Ingredient Encyclopedia · P
INCI: Polyglutamic Acid
Polyglutamic acid is a moisture-retaining powerhouse that has been overshadowed by hyaluronic acid—unfairly so. This fermented biopolymer binds water to the skin’s surface and forms a wafer-thin film over the skin, which noticeably retains moisture for longer. Research on this ingredient is still in its early stages, but the initial data are promising.
What is polyglutamic acid?
Polyglutamic acid (PGA) is a biopolymer composed of many linked units of the amino acid glutamic acid. It is usually produced through fermentation with Bacillus subtilis—the same bacterium used to make the traditional Japanese dish natto. In skincare, PGA acts as a humectant: it attracts water and locks it in.
The key difference from hyaluronic acid is that PGA molecules are large and do not penetrate the skin at all. Instead, they form a fine, invisible film on the skin’s surface that binds water there and slows evaporation. Hyaluronic acid—depending on its molecular size—also works in the upper layers of the skin. So the two do not compete; they complement each other: hyaluronic acid plumps the skin, while PGA seals the surface. In laboratory comparisons, PGA is also credited with a very high water-binding capacity.
Effect: What’s Been Proven
Honesty is called for here: The body of research on PGA is significantly smaller than that on hyaluronic acid—hence only two out of five bars. There is laboratory data on its pronounced water-binding capacity and a few small studies showing improved skin hydration and elasticity after application. Large, independent clinical studies are still lacking. What can be said with confidence: PGA has been proven to work as a humectant, and the immediate effect—a smoother, plumper skin surface—is clearly noticeable. As of now, broader long-term claims remain unsubstantiated.
Application & Combination
PGA fits into your morning and evening routine: apply it to slightly damp skin after cleansing, then follow with a cream. When combined with hyaluronic acid, use the following order: hyaluronic acid first, then PGA on top—this way, the film locks in the moisture from both active ingredients.
Pairs well with
✓ Hyaluronic acid—the duo: plumps from the inside, seals from the outside
✓ Niacinamide & Ceramides – hydration plus barrier reinforcement
✓ Rich creams as the final step—further slow down evaporation
Note
! Research is still in its early stages—promising, but less studied than hyaluronic acid
! The film-forming effect may feel heavy on very oily skin—test it in the evening first
Polyglutamic acid in the BONSANA lineup
Available directly in the shop
Moisturizing Serums in the BONSANA Shop
Polyglutamic Acid, Hyaluronic Acid & More – Face Serums for Every Skin Type, shipped from our warehouse in Switzerland.
View facial serums →Frequently Asked Questions About Polyglutamic Acid
Is polyglutamic acid better than hyaluronic acid?
Neither—they work in different ways. Hyaluronic acid hydrates even the upper layers of the skin, while PGA forms a film on the surface and locks moisture in. When combined, they complement each other perfectly.
Does polyglutamic acid penetrate the skin?
No, the molecules are too large for that. PGA acts as a moisture-retaining film on the skin’s surface—and that’s exactly what makes it effective: it slows evaporation and keeps the skin supple longer.
What skin types is PGA suitable for?
Generally, it’s suitable for all skin types, especially dry and dehydrated skin that feels tight. On very oily skin, the film may feel heavy—in that case, test the product in the evening first.
How do I apply a PGA serum correctly?
Apply to slightly damp skin after cleansing; a hyaluronic acid serum can be applied underneath. Finish with a cream to lock in the moisture.
