L'high-molecular-weight hyaluronic acid is the form with long chains, over 1,000 kDa: it does not penetrate the skin, but stays on the surface and forms a film that holds in water and limits evaporation. It helps hydrate, protect, and soothe the outermost layer — which is why treated skin looks smoother and feels more comfortable right away.
The difference in a nutshell: high-molecular-weight hyaluronic acid works on the skin, like a film that holds in moisture and protects. Low-molecular-weight hyaluronic acid passes through the surface layers and works within the skin, where it plumps. Neither is universally better: they do different things, and the best formulas combine them.
Let's take a closer look at the characteristics, benefits, and limitations of high molecular weight.
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High or low molecular weight: the differences
| High molecular weight (HMW) | Low molecular weight (LMW) | |
|---|---|---|
| Size | Over 1,000 kDa | Below 500 kDa |
| Where it acts | On the surface, does not penetrate | In the surface layers of the epidermis |
| What it does | Hydrating film, protects, soothes | Plumps, supports renewal |
| Perceived effect | Immediate, for smooth, comfortable skin | Gradual, on skin texture and fine lines |
| Ideal for | Dry, sensitive, reactive skin | Dehydrated skin with signs of aging |
Chemical structure and function
L'hyaluronic acid is a glycosaminoglycan made up of repeating disaccharide units of glucuronic acid and N-acetylglucosamine. Its ability to bind and retain large amounts of water makes it essential for skin hydration and structure.
Molecular weight is therefore a critical factor when choosing hyaluronic acid for a cosmetic formulation. For a general overview of the ingredient, see the dedicated entry on hyaluronic acid in cosmetics.
Benefits of high molecular weight
Hydration and surface protection
L'HMW-HA is particularly effective at holding water in the skin's surface layers, forming a film that reduces transepidermal water loss (TEWL). This is why skin treated with high-molecular-weight HA looks smoother and feels more comfortable right away.
Support for the skin barrier
The film that forms on the surface helps protect the skin barrier from external stressors, especially benefiting dry or dehydrated skin.
Soothing action
L'HMW-HA has been studied for its ability to modulate inflammatory mediators. This is one reason it is preferred in formulas designed for sensitive skin and reactive skin.
An interesting finding in the literature is that high and low molecular weights are not simply “more or less penetrating”; they have different biological behaviors. Long chains tend to have a more protective profile, while very short fragments have been associated, in some experimental models, with greater activation of inflammatory signals. This is why the best formulas combine several molecular weights rather than relying on just one.
Protection from environmental damage
The surface film limits direct contact with pollution and particulate matter, helping reduce oxidative stress caused by free radicals.
Uses of high-molecular-weight hyaluronic acid
In cosmetics, HMW-HA is used in:
- moisturizing formulas for dry and sensitive skin;
- treatments for reactive skin;
- anti-pollution and anti-aging serums;
- products to use after aesthetic treatments, for skin comfort.
L'high-molecular-weight hyaluronic acid is also used in medical settings — from ophthalmology to joint injections — but these are clinical contexts, with dosages and routes of administration completely different from those used in cosmetics.
It is worth keeping the two separate: a hyaluronic acid cosmetic product affects the appearance and comfort of the skin. It does not treat atopic dermatitis, psoriasis, ulcers or joint conditions, which should be referred to a doctor.
L'hyaluronic acid in LeLang products
The Hyaluronic Advance face cream combines patented hyaluronic acids with different molecular weights, so their surface film-forming and deeper actions work together.
HYALURONIC ADVANCE Plumping face cream with hyaluronic acid, filler effect Multiple hyaluronic acid: hydrates from deep within to the s... Discover HYALURONIC ADVANCE
L'Thermal Water Pro Age combines hyaluronic acid with Kudzu, for quick hydration and soothing relief throughout the day.
THERMAL WATER PRO AGE Anti-aging thermal water with hyaluronic acid Plumping spray toner with Valdieri Thermal Water, dual Hyaluronic Acid ... Discover THERMAL WATER PRO AGE
The Hyaluron 8 Hydra Deep serum takes this ingredient to the next level with 8 forms of hyaluronic acid: the high-molecular-weight fractions remain on the surface, forming a film, while the lighter ones complete hydration of the stratum corneum. Applied before Hyaluronic Advance, it complements its effects.
HYALURON 8 HYDRA DEEP Face serum with 8 forms of hyaluronic acid, hydrating and plumping 8 forms of hyaluronic acid with different molecul... Discover HYALURON 8 HYDRA DEEP
In the hyaluronic acid ingredient page, you’ll find a complete list of LeLang formulas that contain it.
You can also find LeLang products at partner pharmacies throughout Italy.
Frequently asked questions
What is high-molecular-weight hyaluronic acid used for?
It helps hydrate and protect the surface. By forming a thin film, it retains water in the outermost layers, reduces evaporation, and leaves skin instantly smoother and more comfortable. It also has a soothing effect, making it suitable for reactive skin. What it doesn’t do is reach the deeper layers: by definition, chains of that size stay on the surface.
Is high or low molecular weight better?
It depends on your goal, and the two aren’t competing. If your skin is dry, sensitive, or reactive, high molecular weight provides relief and protection. If you want to improve skin texture and fine lines, low molecular weight is also needed, as it works deeper down. A well-formulated product contains both: that’s why the label often says “hyaluronic acid with different molecular weights.”
What does kDa mean?
It’s short for kilodalton, the unit used to measure the weight of molecules. Cosmetic hyaluronic acid ranges from a few dozen kDa to over 2,000: the higher the number, the longer the chain and the more the product works on the surface. Reputable brands disclose this information.
Can they be used together?
Yes, and in fact it’s the most effective approach. They’re the same molecule in different sizes, so there’s no incompatibility: the low molecular weight works beneath the surface, while the high molecular weight seals in moisture on top. Most quality serums already combine them in the same formula.
Why does my skin sometimes feel tight after applying it?
Because hyaluronic acid attracts water, and in very dry conditions it can draw some of that water from the underlying layers rather than from the air. The solution isn’t to stop using it, but to apply it to slightly damp skin and immediately seal it in with a moisturizer: this keeps the retained water where it’s useful.
Is it for wrinkles?
For dehydration lines, the effect is visible and rapid, because well-hydrated skin makes them much less noticeable. For structural wrinkles, linked to the loss of collagen, hyaluronic acid alone is not enough: peptides and retinoids work on those.
Conclusion
L'High-molecular-weight hyaluronic acid is a versatile molecule with documented benefits, especially as a moisturizing, film-forming, and soothing agent. Its main strength is protecting the skin's surface; its limitation is that, by definition, it does not reach the deeper layers. For this reason, the most sensible choice in a well-formulated product remains a combination of different molecular weights.
Sources for this article
01 Cyphert J. M., Trempus C. S., Garantziotis S., "Size Matters: Molecular Weight Specificity of Hyaluronan Effects in Cell Biology", International Journal of Cell Biology, vol. 2015, article 563818, 2015. Review of the differences in biological signaling between high- and low-molecular-weight hyaluronic acid.
02 Review of the differential properties of hyaluronic acid and its fragments in the skin, with analysis of skin penetration, dermal pharmacokinetics, and immune activity, Journal of Pharmaceutical Investigation, 2023.
03 Regulation (EC) No. 1223/2009 on cosmetic products, Articles 2 and 20, and Regulation (EU) No. 655/2013 on common criteria for claims relating to cosmetic products.
On the site: hyaluronic acid in cosmetics · skin barrier · dry or dehydrated skin · peptides in cosmetics · hyaluronic acid ingredient profile
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