What is Polyglutamic Acid?

Polyglutamic Acid, often shortened to PGA, is a large, naturally derived molecule made of repeating units of the amino acid glutamic acid. It is typically produced through the fermentation of soybeans or other substrates by specific bacteria. In skincare, PGA is valued as a humectant and film-forming ingredient, meaning it both attracts water and forms a thin, moisture-trapping layer on the surface of skin.

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How Does It Work?

Because Polyglutamic Acid is a large molecule, it doesn't penetrate deep into skin the way some smaller ingredients do. Instead, it works mainly on the surface, where it forms what's sometimes described as a microgel, a very thin film that swells slightly when it contacts water and traps that moisture against the skin. This film also helps reduce how quickly water evaporates from the skin's surface over the course of the day.

Because of its surface-level, film-forming action, Polyglutamic Acid is often paired in formulas with lower molecular weight humectants, such as smaller forms of hyaluronic acid, which can support hydration a bit further into the upper layers of skin. Used together, the idea is to address both surface-level moisture retention and slightly deeper hydration in the same routine. Some early research has also suggested PGA may help slow the breakdown of hyaluronic acid already present in skin, though this is a newer area of study.

Transparency note: You'll often see Polyglutamic Acid marketed with striking statistics, such as holding thousands of times its own weight in water, or being described as more hydrating than hyaluronic acid. These specific figures are widely repeated in industry and brand sources, but robust, independent, head-to-head clinical comparisons against hyaluronic acid in finished skincare products are limited. It's reasonable to treat Polyglutamic Acid as a genuinely useful, well-tolerated humectant, without assuming the boldest marketing claims about it are settled science.