What does polyglutamic acid do for skin?

What is polyglutamic acid?

Polyglutamic acid is a large, water soluble molecule made from linked units of glutamic acid. It can be produced through bacterial fermentation and is found in fermented foods such as natto. In skincare, its useful feature is the moisture retaining layer it creates when applied to skin. The skin's outer layer normally conserves water and protects against outside irritants, so reducing water loss is a practical part of keeping skin hydrated.1

Does it strengthen the skin barrier?

Barrier support is promising, but its long term benefits on human skin remain uncertain. In laboratory skin cells, a particular form of polyglutamic acid increased activity linked to barrier proteins and hyaluronic acid production. In reconstructed skin, a 1% application increased several markers involved in barrier function and hydration. Those findings make hydration and barrier support reasonable areas of interest, not a reason to use a serum as treatment for a skin disease. The 1% laboratory concentration is not a recommended strength for your routine.1

Is polyglutamic acid a good moisturizer?

Polyglutamic acid is useful as a moisturizing ingredient, but a hydrating serum and a complete moisturizer do different jobs. Moisturizers commonly combine humectants, which attract and retain water, emollients, which soften skin, and occlusives, which reduce water escaping from the surface. A serum can add hydration without supplying the richer texture that very dry skin needs. Keep the moisturizer in the routine; a serum does not get promoted just because its name is longer.3

Choose the moisturizer around the severity of your dryness. Creams contain more oil and are more hydrating than lotions or gels, while ointments provide the strongest protection against water loss. A lighter gel can be more suitable for oily skin. Combination skin can need moisturizer on dry areas without the same amount on oily areas. A hydrating serum is an optional addition to a good moisturizing routine, not an admission fee for having one.4

How do you use polyglutamic acid serum?

Follow your serum's directions for quantity and frequency. As a practical example, The INKEY List Polyglutamic Acid Serum can be used morning and evening as the last serum before moisturizer.5

1. 1Cleanse your face.
2. 2Apply your other hydrating serum first, if you use one. Layer serums from the thinnest texture to the thickest.
3. 3For The INKEY List serum, pat a pea sized amount into your face and neck. Avoid the eyes.
4. 4Follow with moisturizer.
5. 5In the morning, finish with sunscreen. Choose broad spectrum protection, water resistance and an SPF of at least 30.

For dry skin, applying moisturizer while skin is still damp helps trap existing water. That is general moisturizing advice, not a requirement to soak your face before every serum. Creams and ointments also spread more easily on damp skin. After bathing, moisturize promptly rather than waiting until the skin has dried completely.4

Can you use it with hyaluronic acid or other actives?

You can pair the two hydrating serums. The INKEY List tells you to apply its Hyaluronic Acid Serum first, then its Polyglutamic Acid Serum to help retain hydration. The brand also allows its polyglutamic acid serum alongside exfoliating acids and retinol. Compatibility does not mean you need every product in the same routine: if dry winter skin is already struggling with exfoliating products, moisturizing rather than adding more exfoliation is the useful move.245

What should you expect, and how quickly?

The INKEY List describes an immediately hydrated, plumped feel after applying its serum, with fuller results taking up to six weeks of consistent use. Treat that as the brand's timeframe for its formula, not a deadline for every polyglutamic acid product. The useful early change is hydration and surface smoothness. An instantly softened appearance of fine lines is different from lasting wrinkle correction. Do not increase the amount or frequency to chase faster results; overuse can cause irritation and sensitivity.25

The INKEY List also suggests its serum as a makeup primer or mixing a pea sized drop into foundation for a glowing finish. That is an option for this formula, not a necessary hydration step. The same serum can serve as makeup prep, which at least gives one bottle a second job instead of adding another bottle.2

Is polyglutamic acid good for dry skin?

Its moisture retaining action makes polyglutamic acid a useful option for dry skin, but the rest of the routine matters. Dry skin lacks moisture in its outer layer and can become rough, scaly or cracked. Moisturizers remain the mainstay of care, with thicker products generally more appropriate as dryness increases. Choose something you tolerate and can use regularly; texture, cost and availability matter more than collecting a particular ingredient.17

Cold outdoor air and heated indoor air can disrupt the skin barrier, so a light lotion that works in warmer weather can become insufficient in winter. A cream, oil or balm can be a better fit. Use a gentle, moisturizing cleanser rather than one that leaves skin drier. Short, lukewarm showers and replacing standard soap with a gentler substitute also help remove avoidable causes of dryness.67

Can polyglutamic acid irritate skin?

A polyglutamic acid product can still irritate skin. Moisturizing formulas can cause burning or stinging in sensitive skin, and preservatives or fragrances can trigger contact allergy in susceptible people. Contact dermatitis means an inflamed skin reaction after contact with a substance. Stop the product if contact dermatitis develops. A sensitive skin label does not remove the need to pay attention to a reaction.3

The INKEY List labels its serum suitable for sensitive skin, pregnancy and breastfeeding, and recommends patch testing before adding it. Those suitability statements belong to that product, not every formula containing polyglutamic acid. If you use prescription skincare, the brand tells you to check with your doctor before combining products.5

If dryness does not improve with a moisturizing routine, or becomes painful, cracked, bleeding, stinging or very irritating, make an appointment with a dermatologist. Persistent symptoms need more than another hydrating serum, and a prescription or a change to your home routine could be needed.4