Polyglutamic Acid vs Hyaluronic Acid: Two Humectants Compared

Polyglutamic acid is a water-binding chain of amino acids made by bacteria, the same polymer found in natto. Like hyaluronic acid, it works as a humectant at the skin surface. Unlike hyaluronic acid, it has almost no human skin trials behind it. This guide covers what it is, how it differs, which popular claims we could not verify, and one allergy link worth knowing.

What is polyglutamic acid?

Polyglutamic acid, usually written γ-PGA in research papers, is a chain of glutamic acid units. A 2015 review describes it as a naturally occurring biopolymer built from L-glutamic acid, D-glutamic acid, or both. Its properties vary with its shape, its mix of those two forms, and its molecular mass. The review describes it as biodegradable and non-toxic. Outside skincare, it is used in food, medicine and wastewater treatment.

Bacteria make it. Natto, the Japanese fermented soybean dish, is fermented by Bacillus subtilis and contains γ-polyglutamic acid. Commercial production relies on bacteria too, and the 2015 review notes the search for higher-yield strains is still going. A 2024 study, for example, grew Bacillus subtilis natto on seaweed to make it for cream formulations.

The "gamma" matters. The glutamic acid units are joined through an unusual bond. As a result, γ-PGA is not susceptible to proteases, the enzymes that break down ordinary proteins. It is an amino acid polymer that does not behave like a typical protein.

On an ingredient list you may see polyglutamic acid or its salt, sodium polyglutamate. Research creams have used it at 0.2 to 2 percent. Brands rarely state the percentage or the molecular weight.

How polyglutamic acid differs from hyaluronic acid

The two get compared because they do the same basic job: they bind water. Chemically they belong to different families. In practice they sit in the same place.

Hyaluronic acid is a sugar-based chain, a glycosaminoglycan, and your skin makes it. A 2012 review calls it the key molecule involved in skin moisture, with a unique capacity for retaining water. Polyglutamic acid is an amino acid chain produced by microbes. Both chains carry many acid groups, a feature a 2024 study notes for each polymer (2024 formulation study).

	Polyglutamic acid	Hyaluronic acid
Backbone	Glutamic acid, an amino acid	Sugar units, a glycosaminoglycan
Made by	Bacteria, including Bacillus subtilis	Your own skin, which produces it naturally
Job in a formula	Humectant	Humectant
Where the evidence comes from	Lab tests, cell cultures, one reconstructed skin model	Lab work plus vehicle-controlled human trials
Randomized trials on human skin we found	None	Yes

Size explains why. A widely cited paper put the upper limit for skin absorption at 500 daltons. A single glutamic acid unit weighs about 147 daltons on its own, so a chain of just a few units already passes that line. The γ-PGA tested in recent cell work was high molecular weight. Like large hyaluronic acid, it is a surface ingredient.

What the polyglutamic acid research actually shows

Start with the lab. A 2024 study compared commercial γ-PGA with hyaluronic acid and glycerin in laboratory testing. It found a comparable hydration effect across the three. Seaweed-grown γ-PGA showed greater hydration capacity in the same work. Creams made with it did not harm cultured keratinocytes.

One detail from that study needs a warning label. The seaweed-derived creams absorbed some ultraviolet light in laboratory readings. That is a property of a test formula, not sun protection. Nothing here replaces a broad-spectrum sunscreen.

Then cells. A 2025 study isolated a new Bacillus subtilis strain from a wetland on Jeju Island, Korea, and proposed it for commercial production. The team tested its high molecular weight γ-PGA on keratinocytes. It raised gene activity for barrier proteins, including filaggrin, involucrin and loricrin. It raised activity for enzymes that make skin lipids too. It also increased hyaluronic acid synthase genes and aquaporin 3, a water channel involved in skin hydration. On a reconstructed skin model, a 1 percent topical dose raised filaggrin, involucrin, CD44 and aquaporin 3 (2025 study).

That is interesting, and still a long way from a face. Cell and tissue models are a first step, not a result on skin you live in. The authors themselves call for further research on long-term effects.

Then people. We could not find a single randomized trial of topical polyglutamic acid on human skin in PubMed. Hyaluronic acid has them. In one, 76 women aged 30 to 60 applied a 0.1 percent hyaluronic acid cream around one eye. A vehicle cream went around the other, twice daily for 60 days. Every hyaluronic acid version improved hydration and elasticity against the vehicle.

That trial tested five molecular weights. The size question is its own topic, covered in hyaluronic acid and molecular weight, so we will not repeat it here.

Does polyglutamic acid hold more water than hyaluronic acid?

This is the claim most product pages lead with. Polyglutamic acid is often said to hold several thousand times its weight in water, several times more than hyaluronic acid.

We could not find a peer-reviewed measurement of those multiples for polyglutamic acid in a skincare formula. The big numbers may come from materials science. A 2004 study turned a polyglutamic acid solution into a gel with gamma irradiation, and at one dose the dried gel absorbed about 3,500 times its own weight in water. That is a cross-linked lab material, not a serum on skin. The closest skincare data we found is the 2024 lab comparison above. It reported a comparable hydration effect between commercial γ-PGA and hyaluronic acid, not a multiple. Treat any "times its weight" figure on a label as marketing until the brand publishes its method.

The ratio also misses the practical point. A humectant draws water from wherever water is available. A 2016 dermatology review calls humectants a double-edged weapon. They pull water from the dermis into the epidermis, where it is easily lost to the air. That is why the review says they are usually combined with an occlusive.

More binding capacity does not change that physics. The fix is the same for both ingredients. Apply them to damp skin, then seal with a moisturizer. That is the method behind skin flooding.

Claims about polyglutamic acid we could not verify

• "It protects your hyaluronic acid." Some copy says polyglutamic acid slows the enzyme that breaks hyaluronic acid down. We found no human skin study testing that. The 2025 cell study measured more hyaluronic acid synthase activity, which concerns making it, not preserving it.
• "It beats hyaluronic acid." We found no head-to-head trial on human skin.
• "It firms skin." We found no human data for firmness.
• "It cannot cause allergy." The 2015 review does describe γ-PGA as non-immunogenic. The allergy data below complicate that.

Can you be allergic to polyglutamic acid?

Yes, and the route is unusual. Polyglutamic acid is an allergen in natto that causes late-onset anaphylaxis. In a 2018 study of 140 food allergy outpatients, all 13 with natto allergy tested positive to polyglutamic acid. Of those 13, 92.3 percent had a marine sports hobby, and 84.6 percent surfed. How much natto people ate made no significant difference to sensitization.

That pointed the researchers away from the diet and toward the skin. Jellyfish stings contain polyglutamic acid. Repeated stings may sensitize people through the skin, and the reaction later shows up when they eat natto. An earlier case report raised the same possibility of skin sensitization from jellyfish stings.

What this means for skincare is unknown. A sting pierces the skin, which is not the same as a serum on intact skin. We found no published reports of allergy to polyglutamic acid skincare. If you have a natto or jellyfish allergy, ask an allergist before using it.

How to use polyglutamic acid and hyaluronic acid

Both are water-based humectants, so they go early in a routine. Apply them after cleansing and before creams. The general rule is thinnest to thickest, set out in our skincare routine order guide.

• Apply either one to damp skin.
• Follow with a moisturizer or an occlusive to slow evaporation.
• Using both is fine. We found no evidence of a benefit from combining them, and none of harm.
• Choose on texture, price and tolerance. Neither has shown a clear advantage on human skin.

Both large polymers work mainly in the outer layer. That is where surface hydration happens, and it is a legitimate reason to use them. It is also where their evidence ends. Our explainer on the stratum corneum covers why that layer is so hard to get past. For a compromised barrier, humectants are one part of the repair routine, not the whole of it.

Frequently asked questions

Is polyglutamic acid better than hyaluronic acid?

Not on the current evidence. In lab testing, commercial polyglutamic acid showed a hydration effect comparable to hyaluronic acid. Hyaluronic acid has randomized human trials, and we found none for polyglutamic acid. Pick on texture and tolerance, not on a water-weight multiple.

Can you use polyglutamic acid and hyaluronic acid together?

Yes. Both are water-based humectants, and nothing in the research we reviewed suggests a conflict. There is also no published evidence that the pair works better than either alone. Apply them to damp skin and seal with a moisturizer.

Does polyglutamic acid really hold 5,000 times its weight in water?

We could not find a peer-reviewed measurement supporting that figure for polyglutamic acid in skincare. The one lab comparison we found reported hydration comparable to hyaluronic acid, not several times greater. On skin, what matters more is whether the water stays, which depends on humidity and on sealing it in.

What is polyglutamic acid made from?

It is a chain of glutamic acid units produced by bacteria, including Bacillus subtilis, the organism used to ferment natto. Commercial supplies also come from bacterial production. Its properties, including molecular mass, vary with the strain and the process.

Is polyglutamic acid safe for sensitive skin?

Lab work found no harm to cultured skin cells, and we found no reports of reactions to skincare containing it. It is, however, a documented food allergen in natto, possibly through skin sensitization from jellyfish stings. If you have a natto allergy, ask an allergist first. Otherwise, patch test it as you would any new product.

Where does polyglutamic acid go in a routine?

After cleansing and any watery toner, before creams and oils. Apply it to damp skin, then seal it with a moisturizer. In the morning, sunscreen still goes last.