Hyaluronic acid: the humectant for plumper, hydrated-looking skin

How it works

Hyaluronic acid works through three mechanisms simultaneously. First, as a humectant, each HA molecule binds water molecules through hydrogen bonding — helping bind available water within the upper layers of the skin and from the surrounding environment, plumping dehydrated surface skin from within². Second, molecular weight matters: high-molecular-weight HA forms a hydrating film at the skin surface³, while low- and ultra-low-molecular-weight HA can penetrate further into the upper layers of the epidermis⁴. The most effective formulas use a blend of multiple weights — different sizes serve different layers of skin's surface³ ⁴. Third, HA helps reinforce the appearance of the skin barrier and supports an overall lifted, supple-looking complexion over time¹.

The visible result of consistent use: skin that looks plumper, more comfortable, and visibly more hydrated⁶. Because HA pulls water from wherever it's most available, applying HA to slightly damp skin and sealing with a moisturizer is essential — otherwise HA can pull water from the deeper skin in dry environments.

Skin types & concerns it suits

• Dehydrated skin (any skin type): HA's humectant action plumps the look of surface dehydration on dry, oily, combination, and sensitive skin¹
• Oily and breakout-prone skin: HA is lightweight in serums and gels designed for oilier complexions
• Sensitive-feeling skin: generally well tolerated by reactive-feeling skin
• Mature skin and visible signs of skin aging: plumping the look of fine surface lines is one of HA's most visible short-term benefits⁷
• Compromised barriers: HA pairs well with ceramides and panthenol to support a more comfortable-looking, hydrated complexion⁹

How hyaluronic acid compares to other humectants and hydrators

Compared with glycerin — another well-studied humectant — HA tends to deliver a more visible plumping effect (especially in low-MW forms)⁴ but is heavier and benefits from sealing with a moisturizer in dry environments. Polyglutamic acid is a related humectant that may hold up to four times more water than HA per molecule and forms a film at the skin surface; the two are often paired for layered benefit. Sodium hyaluronate is the salt form of HA with a smaller molecular size, allowing it to hydrate without feeling greasy. Ceramides are not humectants but lipid barrier-supporting ingredients — pairing ceramides with HA delivers both moisture (HA) and the lipids that support the look of barrier comfort⁹. For a full hydration strategy primer, see The International Dermal Institute's Ingredients 101: Hydration — The Three-Layer Strategy for Moisture That Actually Lasts. For seasonal context on hydrating through environmental stress, see Essential Strategies for Winter Barrier Protection Series.

Tips for use

• Apply hyaluronic acid serums to slightly damp skin and seal with a moisturizer to lock hydration in
• Look for blends of multiple molecular weights for hydration that benefits multiple layers of skin's surface³ ⁴
• Use HA in both morning and evening for cumulative plumping benefits⁶
• In dry climates or environments, layer HA under an occlusive moisturizer or face oil to prevent reverse evaporation
• HA is suitable for all skin types — start daily and adjust based on personal preference for texture

Safety & considerations

• Hyaluronic acid is well tolerated by most skin types, including sensitive-feeling and breakout-prone skin
• Always consult your healthcare provider before introducing any new active during pregnancy or breastfeeding
• Used alone in very dry environments without a sealing moisturizer, HA can occasionally pull moisture from the deeper skin and feel drying — pair with a moisturizer to prevent this

Hyaluronic acid is one of the most universally loved hydrating ingredients in skin care¹ and appears across nearly every category — from mists and serums to moisturizers, cleansers, exfoliants, SPFs, eye treatments, and lip care. Formulas combining ceramides with hyaluronic acid help support barrier comfort alongside hydration⁹. Serums using multiple types of hyaluronic acid deliver potent humectant properties for long-lasting hydration, and calibrated blends of various molecular sizes work synergistically to provide hydrating benefits³ ⁴, with added antioxidant power, enhanced-looking elasticity², and improved-looking skin barrier strength for an overall lifted effect².

Beyond hyaluronic acid itself, a broader humectant family is often used in tandem. Sodium hyaluronate contributes lightweight hydration as part of a multi-form hyaluronic approach designed to support visible hydration. Polyglutamic acid replenishes skin's hydration reserves from within and helps plump the skin⁵. A phyto mucin blend of lotus root and glycerin helps attract moisture and support a comfortable, hydrated complexion. Together, these humectants help skin look plumper, more comfortable, and visibly more hydrated all day⁶.

For first-time users navigating which hyaluronic-acid product to choose, we recommend speaking with a skin therapist via Face Mapping skin analysis to find the right hydration strategy for your skin's specific needs.

FAQs

Q: What is hyaluronic acid?
A: Hyaluronic acid is a naturally-occurring glycosaminoglycan (a polysaccharide made of repeating disaccharide units) that can hold up to 1,000 times its weight in water², helping skin look plumper, more hydrated, and more comfortable¹.

Q: How does hyaluronic acid hydrate the skin?
A: It acts as a humectant — drawing and binding water into the stratum corneum² and reducing trans-epidermal water loss³. The result is a plumper, smoother-looking surface that helps minimize the appearance of fine lines and wrinkles⁷.

Q: What's the difference between hyaluronic acid and sodium hyaluronate?
A: Sodium hyaluronate is the salt form of HA with a smaller molecular size⁴, which is commonly used in lightweight serums and mists. Both deliver humectant benefits.

Q: Why do some formulas use multiple molecular weights of hyaluronic acid?
A: Different molecular sizes work at different layers of skin's surface. High-molecular-weight HA forms a hydrating film at the surface³; low- and ultra-low-molecular-weight HA penetrates deeper to deposit moisture in the upper epidermis⁴. A blend of weights gives more comprehensive hydration.

Q: What is polyglutamic acid, and how does it relate to hyaluronic acid?
A: Polyglutamic acid is a related humectant that is often used alongside HA for layered hydration support — helping replenish skin's hydration reserves and plump the look of skin⁵ ⁸.

Q: How should I apply hyaluronic acid?
A: Apply to slightly damp skin, then seal with a moisturizer. This helps lock hydration into the skin rather than letting it evaporate — particularly important in dry climates.

Q: Is hyaluronic acid suitable for all skin types?
A: Yes. HA is lightweight and is well-tolerated across skin types — including oily, sensitive-feeling, and breakout-prone skin.

Q: Can hyaluronic acid help with more than just hydration?
A: It can. Beyond hydration, HA helps strengthen the appearance of the skin barrier², helps seal in moisture against environmental stress¹, and supports a more lifted, supple-looking complexion over time¹.

Q: Can hyaluronic acid feel drying?
A: In very dry environments, HA used without a sealing moisturizer can occasionally pull moisture from deeper skin and feel drying. The fix is to apply HA to damp skin and seal with a moisturizer — particularly important in arid climates.

Q: Is hyaluronic acid safe during pregnancy?
A: Always consult your healthcare provider before introducing any new active during pregnancy or breastfeeding.

Further reading from The International Dermal Institute

• Ingredients 101: Hydration — The Three-Layer Strategy for Moisture That Actually Lasts
• Ingredients 101: Barrier Repair — The Science of Rebuilding Compromised Skin
• Skin Longevity: At The International Dermal Institute, We Believe…
• Essential Strategies for Winter Barrier Protection Series
• Lifestyle Factors for Winter Skin Health

References

1. Papakonstantinou E, Roth M, Karakiulakis G. Hyaluronic acid: A key molecule in skin aging. Dermato-Endocrinology. 2012;4(3):253-258.

2. Juncan AM, Moisă DG, Santini A, et al. Advantages of Hyaluronic Acid and Its Combination with Other Bioactive Ingredients in Cosmeceuticals. Molecules. 2021;26(15):4429.

3. Faga A, Nicoletti G, Gregotti C, et al. Pilot Comparative Study of the Topical Action of a Novel, Crosslinked Resilient Hyaluronic Acid on Skin Hydration and Barrier Function in a Dynamic, Three-Dimensional Human Explant Model. Journal of Drugs in Dermatology. 2016;15(4):434-441.

4. Essendoubi M, Gobber C, Cavezza A, et al. Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy. Skin Research and Technology. 2016;22(1):55-62.

5. Sung MH, Park C, Kim CJ, et al. Poly-γ-Glutamic Acid from a Novel Bacillus subtilis Strain: Strengthening the Skin Barrier and Improving Moisture Retention in Keratinocytes and a Reconstructed Skin Model. Molecules. 2025;30(3):619.

6. Piraccini BM, Alessandrini A, Starace M, et al. The 24-hour skin hydration and barrier function effects of a hyaluronic acid moisturizer. Clinical, Cosmetic and Investigational Dermatology. 2023;16:327-333.

7. Gruber JV, Gentry A, Engasser P, Draelos ZD. Efficacy Evaluation of a Topical Hyaluronic Acid Serum in Facial Photoaging. Clinical, Cosmetic and Investigational Dermatology. 2021;14:1005-1013.

8. Bhat AR, Irorere VU, Bartlett T, et al. In vitro evaluation of new functional properties of poly-γ-glutamic acid produced by Bacillus subtilis D7. Applied Microbiology and Biotechnology. 2015;99(2):737-748.

9. Schild J, Kalvodova A, Zbytovska J, et al. The role of ceramides in skin barrier function and the importance of their correct formulation for skincare applications. International Journal of Cosmetic Science. 2024;46(4):526-543.