Polyglutamic Acid

Amino acid polymer that holds water for plump, hydrated skin.

Also known as: Poly-L-glutamic acid, γ-polyglutamic acid, PGA; same name.

What it is

Polyglutamic acid is a naturally occurring amino acid polymer—a chain of glutamic acid molecules—that functions as a humectant. It's derived from fermentation (often from Bacillus subtilis) and is structurally similar to hyaluronic acid in its water-binding capacity.

What it does

PGA attracts and binds water molecules to the skin surface and within the stratum corneum, creating a plumping effect and improving skin hydration. It forms a lightweight hydrating film that enhances skin firmness and smoothness without the occlusive feel of heavier moisturizers. Its humectant action helps maintain skin's moisture barrier and can improve the appearance of fine lines.

The evidence

Moderate evidence supports PGA's hydrating efficacy; studies show it can hold up to 5,000 times its weight in water and improve skin hydration and elasticity comparable to hyaluronic acid. Evidence is strongest for short-term hydration and plumping; long-term barrier repair data are more limited.

Best for

Dehydrated, dull, and aging skin; those seeking lightweight hydration without heaviness; all skin types including oily and sensitive.

Pairs well with

Hyaluronic acid, glycerin, niacinamide, ceramides, peptides, and antioxidants like vitamin C for synergistic hydration and barrier support.

Use cautiously with

No major conflicts; pairs well with most actives. In very dry climates, ensure occlusive layer (oil or cream) follows to prevent transepidermal water loss.

Cautions

Generally well-tolerated and non-irritating; rare sensitivity in extremely sensitive skin. No sun-sensitivity, pregnancy concerns, or prescription interactions noted.