Polyglutamic Acid in Korean Skincare: Does It Hydrate Better Than Hyaluronic Acid?
By Dr. Soo-Jin Kim · Seoul Cosmetic Chemist & Senior Editor, K-Ingredient
Updated Jun 2026Polyglutamic acid (PGA) shows up on the front of Korean serums and essences with one bold claim attached: it holds far more water than hyaluronic acid. The molecule is real, the chemistry is interesting, and there is some genuine lab evidence behind it. But most of the splashy numbers come from test tubes, not human skin, and that distinction changes the answer to whether you should swap your hyaluronic acid for it.
Polyglutamic acid (PGA) shows up on the front of Korean serums and essences with one bold claim attached: it holds far more water than hyaluronic acid. The molecule is real, the chemistry is interesting, and there is some genuine lab evidence behind it. But most of the splashy numbers come from test tubes, not human skin, and that distinction changes the answer to whether you should swap your hyaluronic acid for it.
This guide walks through what polyglutamic acid actually is, how it works on skin, what the published evidence does and does not support, and how it stacks up against hyaluronic acid in a real routine.
What polyglutamic acid is
Polyglutamic acid is a chain of glutamic acid units linked together into a long, water-loving polymer. The cosmetic version you see in Korean skincare is almost always gamma-polyglutamic acid (γ-PGA), made by fermenting Bacillus subtilis bacteria. If that sounds familiar, it should: the same fermentation is what makes Japanese natto, the sticky fermented soybean dish. The slimy, stringy texture of natto comes largely from γ-PGA.
On an ingredient label, you will see it as Polyglutamic Acid, Sodium Polyglutamate (the salt form, more stable and water-soluble), or Natto Gum. Korean brands lean on it because it fits the local skincare philosophy: layered, hydration-first, fermentation-friendly. K-beauty has used fermented ingredients for years, so a fermentation-derived humectant slots in naturally next to galactomyces, snail mucin, and rice extract.
A humectant is an ingredient that pulls and holds water. Glycerin is one. Hyaluronic acid is one. Polyglutamic acid is one too. The marketing question is not whether it hydrates. It does. The question is whether it hydrates better than the humectant it is usually compared to.
Where the "natto" origin matters
Because γ-PGA is the same biopolymer found in a food eaten safely for centuries, its safety baseline is reassuring. It is biodegradable, water-soluble, edible, and not known to be immunogenic at cosmetic levels. That food history is part of why it moved into skincare with so little friction. It does not, by itself, prove the molecule does anything special on your face. Origin and efficacy are two separate questions.
It is worth knowing that γ-PGA is a workhorse industrial biopolymer well beyond cosmetics. Reviews of the molecule describe applications across food, agriculture, water treatment, drug delivery, and medicine, thanks to its water solubility, biodegradability, and ability to bind metal ions and form gels and films (Elbanna et al., 2024, Front Microbiol). The skincare use is a small, relatively recent branch of a much larger tree. That breadth is a point in favor of its safety and manufacturability, but it also means a lot of the impressive lab data you find about γ-PGA was generated for non-skin uses and should not be read as proof of facial benefit.
How it works on skin
Polyglutamic acid is thought to hydrate through three mechanisms. The strength of evidence behind each one is very different, so it helps to separate them.
1. It forms a moisture-trapping film on the surface. Because γ-PGA used in cosmetics is a large, high-molecular-weight polymer, it mostly stays on top of the skin rather than sinking in. It spreads into a thin, breathable film that slows water from evaporating off the surface. This is the most reliable, least controversial part of the story. Film-forming humectancy is straightforward physics, and it is well documented for large polymers in general.
2. It may boost your skin's own natural moisturizing factor (NMF). NMF is a built-in cocktail of small molecules in the outer skin layer that grab and hold water: pyrrolidone carboxylic acid (PCA), lactic acid, urocanic acid, and others. Several sources report that polyglutamic acid raises these NMF components. This claim is plausible and frequently repeated, but the human data behind it is thin and mostly comes from older or industry-linked testing rather than large independent trials.
3. It may slow the breakdown of your skin's existing hyaluronic acid. Your skin makes its own hyaluronic acid, and an enzyme called hyaluronidase chops it up over time. Polyglutamic acid can inhibit hyaluronidase in lab settings. In theory, less hyaluronidase activity means your natural hyaluronic acid lasts longer, keeping skin plumper. This is mechanistically interesting but, again, demonstrated mostly in test-tube enzyme assays, not on living human skin.
There is also newer cell-based evidence worth noting. A 2025 lab study on γ-PGA from a Bacillus subtilis strain found that, in cultured skin cells and a reconstructed 3D skin model, γ-PGA dose-dependently increased markers of the skin barrier (filaggrin, involucrin, loricrin), raised hyaluronic acid synthase activity, and boosted aquaporin-3, a water channel involved in hydration (Ko et al., 2025, Int J Mol Sci). That is a promising signal. The authors themselves flag the catch: there was no in vivo human data to confirm any of it translates to real faces.
The honest grade on mechanism
The surface film-forming effect is well supported. The deeper claims (NMF boosting, hyaluronidase inhibition, barrier-gene activation) are biologically plausible and supported by cell and test-tube work, but not yet by strong human trials. That is the gap to keep in mind when a label promises long-term firming or anti-aging from PGA.
What the evidence actually shows
Here is where the marketing and the published science diverge most. The two figures you will see everywhere are: PGA holds up to 4 times more water than hyaluronic acid, and PGA can hold up to 1,180 times its own weight in water. Both numbers trace back to laboratory water-absorption assays, not to skin.
A test-tube hygroscopicity test measures how much water a powder grabs out of humid air or how much a gel can soak up in a dish. That tells you about the raw material. It does not tell you how much extra hydration your cheek gets from a 0.2% concentration mixed into a serum with twenty other ingredients. Real-world skin hydration depends on concentration, the rest of the formula, how it is layered, and your own skin. The "4x" claim is real as a lab result and misleading as a skincare promise.
The small human-ish studies
The most-cited "head to head" data point is a small comparison in which a polyglutamic acid formula raised corneometer-measured hydration more than a glycerin formula two hours after application, with a handful of volunteers. Tiny sample, short window, and it compared PGA to glycerin, not to hyaluronic acid. Useful as a hint. Not proof of superiority.
A 2014 in vitro study on γ-PGA from Bacillus subtilis D7 measured a hygroscopicity of 86.8% and water retention of 56.9% after prolonged exposure, and the authors referenced earlier work suggesting γ-PGA outperformed collagen and hyaluronic acid for moisturizing in lab conditions (Lee et al., 2014, Saudi J Biol Sci). Again: lab conditions, not a clinical trial on people.
One of the more complete data sets actually comes from an unusual source: cucumbers engineered to produce γ-PGA. In that study, topical application of the γ-PGA-rich extract increased skin water content by 6–14%, decreased water loss by 11–12%, reduced facial wrinkles by about 20%, and modestly improved elasticity and brightness (Li et al., 2024, Int J Biol Macromol). This included some human skin testing and is among the better signals available. But it tested a specific plant-derived extract, not a standard cosmetic PGA serum, so you cannot read it straight across to the bottle on your shelf.
How the evidence grades out
| Claim about PGA | Type of evidence | Honest grade |
|---|---|---|
| Acts as a humectant, hydrates the surface | Lab assays + small human tests | Strong |
| Forms a moisture-trapping film, reduces water loss | Polymer physics + lab/extract studies | Moderate to strong |
| Holds 4x more water than HA / 1,180x its weight | In vitro absorption assays only | Real number, misleading for skin |
| Raises NMF (PCA, lactic acid) on skin | Sparse, mostly industry-linked | Weak |
| Inhibits hyaluronidase to preserve skin's own HA | Test-tube enzyme assays | Weak (plausible, unproven on skin) |
| Boosts barrier genes, HA synthase, aquaporin-3 | Cell + 3D skin model, 2025 | Promising but in vitro only |
| Long-term anti-aging / firming on real faces | No strong human RCTs | Insufficient |
The overall picture: polyglutamic acid is a legitimate, effective surface humectant with a thin but growing science base. The deeper and longer-term claims run ahead of the published human evidence. For a YMYL-honest read, treat PGA as a good hydrator, not a proven anti-aging actor.
Why the human evidence is still thin
It is fair to ask why a molecule this popular has so little direct human trial data. Part of the answer is money and incentives. Large, placebo-controlled skin trials are expensive, and humectants like PGA do not need them to be sold; a manufacturer can support marketing claims with corneometer readings on a small panel and in-vitro absorption numbers. There is little commercial pressure to run a 100-person, dermatologist-graded study comparing PGA head-to-head against hyaluronic acid over months. So the literature fills up with mechanism papers, cell studies, and small short-term tests, while the big confirmatory trials simply do not get funded.
A live search of the medical literature makes the gap visible. You can run the search yourself: polyglutamic acid skin hydration on PubMed returns a modest set of mostly in-vitro and mechanism papers, while the comparable hyaluronic acid topical skin hydration search returns a far deeper and more clinical body of work. That contrast is the honest summary of where the two ingredients stand. None of this means PGA is ineffective. It means the confidence behind its claims should be lower than the confidence behind hyaluronic acid's.
PGA vs hyaluronic acid: the real comparison
This is the matchup the topic asks about, so let's be direct.
Hyaluronic acid has the deeper, more mature clinical record. Topical hyaluronic acid has been studied in far more human trials, and reviews of that work report meaningful improvements in hydration, fine lines, elasticity, and skin barrier function, with good tolerability (Bravo et al., 2022, Dermatologic Therapy). HA also comes in a range of molecular weights. High-molecular-weight HA sits on the surface and films like PGA does; lower-molecular-weight HA can penetrate the upper layers and hydrate deeper. That versatility is one of HA's real advantages.
Polyglutamic acid's edge is mostly at the surface. Because cosmetic PGA is large, it tends to stay on top and form that occlusive-ish film, which can make skin feel smoother and look dewier fast, and may slow surface water loss a bit more effectively than a thin HA layer alone. Some people find PGA feels less "tight" than HA as it dries. That is a texture and short-term-feel advantage, not a proven hydration-depth advantage.
The most important practical point: they are not rivals. PGA and HA work on slightly different levels (surface film vs. multi-depth humectancy), so layering both is the common Korean approach. HA first on damp skin to pull water in, PGA on top to help hold it, then a moisturizer to seal. You do not have to pick a winner.
| Factor | Polyglutamic acid | Hyaluronic acid |
|---|---|---|
| Source | Bacillus subtilis fermentation (natto origin) | Bio-fermentation or animal-derived |
| Where it acts | Mostly skin surface (film) | Surface and, at low MW, deeper layers |
| Human clinical evidence | Thin, emerging | Large, mature |
| Lab water-holding | Very high (in vitro) | Very high (in vitro) |
| Best at | Sealing in moisture, dewy finish | Versatile multi-depth hydration |
| Plays well with the other? | Yes, often layered together | Yes, often layered together |
| Verdict | Good surface humectant | Better-proven all-rounder |
So, does PGA hydrate better than HA? On a single in-vitro number, yes. On the weight of human evidence, no. Hyaluronic acid is the better-proven hydrator overall. Polyglutamic acid is a strong, pleasant-feeling complement that may seal moisture in slightly better at the surface. If you want one workhorse, HA is the safer evidence-backed choice. If you want a dewy finish and barrier-feel boost on top, PGA earns its place.
For more on how these humectants slot into a hydration-focused routine, see our guides on hyaluronic acid compared to snail mucin and building a routine for dehydrated skin.
Other hydrating actives worth knowing
PGA and HA are not the only humectants in the K-beauty toolbox, and a couple of them have their own evidence stories.
- Glycerin. The boring, cheap, deeply proven humectant. It often outperforms fancier molecules in head-to-head hydration tests and shows up in nearly every good moisturizer. If a product has glycerin high on the list, a lot of the hydration is coming from it regardless of what the front label brags about.
- Beta-glucan. Another fermentation-friendly hydrator with soothing and film-forming qualities, popular in calming Korean serums. See our beta-glucan ingredient guide.
- Snail mucin. A multi-component humectant-plus-repair ingredient with its own dedicated following in K-beauty.
- Panthenol (provitamin B5) and ceramides. Humectant and barrier-support roles respectively, often paired with PGA or HA to do the sealing that humectants alone cannot.
The pattern across all of these: humectants pull and hold water, but they need something occlusive (a cream, an oil, a barrier lipid) on top to lock it in. PGA does a bit of that sealing itself, which is part of its appeal, but it is not a full moisturizer.
One more thing the marketing tends to skip: in a finished serum, the humectant on the front of the bottle is rarely doing all the work. A typical hydrating serum is mostly water plus glycerin, with a small percentage of the headline active. So when a PGA serum hydrates well, glycerin and butylene glycol in the same formula are usually pulling their weight too. This is not a knock on PGA. It is a reason to judge a product by how it performs and how the whole formula reads, not by which trendy molecule got top billing. Two serums can both say "polyglutamic acid" on the label and feel completely different because of everything else in the bottle.
Safety and who it's for
Polyglutamic acid has a clean safety reputation. It is the same biopolymer found in natto, it is biodegradable and water-soluble, and reported reactions in cosmetic use are rare and mild. It is generally considered non-comedogenic, so it is unlikely to clog pores or trigger breakouts, which makes it friendly for oily and acne-prone skin. As with any ingredient, sensitive or reactive skin can still react to a finished formula (often to a preservative or fragrance rather than the PGA itself), so patch testing a new product is the sensible move.
For broader safety context on cosmetic ingredients, the Cosmetic Ingredient Review is the standard industry safety-assessment body in the US, and finished K-beauty products sold in Korea pass through Korean cosmetic regulation as well.
Who it's for:
- Dehydrated, dull, or tight skin that wants a dewy finish and a moisture-sealing top layer.
- People who find HA serums feel tight as they dry; PGA's film can feel more comfortable.
- Oily and acne-prone skin that wants hydration without heaviness or clog risk.
- Layering fans building a Korean-style hydration stack who want both HA and PGA.
Who can skip it:
- Anyone on a tight budget or minimalist routine. A good glycerin- and HA-based moisturizer covers most of the same ground for less money and more proven benefit.
- People chasing anti-aging results specifically. The firming and wrinkle claims for PGA are not yet backed by strong human trials. For that goal, retinoids, vitamin C, and sunscreen have far better evidence.
If your main issue is a damaged moisture barrier rather than simple dehydration, the priority shifts toward ceramides and barrier lipids; see our evidence guide to Korean barrier-repair ingredients. And if your goal is that lit-from-within look, our glass skin ingredient stack shows where humectants like PGA fit alongside the rest.
How to use it
Polyglutamic acid is a humectant, so the same rule applies as for hyaluronic acid: apply it to slightly damp skin, not bone-dry skin, so it has water to grab. On dry skin in a dry room, a humectant can pull moisture out of deeper layers instead of holding it in.
A simple, evidence-sensible order:
- Cleanse.
- Apply a hydrating toner or essence to leave skin damp.
- (Optional) Hyaluronic acid serum to draw water in.
- Polyglutamic acid serum or essence on top to help hold it.
- Moisturizer or cream to seal.
- Sunscreen in the morning.
You do not need both HA and PGA to benefit. Either one over damp skin, sealed with a moisturizer, does the core job. The two-step layering is a refinement, not a requirement.
A few practical notes. PGA serums often feel slightly tacky as they set, which is the film forming; that is normal and usually disappears once your moisturizer goes on. Concentrations in cosmetics are typically very low (often well under 1%), so more product is not automatically better; a thin, even layer is enough. PGA pairs fine with most actives, including niacinamide, peptides, and exfoliating acids, because it is chemically inert and just sits on the surface. If you use a strong retinoid or acid that leaves skin sensitized, a humectant layer like PGA underneath your moisturizer can make the routine feel more comfortable. And in a dry climate or an air-conditioned room, always seal a humectant with a cream; on its own in dry air, any humectant can work against you by pulling water from deeper skin to the surface where it evaporates.
Bottom line
Polyglutamic acid is a real, effective, food-derived humectant that earns its spot in Korean hydration routines, especially for a fast dewy finish and a moisture-sealing top layer. The eye-catching "holds 4x more water than hyaluronic acid" claim is a true in-vitro number that does not reliably translate to your skin, and the deeper anti-aging and barrier claims are still ahead of the human evidence. Hyaluronic acid remains the better-proven all-around hydrator. The smartest move is not choosing between them but using each where it shines.
Frequently Asked Questions
Does polyglutamic acid really hold more water than hyaluronic acid?
In a test tube, yes. Lab assays show very high water-absorption for polyglutamic acid, including the widely quoted "4x more than hyaluronic acid" figure. But those numbers measure the raw material, not your skin. On real faces, hyaluronic acid has the larger and stronger body of human clinical evidence, so it is the better-proven hydrator overall. The lab advantage does not reliably carry over to finished products.
Can I use polyglutamic acid and hyaluronic acid together?
Yes, and it is a common Korean approach. They work on slightly different levels: hyaluronic acid draws water in (and at low molecular weight can reach deeper layers), while polyglutamic acid mostly forms a moisture-holding film on the surface. Apply hyaluronic acid first on damp skin, then polyglutamic acid on top, then a moisturizer to seal. You do not need both to benefit, though.
Is polyglutamic acid safe for acne-prone or sensitive skin?
It has a clean safety record and is generally considered non-comedogenic, so it is unlikely to clog pores or cause breakouts, which makes it a reasonable choice for oily and acne-prone skin. Reactions are rare and usually trace to other ingredients in the formula rather than the polyglutamic acid itself. Sensitive skin should still patch test any new product before applying it to the whole face.
Does polyglutamic acid help with wrinkles and anti-aging?
The evidence is not strong enough to promise this. Some cell-based and extract studies hint at barrier and wrinkle benefits, but there are no large, well-controlled human trials confirming polyglutamic acid as an anti-aging active. If wrinkles are your main concern, ingredients like retinoids, vitamin C, and daily sunscreen have far better-established results.
What's the difference between polyglutamic acid and sodium polyglutamate?
Sodium polyglutamate is the sodium-salt form of polyglutamic acid. It is more water-soluble and stable, which is why it appears in many formulas, but it behaves as the same humectant ingredient on skin. On a label, "Polyglutamic Acid," "Sodium Polyglutamate," and "Natto Gum" all point to the same fermentation-derived biopolymer.
This article is for general educational purposes only and is not medical advice. Consult a dermatologist or qualified healthcare professional for concerns about your skin.