are the finished formulation, the outcome it has actually been tested for and the population and body site in that study. A molecular-weight claim is secondary unless the product supplies the measurement and evidence behind it.

A Raman micro-imaging study reported that 1,000–1,400 kDa HA did not cross the stratum corneum while 20–300 kDa HA did. Only limited study details are available in the accessible record, a co-author worked for HA supplier Soliance, and the finding has not been independently replicated. A second penetration study used reconstituted epidermis with a weaker barrier than intact human skin and was led by an Evonik employee.^{[1]In the single Raman micro-imaging study of human skin available, hyaluronic acid of 1000-1400 kDa did not cross the stratum corneum, while hyaluronic acid of 20-300 kDa did pass through it.Directly tested by the source[1] Essendoubi M, Gobinet C, Reynaud R, Angiboust JF, Manfait M, Piot O. Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy. Skin Research and Technology. 2016 Feb;22(1):55-62. PMID 25877232. doi:10.1111/srt.12228Tier 3[1, 12]The claim that low-molecular-weight HA penetrates rests on a very small evidence base: one Raman imaging study of human skin sections co-authored by an HA raw-material supplier, and one reconstituted-epidermis study led by an author at Evonik, a supplier of cosmetic HA. Neither is a clinical trial, and reconstituted epidermis has a substantially weaker barrier than intact skin.Directly tested by the source[1] Essendoubi M, Gobinet C, Reynaud R, Angiboust JF, Manfait M, Piot O. Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy. Skin Research and Technology. 2016 Feb;22(1):55-62. PMID 25877232. doi:10.1111/srt.12228Tier 3[12] Farwick M, Gauglitz G, Pavicic T, Kohler T, Wegmann M, Schwach-Abdellaoui K, Malle B, Tarabin V, Schmitz G, Korting HC. Fifty-kDa hyaluronic acid upregulates some epidermal genes without changing TNF-alpha expression in reconstituted epidermis. Skin Pharmacology and Physiology. 2011;24(4):210-7. PMID 21412035. doi:10.1159/000324296Tier 3}

The only in-vivo human quantification used tape stripping. It found HA in the stratum corneum at least eight times above baseline 24 hours after one application and at least 31 times above baseline after seven daily applications; the assay could not measure HA in viable epidermis or dermis. All authors worked for L’Oréal, which disclosed that it develops and sells HA products.^{[2]When topically applied HA has actually been measured in living human skin, it was quantifiable only in the stratum corneum: an in vivo tape-strip study found residual HA at least 8 times baseline 24 hours after one application and at least 31 times baseline after seven daily applications, while the assay could not measure HA in the viable epidermis or dermis at all.Directly tested by the source[2] Gregoire S, Man PD, Maudet A, Le Tertre M, Hicham N, Changey F, Boix-Segura G, Tran C, Vesperini L. Hyaluronic acid skin penetration evaluated by tape stripping using ELISA kit assay. Journal of Pharmaceutical and Biomedical Analysis. 2023 Feb 5;224:115205. PMID 36549259. doi:10.1016/j.jpba.2022.115205Tier 3}

No study was located showing topical HA reaching the human dermis in vivo. Selection should therefore be based on a surface-hydration aim and product-specific tolerability rather than a promise of “deep” delivery.

The instructions for the exact product govern application; the evidence does not establish a generic damp-skin, layering or frequency protocol.

Expected local effects

Molecular-weight uncertainty

Stopping and referral

Referral follows the presentation rather than the humectant. Unexplained facial swelling, persistent dermatitis, infection, a suspected medical cause of severe xerosis or a reaction outside ordinary cosmetic tolerance requires clinical assessment.

Questions about fillers, injectable skin boosters, vascular compromise, nodules or delayed inflammatory reactions are outside this topical entry and require the appropriately trained injectable or medical pathway.

A topical cosmetic may support surface hydration alongside medical care. It does not replace diagnosis or treatment of eczema, ichthyosis, renal or endocrine causes of xerosis, or another condition presenting as dry skin.

HA is highly hydrophilic. In a topical formulation it can retain water within the product film and the outer stratum corneum, changing surface hydration and capacitance. The size of the polymer influences diffusion, but “penetration” must name the compartment reached.

The available in-vivo measurement places residual topical HA in the stratum corneum, not the viable epidermis or dermis.^[2] The evidence for smaller HA crossing the stratum corneum comes from two small supplier-connected mechanistic studies rather than clinical trials.^{[1, 12]}

One laboratory vapour-sorption comparison measured HA absorbing 17.28% of its own weight in water at 43% relative humidity and 41.20% at 81% relative humidity. That experiment describes hygroscopy under laboratory conditions; it does not by itself predict a finished serum’s clinical effect.^{[9]iThe only measured hygroscopy figures located for hyaluronic acid come from a laboratory vapour-sorption comparison, in which HA absorbed 17.28% of its own weight in water at 43% relative humidity and 41.20% at 81% relative humidity - under half its own weight, not a thousand times it.Inferred from adjacent evidence[9] Sun X, Wang L, Fu R, Yang Y, Cheng R, Li J, Wang S, Zhang J. The chemical properties and hygroscopic activity of the exopolysaccharide lubcan from Paenibacillus sp. ZX1905. International Journal of Biological Macromolecules. 2020 Dec 1;164:2641-2650. PMID 32828891. doi:10.1016/j.ijbiomac.2020.08.129Tier 3}

“Hyaluronic acid holds 1,000 times its weight in water.”

“HA pulls water out of the skin in low humidity.”

“Low-molecular-weight HA penetrates deep and works from within.”

“Topical HA repairs the skin barrier.”

• The reported passage of 20–300 kDa HA through the stratum corneum has not been independently replicated; supplier documentation remains more informative than a generic “low molecular weight” label.^[1]
• The CIR panel’s unsupported statement that HA reaches the dermis conflicts with later compartment-specific studies; it should not be used for efficacy claims unless its underlying study can be identified.^{[10, 1, 2]The 2009 CIR safety assessment states flatly that hyaluronic acid does penetrate to the dermis, but without specifying molecular weight, species, dose or study design; it is an industry-funded safety review rather than an efficacy review, and its bare assertion conflicts with the molecular-weight-dependent picture in the imaging and tape-strip literature.Directly tested by the source[10] Becker LC, Bergfeld WF, Belsito DV, Klaassen CD, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW; Cosmetic Ingredient Review Expert Panel; Andersen FA. Final report of the safety assessment of hyaluronic acid, potassium hyaluronate, and sodium hyaluronate. International Journal of Toxicology. 2009 Jul-Aug;28(4 Suppl):5-67. PMID 19636067. doi:10.1177/1091581809337738Tier 4[1] Essendoubi M, Gobinet C, Reynaud R, Angiboust JF, Manfait M, Piot O. Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy. Skin Research and Technology. 2016 Feb;22(1):55-62. PMID 25877232. doi:10.1111/srt.12228Tier 3[2] Gregoire S, Man PD, Maudet A, Le Tertre M, Hicham N, Changey F, Boix-Segura G, Tran C, Vesperini L. Hyaluronic acid skin penetration evaluated by tape stripping using ELISA kit assay. Journal of Pharmaceutical and Biomedical Analysis. 2023 Feb 5;224:115205. PMID 36549259. doi:10.1016/j.jpba.2022.115205Tier 3}
• Capacitance may respond partly to the humectant film at the surface; visible and symptomatic outcomes should therefore accompany instrument numbers when a product is assessed.
• The low-humidity dehydration hypothesis is plausible but untested for HA; no special harm claim or universal damp-skin protocol can be justified.
• No clinical head-to-head study establishes whether HA or sodium hyaluronate performs better; the INCI name alone is not a quality ranking.^{[7, 10]}
• Long-term effects beyond 60 days and the clinical relevance of low-molecular-weight pro-inflammatory signalling remain unknown; claims should remain short-term and formulation-specific.^{[4, 12]}

Does topical hyaluronic acid reach the dermis?

Is sodium hyaluronate an inferior form?

Does HA need to be applied to damp skin?

Can topical HA repair a damaged barrier?

Is topical HA equivalent to a skin booster?

Each source is graded by evidence tier. Tier 4 material (manufacturer documents, expert consensus, practitioner experience) is useful for protocol and context, and is never presented as equivalent to independent clinical evidence.

1. Essendoubi M, Gobinet C, Reynaud R, Angiboust JF, Manfait M, Piot O. Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy. Skin Research and Technology. 2016 Feb;22(1):55-62. PMID 25877232. doi:10.1111/srt.12228Tier 3Supports: Raman micro-imaging of human skin, analysed as transverse skin sections. Verbatim result: 'HA with low molecular weight (20-300 kDa) passes through the stratum corneum in contrast of the impermeability of high molecular weight HA (1000-1400 kDa).' SCOPE LIMITS: this is the single most-cited source for the whole low-MW-penetration story and it is one small laboratory imaging study, not a clinical trial. The abstract does not state HA concentration, vehicle, exposure time, number of skin samples, or whether application was in vivo followed by biopsy or onto excised skin; the full text was paywalled and Wiley blocked retrieval, so these could not be verified. Detecting a Raman signature in a section is not proof of a biological effect. Nothing in the abstract claims HA reached the dermis.Funding / interest: Co-author R. Reynaud is affiliated to Soliance (Route de Bazancourt, Pomacle, France), a commercial manufacturer of cosmetic hyaluronic acid raw materials. The remaining authors are at the MEDyC/CNRS UMR 7369 unit, University of Reims. No funding statement is available in the PubMed record and the full text is paywalled.
2. Gregoire S, Man PD, Maudet A, Le Tertre M, Hicham N, Changey F, Boix-Segura G, Tran C, Vesperini L. Hyaluronic acid skin penetration evaluated by tape stripping using ELISA kit assay. Journal of Pharmaceutical and Biomedical Analysis. 2023 Feb 5;224:115205. PMID 36549259. doi:10.1016/j.jpba.2022.115205Tier 3Supports: Two-part study: ex vivo human skin to validate an ELISA for HA, then an in vivo human study with daily topical application of an HA formulation (containing both HMW-HA and LMW-HA) for 7 days, with 5 tape strips taken before and 2 hours after application on D0, D1 and D7. KEY VERBATIM FINDING: 'The ELISA assay was suitable for measuring HA in the SC but not epidermal or dermal layers.' Quantitation limits 200 and 3.1 ng/ml for both HA sizes. Residual HA 24 h after the first application was 'at least 8 times higher than before the first application and at least 31 times higher after 7 applications'. Tape-strip layers 1-2 were treated as surface 'residual film' and excluded; layers 3-5 were taken to represent the SC. SCOPE LIMIT: demonstrates HA accumulating in and on the stratum corneum with repeated use. It does not demonstrate delivery to viable epidermis or dermis; the assay could not measure those compartments at all.Funding / interest: ALL authors are employees of L'Oreal Research & Innovation, France. The competing-interest statement states verbatim: 'L'Oreal develops and sells consumer products containing hyaluronic acid.'
3. 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. Archives of Dermatological Research. 2024 Jun 3;316(6):329. PMID 38829483. doi:10.1007/s00403-024-03003-2. ClinicalTrials.gov NCT06178367Tier 2Supports: Double-blind randomised controlled trial, 36 nursing-home residents in Jakarta aged 60-80 with diagnosed dry skin. Intra-individual design: each participant received three randomised lotions (LMWHA, HMWHA, or vehicle) applied to three separate sites on the leg. Outcomes at weeks 0, 2 and 4: skin capacitance (SCap), transepidermal water loss (TEWL), specified symptom sum score (SRRC). RESULT at 4 weeks: LMWHA site had higher SCap than HMWHA (56.37 AU vs 52.37 AU, p=0.004) and than vehicle (56.37 AU vs 49.01 AU, p<0.001). VERBATIM NULL RESULT: 'All groups did not show any significant differences in TEWL and SRRC scores.' No side effects in any group. SCOPE LIMITS: n=36, 4 weeks, leg skin not face, elderly xerotic skin not general cosmetic use. The abstract does not state the actual kDa values used for 'LMWHA' and 'HMWHA'. Skin capacitance instruments respond to any high-dielectric material at the surface, including the humectant itself.Funding / interest: All authors are at the Department of Dermatology and Venereology, Universitas Indonesia / dr. Cipto Mangunkusumo National Referral Hospital, Jakarta. No industry affiliation is listed and no conflict-of-interest or funding statement appears in the PubMed record. This appears to be the only fully independent vehicle-controlled trial located for this entry.
4. Pavicic T, Gauglitz GG, Lersch P, Schwach-Abdellaoui K, Malle B, Korting HC, Farwick M. Efficacy of cream-based novel formulations of hyaluronic acid of different molecular weights in anti-wrinkle treatment. Journal of Drugs in Dermatology. 2011 Sep;10(9):990-1000. PMID 22052267Tier 2Supports: Randomised, vehicle-controlled, intra-individual (one eye vs the other) trial. 76 women aged 30-60 with periocular wrinkles applied one of five 0.1% hyaluronan formulations (50, 130, 300, 800 or 2000 kDa) twice daily for 60 days to one periocular area, with vehicle control cream around the other eye. Measurements at baseline, 30 and 60 days: skin hydration, skin elasticity (R2), and wrinkle depth from negative replicas by semi-automated morphometry (Ra mean roughness, Rz maximum roughness). RESULTS: all five HA creams significantly improved hydration and overall elasticity (R2) vs placebo. Wrinkle depth improved significantly ONLY in the 130 kDa and 50 kDa groups at 60 days vs the placebo-treated area. The authors' own interpretation of the wrinkle finding is explicitly speculative: reduction 'may be due to better penetration abilities of LMW HA'. SCOPE LIMITS: no effect sizes given in the abstract; only 2 of 5 molecular weights moved the wrinkle endpoint; 0.1% is one specific low concentration; never independently replicated.Funding / interest: PubMed lists only the first author's academic affiliation (Ludwig Maximilians University, Munich). The identical author cluster (Farwick, Gauglitz, Pavicic, Schwach-Abdellaoui, Malle, Korting) published a companion 2011 paper on the same 20-1500 kDa HA series in which lead author Mike Farwick is affiliated to Evonik Goldschmidt GmbH, Essen (PMID 21412035, source 12). Evonik supplies cosmetic HA raw materials. No funding or COI statement is retrievable from the PubMed record and the full text is paywalled, so the disclosure could not be read directly.
5. Jegasothy SM, Zabolotniaia V, Bielfeldt S. Efficacy of a New Topical Nano-hyaluronic Acid in Humans. Journal of Clinical and Aesthetic Dermatology. 2014 Mar;7(3):27-9. PMID 24688623. PMCID PMC3970829Tier 4Supports: 33 women, mean age 45.2, 8 weeks, periorbital region. Instruments: DermaTOP (3D wrinkle structure), Corneometer (hydration), Cutometer (elasticity), Chroma Meter (erythema), plus photographs rated by six trained raters. Reported headline figures: wrinkle depth reduced 'up to 40%', skin hydration 'up to 96%', firmness/elasticity 'up to 55%' at 8 weeks. CRITICAL SCOPE LIMIT: the abstract describes NO control or vehicle group and NO randomisation - every improvement is stated against the participants' own baseline. Uncontrolled 8-week moisturiser studies reliably generate large percentage gains from the vehicle alone. The widely quoted '40% wrinkle reduction' figure for topical HA traces to this uncontrolled 33-person study.Funding / interest: No funding statement appears in the PubMed record. Co-author S. Bielfeldt is CTO and Director of Research at proDERM Institute for Dermatological Research, Hamburg, a contract research organisation that performs efficacy testing for cosmetic manufacturers. The paper evaluates a commercial lotion/serum/cream range.
6. Zeichner J, Bussmann T, Weise JM, Maass E, Kruger A, Schade AK, Lain E, Mariwalla K, Kirchner F, Draelos ZD. Evaluation of Antioxidants' Ability to Enhance Hyaluronic-acid Based Topical Moisturizers. Journal of Clinical and Aesthetic Dermatology. 2024 Mar;17(3):48-51. PMID 38495545. PMCID PMC10941847Tier 4Supports: Cited here ONLY as documented evidence of how the '1000x' figure propagates through peer-reviewed literature. The paper's background states verbatim that HA is 'capable of binding up to 1,000 times its mass with water' - asserted as established fact in a peer-reviewed dermatology journal by an author group entirely tied to a cosmetics manufacturer, with no primary measurement offered. The paper's own experimental content is unrelated to that figure: glycine saponin induced endogenous HA synthesis in fibroblasts, and glycyrrhetinic acid decreased HA degradation rate by 54 percent. Those are in vitro fibroblast and enzyme results about antioxidants, not human outcomes and not about topical HA itself.Funding / interest: Five co-authors (Bussmann, Weise, Maass, Kruger, Schade) are Beiersdorf AG R&D employees and Kirchner is a Beiersdorf Inc employee. Zeichner and Mariwalla have consulted for Beiersdorf; Lain and Draelos are trial investigators/consultants/speakers for Beiersdorf among others. Every author has a Beiersdorf relationship.
7. Juncan AM, Moisa DG, Santini A, Morgovan C, Rus LL, Vonica-Tincu AL, Loghin F. Advantages of Hyaluronic Acid and Its Combination with Other Bioactive Ingredients in Cosmeceuticals. Molecules. 2021 Jul 22;26(15):4429. PMID 34361586. PMCID PMC8347214. doi:10.3390/molecules26154429Tier 4Supports: Narrative (non-systematic) review; full text read via PMC. Verified content: (a) HA is a glycosaminoglycan of repeating N-acetylglucosamine and D-glucuronic acid units, native molecular weights 'ranging from 2 x 10^5 to 10^7 Da'; (b) 'The list of substances that are restricted or prohibited in the EU for use in cosmetic products does not include hyaluronic acid and sodium hyaluronate'; (c) 'products that contain HA represent only 5%, while more than 95% of the total products contain sodium hyaluronate' - cited to Reynaud R et al., Personal Care 2017;9:61-63, a trade-magazine article by ingredient-supplier authors, not a peer-reviewed survey; (d) 'the high molecular weight of HA does not allow it to penetrate the deeper layers of the skin which restricts its benefits to topical effects'; (e) 'the HA skin penetration mechanism is still barely understood'; (f) the review states 'HA, which has the ability to bind water up to 1000 times its volume' and cites this to its references 93 and 94 - which I retrieved and identified as Pavicic 2011 (a clinical wrinkle trial that measured no water binding) and Souto et al., Applied Sciences 2020 (a nanomaterials review). Neither cited source contains a water-binding measurement.Funding / interest: Authors declare no conflict of interest. Note: first author A.M. Juncan is affiliated both to a university toxicology department and to SC Aviva Cosmetics SRL, Cluj-Napoca; the review includes a before/after figure of an anti-ageing cream supplied under a commercial test report (Report No. 300924/19/JSHR).
8. Barnes TM, Mijaljica D, Townley JP, Spada F, Harrison IP. Vehicles for Drug Delivery and Cosmetic Moisturizers: Review and Comparison. Pharmaceutics. 2021 Nov 26;13(12):2012. PMID 34959294. PMCID PMC8703425. doi:10.3390/pharmaceutics13122012Tier 4Supports: Cited as the traceable peer-reviewed origin point of the humidity teaching. VERBATIM: 'Humectants readily penetrate the SC and act like biological sponges by attracting and holding water in the skin, either by drawing it up from the dermis into the epidermis, or from the environment when the atmospheric humidity is >80%. They can also cause water to evaporate into the environment, and thus need to be used with occlusive agents to decrease or prevent TEWL.' HA is listed in the review's Table 2 as a humectant. CRITICAL SCOPE LIMIT: this assertion carries exactly two citations. I retrieved and read the full reference list: reference 25 is Danby SG et al., 'Vehicles for atopic dermatitis therapies: More than just a placebo', J Dermatolog Treat 2020 (a review) and reference 59 is Chang RK et al., 'Generic development of topical dermatologic products', AAPS J 2013 (a formulation/regulatory paper). Neither is an experiment measuring water movement out of the dermis, and neither concerns hyaluronic acid. This is review assertion citing reviews, not a primary finding.Funding / interest: All authors are employed in the Department of Scientific Affairs, Ego Pharmaceuticals Pty Ltd, Braeside, Victoria, Australia - a manufacturer of moisturisers and topical products. The authors state they declare no conflict of interest.
9. Sun X, Wang L, Fu R, Yang Y, Cheng R, Li J, Wang S, Zhang J. The chemical properties and hygroscopic activity of the exopolysaccharide lubcan from Paenibacillus sp. ZX1905. International Journal of Biological Macromolecules. 2020 Dec 1;164:2641-2650. PMID 32828891. doi:10.1016/j.ijbiomac.2020.08.129In vitroTier 3Supports: IN VITRO gravimetric moisture-absorption measurement, with hyaluronic acid as the benchmark comparator. VERBATIM: the novel polysaccharide's moisture absorption rates 'were 16.98% and 40.41% under the conditions of 43% and 81% relative humidity, which were close to that of hyaluronic acid (17.28% and 41.20%, respectively).' So measured HA water uptake from humid air was 17.28% of its own weight at 43% RH and 41.20% at 81% RH - under half its own weight even at high humidity. SCOPE LIMITS: dry-powder vapour sorption in a laboratory, not HA in a cosmetic vehicle and not on skin. Water taken up from air is a different quantity from the hydrodynamic volume a hydrated HA coil occupies in bulk solution. It is nonetheless a real, published, numerical measurement of HA hygroscopy - which is more than the '1000x' figure has.Funding / interest: Authors at the Center for Molecular Metabolism, Nanjing University of Science & Technology. Declaration of competing interest: 'None.' Note the commercial framing - the paper positions its novel polysaccharide as 'a good alternative to more expensive hyaluronic acid in the cosmetic industry' - so any bias would run toward understating HA, making these HA figures a conservative reference point rather than an inflated one.
10. Becker LC, Bergfeld WF, Belsito DV, Klaassen CD, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW; Cosmetic Ingredient Review Expert Panel; Andersen FA. Final report of the safety assessment of hyaluronic acid, potassium hyaluronate, and sodium hyaluronate. International Journal of Toxicology. 2009 Jul-Aug;28(4 Suppl):5-67. PMID 19636067. doi:10.1177/1091581809337738Tier 4Supports: Group safety assessment covering hyaluronic acid, sodium hyaluronate and potassium hyaluronate together, i.e. the free acid and its sodium and potassium salts are treated as one ingredient family. VERBATIM: 'Hyaluronic acid, sodium hyaluronate, and potassium hyaluronate function in cosmetics as skin conditioning agents at concentrations up to 2%. Hyaluronic acid, primarily obtained from bacterial fermentation and rooster combs, does penetrate to the dermis.' Not toxic across a range of acute animal toxicity studies in several species and exposure routes; not immunogenic; not a sensitiser in animal studies; not a reproductive or developmental toxicant; not genotoxic. Conclusion: safe for use in cosmetics as described. IMPORTANT SCOPE LIMIT: the assertion 'does penetrate to the dermis' is stated without qualification in the abstract, with no molecular weight, species, dose or study design attached. I could not retrieve the 63-page full report to establish what data it rests on (cir-safety.org returned HTML, not the PDF). The panel's remit was systemic safety, so this should not be read as an efficacy finding, and it conflicts with the molecular-weight-dependent picture in sources 1, 2 and 7.Funding / interest: The Cosmetic Ingredient Review is an expert panel funded by the Personal Care Products Council, the US cosmetics trade association. It is NOT a government regulator and its conclusions carry no legal force in the UK. Typed as expert-consensus rather than guideline or regulatory for that reason.
11. Office for Product Safety and Standards (OPSS), Department for Business and Trade. Making cosmetic products available to consumers in Great Britain. GOV.UK guidance (accessed 1 August 2026)Tier 1Supports: Cosmetic products in Great Britain are governed by 'Regulation (EC) No 1223/2009 on Cosmetic Products, as amended by the Product Safety and Metrology etc. (Amendment etc.) (EU Exit) Regulations 2019'. Every product must have a UK-established Responsible Person, who must hold a Product Information File including a safety report, and 'Before a cosmetic product is made available in GB, the Responsible Person must submit information on the cosmetic product to OPSS' via the Submit Cosmetic Product Notifications service. There is NO pre-market approval or licensing of finished cosmetic products; only new colourants, UV filters, preservatives and nanomaterials trigger specific dossier or notification requirements. SCOPE: this concerns topical HA products as cosmetics. Injectable HA (dermal fillers, skin boosters) sits under an entirely separate regime and is out of scope for this entry.
12. Farwick M, Gauglitz G, Pavicic T, Kohler T, Wegmann M, Schwach-Abdellaoui K, Malle B, Tarabin V, Schmitz G, Korting HC. Fifty-kDa hyaluronic acid upregulates some epidermal genes without changing TNF-alpha expression in reconstituted epidermis. Skin Pharmacology and Physiology. 2011;24(4):210-7. PMID 21412035. doi:10.1159/000324296In vitroTier 3Supports: Reconstituted human epidermis (a laboratory 3D tissue model, NOT human volunteers and NOT intact skin with a full stratum corneum barrier) incubated with HA at 20, 50, 130, 300, 800 and 1500 kDa. Findings: 50 kDa HA did not significantly alter TNF-alpha expression compared with 20 kDa HA, showed 'significantly higher skin penetration rates than larger sized HA', and was associated with increased expression of genes and proteins involved in tight-junction formation and keratinocyte cohesion. CONTEXT THE MARKETING OMITS: the paper's own background states 'Recent studies have demonstrated that low-molecular-weight HA (LMW HA) may show a certain proinflammatory activity' - the study existed to find a size that penetrates WITHOUT that risk. SCOPE LIMITS: reconstituted epidermis models have a markedly weaker barrier than real stratum corneum, so penetration rates measured in them cannot be transferred to intact human skin. No clinical outcome was measured.Funding / interest: Lead author Mike Farwick is affiliated to Evonik Goldschmidt GmbH, Essen, Germany - a commercial supplier of cosmetic hyaluronic acid raw materials. This paper establishes the Evonik link for the Pavicic 2011 author group (source 4). The stated aim is explicitly commercial product development: 'we thus aimed to characterize an LMW-sized HA molecule that combines strong anti-aging abilities with efficient skin penetration but lacks potential proinflammatory effects.'