Polyglutamic Acid vs Hyaluronic Acid: The Hydration Research Compared
By Dr. Mei Chen · Cosmetic Dermatologist & Senior Editor, The Exosome Edit
Updated Jun 2026- PGA is a fermented biopolymer; HA is a sugar chain your body already makes.
Last updated: June 2026
Quick Answer
- PGA is a fermented biopolymer; HA is a sugar chain your body already makes.
- Lab data shows PGA holds more water and resists evaporation longer than HA.
- PGA forms a surface film; HA pulls water into the skin's deeper layers.
- Layer HA first, then PGA on top, to seal in the water HA attracts.
Medical and patch-test disclaimer: This article is for education only. It is not medical advice and does not replace a consultation with a board-certified dermatologist. Both polyglutamic acid and hyaluronic acid are generally well tolerated, but any new product can irritate sensitive or compromised skin. Patch-test on your inner forearm for 48 hours before applying to your face, and stop use if you notice redness, stinging, or itching. If you have a medical skin condition, talk to a clinician first.
Affiliate disclosure: The Exosome Edit may earn a small commission when readers buy through links in this article, at no extra cost to you.
Hyaluronic acid has owned the hydration aisle for two decades. Walk into any pharmacy and you'll find a dozen HA serums. But a quieter ingredient keeps showing up on labels now: polyglutamic acid, usually written as PGA.
Most shoppers can't say how the two differ. The marketing claims fly around — "ten times more hydrating," "five thousand times its weight in water" — with no study attached. So we pulled the actual research and read it.
This is the honest comparison. We'll show you what the lab data says, where it's strong, and where it's thin. Because the PGA literature is real, but it's much smaller than HA's, and we'll be clear about that throughout.
Is polyglutamic acid better than hyaluronic acid?
Neither one is simply "better" — they hydrate by different routes and work best together. Lab studies suggest PGA holds more water per gram and forms a longer-lasting surface film, while HA is the more deeply studied humectant that draws water into the skin. For most people the smart move is to use both, not to pick a winner.
The "better" framing comes from product marketing, not from head-to-head human trials. There simply aren't large clinical studies pitting the two against each other on real faces. So treat the comparison as complementary chemistry, not a contest.
What is polyglutamic acid and where does it come from? (Bacillus natto fermentation)
Polyglutamic acid is a peptide-like polymer made of many glutamic acid units linked in a chain. The skincare form is gamma-PGA (γ-PGA), and it is not synthetic. It comes from bacterial fermentation, most famously from Bacillus subtilis — the same microbe behind natto, the sticky fermented soybean dish from Japan.
That sticky, stringy texture of natto? That's γ-PGA. Manufacturers grow the bacteria in tanks, then purify the polymer out of the broth. A 2024 review in Frontiers in Microbiology identifies Bacillus subtilis (natto) ATCC 15245 as a glutamic-acid-dependent producer strain used for this purpose (Elbanna et al., 2024).
So PGA is a fermentation biopolymer with a long food-safety history. HA, by contrast, is a glycosaminoglycan — a sugar-based molecule your own skin, joints, and eyes produce naturally. One is a fermented protein-like chain. The other is a native sugar chain. Different families entirely.
That difference matters for how each one is sourced and priced. Cosmetic HA is also made by bacterial fermentation now, but the process has been industrialized for decades, so supply is huge and cheap. PGA production is younger and runs at smaller scale. A 2022 review in Foods notes that Bacillus subtilis is the best-characterized γ-PGA producer and a "GRAS" (generally recognized as safe) organism, which is reassuring on the safety front (Chen et al., 2022).
How does polyglutamic acid hydrate vs hyaluronic acid? (mechanism, water-holding capacity)
The two work in different zones. HA is a humectant that binds water and pulls it toward the skin, and smaller HA fragments travel into deeper layers. PGA mostly stays near the surface, where it forms a thin, water-swollen film that traps moisture and slows evaporation.
Think of it as a two-step system. HA brings the water. PGA helps hold it there.
On raw water-holding capacity, the lab numbers favor PGA. A 2014 study in the Saudi Journal of Biological Sciences measured γ-PGA from Bacillus subtilis D7 at 86.8% hygroscopicity after 72 hours at high humidity, with water-holding capacity still at 56.9% after nine days (Lee et al., 2014). The authors note prior research found γ-PGA's moisturizing effect exceeded both collagen and hyaluronic acid.
You've probably seen the "5,000 times its weight in water" claim for PGA. Be skeptical. Those figures come from supplier marketing, not peer-reviewed human data, and they describe ideal lab conditions, not your face. The reliable takeaway is simpler: PGA is strongly hygroscopic and forms a film, which is a real, documented advantage for surface moisture retention.
A 2023 review in Materials explains the film mechanism. Hydrogen bonds in γ-PGA give it "excellent water absorption properties," which is also why it's studied for wound dressings that need to stay moist (Cai et al., 2023).
HA's mechanism is different in a useful way. Because HA exists in many molecular sizes, formulators blend them: large molecules sit on the surface and plump, while smaller fragments slip into deeper layers to hydrate from within. PGA doesn't really do that deeper-layer trick — it's a surface specialist. So one reaches down, the other guards the top.
This is exactly why the "which is better" question misses the point. A surface film with no water underneath it dries out fast. Water drawn into the skin with nothing sealing the top evaporates. Used alone, each ingredient leaves a gap the other fills.
The attribute comparison
Here's how the two stack up on the properties that matter for hydration. Sources are cited in the sections above and below.
| Attribute | Polyglutamic acid (γ-PGA) | Hyaluronic acid (HA) |
|---|---|---|
| Chemical family | Fermented peptide-like polymer (glutamic acid chain) | Glycosaminoglycan (sugar chain) |
| Source | Bacillus subtilis / natto fermentation | Native to human skin; made by bacterial fermentation for cosmetics |
| Where it acts | Mostly skin surface (film) | Surface plus deeper layers (smaller fragments) |
| Water-holding (lab) | Very high; ~57% held after 9 days in one study | High; the long-standing humectant benchmark |
| Film-forming | Yes — forms an occlusive, water-swollen film | Minimal film; works as a humectant |
| Molecular weight | ~10–2,000 kDa typical (strain-dependent) | ~5 kDa to >1,000 kDa depending on grade |
| Cost | Higher (newer, smaller supply) | Lower (mature, large-scale supply) |
| Depth of research | Thinner; mostly in vitro and lab models | Extensive; decades of clinical data |
Does polyglutamic acid inhibit hyaluronidase / boost natural HA?
This is PGA's most interesting trick, and it has lab support. Hyaluronidase is the enzyme that breaks down your skin's own hyaluronic acid. By slowing that enzyme, PGA may help your skin hold onto the HA it already makes.
A patent from BioLeaders Corp reported that γ-PGA inhibited hyaluronidase with an IC50 around 0.0025%, reaching roughly 100% inhibition at 0.008% — and the effect held across molecular weights from 50 to 4,000 kDa (Sung et al., US8916141B2, 2014). Note this is patent data, not an independent peer-reviewed trial, so weigh it accordingly.
There's also evidence PGA may nudge your skin to make more of its own HA. In a 2025 study in the International Journal of Molecular Sciences, γ-PGA applied to keratinocytes raised the expression of hyaluronic acid synthase genes (HAS-1, HAS-2, HAS-3) in a dose-dependent way, alongside aquaporin 3, a water-channel protein (Ko et al., 2025). That same study also lifted barrier proteins like filaggrin, involucrin, and loricrin.
One caveat the authors state plainly: that work was done in cells and a reconstructed skin model, not on human volunteers. So the HA-boosting story is promising but not yet proven on real skin. If barrier health is your focus, our dermatologist barrier repair routine covers the broader picture.
Should you layer polyglutamic acid and hyaluronic acid together?
Yes — and the order matters. Apply your hyaluronic acid first, onto damp skin, so it can draw water in. Then layer polyglutamic acid on top to form a film that locks that water against evaporation. They cover different jobs, so stacking them is logical rather than redundant.
The pairing has a mechanistic rationale beyond just "two humectants." PGA's hyaluronidase inhibition may slow the breakdown of the HA you just applied (and the HA your skin makes), which is why some formulators combine them deliberately.
A simple layering routine looks like this:
- Cleanse and leave skin slightly damp.
- Apply hyaluronic acid serum; press in.
- Apply polyglutamic acid serum on top.
- Seal with a moisturizer to reinforce the barrier.
- Use sunscreen every morning.
If you stack PGA with stronger actives like retinoids, sequencing gets trickier — our retinoids and actives research guide walks through how to layer without irritation. And if your skin runs sensitive, start slow and review our routines for sensitive skin before piling on products.
What does the clinical evidence show for polyglutamic acid?
Here's the honest answer: the evidence for PGA is real but early. Most of it sits in test tubes, isolated skin cells, and reconstructed skin models — not large human trials. HA, by comparison, has decades of clinical studies behind it. So PGA is a promising ingredient with a thinner evidence base, and anyone telling you it's "clinically proven superior" is overstating the data.
What we do have is consistent and pointing in one direction. The table below summarizes the strongest published findings.
What the studies actually found
| Study (year) | Model | Key outcome |
|---|---|---|
| Ko et al., 2025 (IJMS) | Keratinocytes + reconstructed skin | γ-PGA raised HAS-1/2/3, aquaporin 3, filaggrin, involucrin, loricrin |
| Lee et al., 2014 (Saudi J Biol Sci) | In vitro hygroscopicity test | 86.8% hygroscopicity at 72h; 56.9% water-holding at 9 days |
| Sung et al., 2014 (US patent) | In vitro enzyme assay | Hyaluronidase IC50 ~0.0025%; ~100% inhibition at 0.008% |
| Cai et al., 2023 (Materials) | Materials review | Strong water absorption via hydrogen bonding; film/wound-dressing use |
| Elbanna et al., 2024 (Front Microbiol) | Review | γ-PGA reduces TEWL, forms protective films, acts as "super moisturizer" |
The gap in the table is obvious: no large, randomized, controlled trials on human faces measuring hydration over weeks. That study still needs to be done. Until then, treat PGA as a well-supported lab-stage hydrator, not a clinically proven HA replacement.
You can browse the broader PubMed record on this ingredient at PubMed: poly-gamma-glutamic acid skin.
What concentration and molecular weight of PGA matters?
Most cosmetic PGA serums use it at roughly 0.1% to 2%, and you rarely need more than that — it's a high-performance film-former at low doses. Molecular weight ranges widely, generally from about 10 kDa up to 2,000 kDa, and the size changes how it behaves on skin (Chen et al., 2022, Foods).
Bigger isn't automatically better. Higher-molecular-weight PGA forms a stronger surface film and is better at cutting evaporation. Lower-molecular-weight PGA is lighter and may penetrate a bit more. Many formulas blend grades, just as HA serums do.
One reassuring point from the research: the hyaluronidase-blocking effect held steady across a wide molecular-weight range in the BioLeaders data, so you don't need a specific "magic" size to get that benefit. Concentration and formula quality matter more than chasing a single molecular weight on the label.
It's also worth knowing that some labs can now make extremely high-molecular-weight γ-PGA. The 2025 IJMS study used a Bacillus subtilis strain producing a polymer near 6,975 kDa — described as the largest reported to date. Whether that translates to better real-world hydration than mid-weight grades is still untested on human skin.
A practical buying tip: don't over-index on the number on the label. Look instead for a serum that pairs PGA with hyaluronic acid and a supporting humectant or two, since the layered formula tends to outperform any single ingredient at a flashy concentration.
For context on how newer regenerative hydrators compare, see our salmon DNA PDRN vs exosomes showdown.
Frequently Asked Questions
Is polyglutamic acid safe for sensitive skin? PGA is generally well tolerated and non-irritating because it works mostly on the skin surface as a film-former. Still, any product can cause a reaction, so patch-test for 48 hours before facial use. People with very reactive skin should introduce it slowly.
Can I use polyglutamic acid every day? Yes, most people can use PGA morning and night. It pairs well with hyaluronic acid, niacinamide, and most moisturizers. If you use strong actives like retinoids, watch for any irritation and space products out.
Does polyglutamic acid replace hyaluronic acid? No. They hydrate by different mechanisms — HA draws water in, PGA seals it at the surface — so they complement each other rather than substitute. The research supports layering both, not dropping one.
Why is polyglutamic acid more expensive than hyaluronic acid? PGA is newer to skincare and produced at smaller scale, while HA has a mature, high-volume supply chain. Lower supply and demand pricing make PGA serums cost more per bottle, though formula concentration also drives price.
Is the "5,000 times its weight in water" claim for PGA true? That figure comes from supplier marketing under ideal lab conditions, not peer-reviewed human data. Published studies confirm PGA is strongly hygroscopic and film-forming, but treat the giant multiplier claims with caution.
Related Reading
- A dermatologist barrier repair routine
- Best niacinamide serums with clinical evidence
- Retinoids and actives: the complete research-based guide
-- The Exosome Edit Team