Polyglutamic acid in hair care.

The polyglutamic acid is an active ingredient derived from the polymerisation of glutamic acid, which is obtained from the fermentation of soybean seeds. It is the main component of nattō, a Japanese dish made with fermented soybean seeds. However, the benefits of polyglutamic acid extend beyond the culinary field and into the cosmetic industry, where this active ingredient is particularly valued for its hydrating properties. This characteristic, appreciated by dehydrated skin, can also be beneficial for scalp care.

Polyglutamic acid could potentially hydrate the scalp.

Indeed, like the rest of the skin, the scalp can be subject to moisture imbalances, for instance due to frequent washing or sudden temperature changes. These imbalances can result in uncomfortable sensations of tightness or discomfort. The polyglutamic acid could help to prevent and alleviate them. This active ingredient stands out for its ability to retain up to 5,000 times its weight in water, making it an excellent humectant. By forming a film on the surface of the epidermis, it limits transepidermal water loss and promotes the maintenance of hydration in the upper layers of the scalp. Moreover, studies have shown that polyglutamic acid contributes to the integrity of the skin barrier by stimulating the production of certain molecules belonging to the natural moisturising factor, such as lactic acid and urocanic acid. As a reminder, the natural moisturising factor, also known as NMF, is a set of hygroscopic molecules that form during epidermal differentiation and whose role is to retain water in the stratum corneum.

Polyglutamic acid could soothe the scalp.

Beyond its hydrating abilities, polyglutamic acid also exhibits intriguing anti-inflammatory effects, particularly for irritated or sensitive scalps. Preclinical studies have shown that this active ingredient can significantly reduce the expression of vascular endothelial growth factor A (VEGF-A) and its receptor VEGFR2, key molecules in the processes of angiogenesis related to chronic inflammation. By decreasing these mediators, polyglutamic acid helps to limit the excessive proliferation of blood vessels and vascular permeability, which are responsible for the redness and swelling observed in inflammatory conditions.

Polyglutamic acid could potentially be a beneficial ingredient for sensitive scalps or those prone to itching or dehydration. However, this hypothesis still needs to be confirmed through clinical studies.

Split ends, dull colour... Hair lengths are particularly vulnerable to the repeated daily aggressions, such as pollution, heat, comb friction or the use of heated appliances. Recognised for its excellent hygroscopic properties, polyglutamic acid could be of real interest for taking care of hair lengths. Indeed, by forming a moisturising film on the surface of hair fibres, it could strengthen the already present hydrolipidic film, which aims to limit water loss and form a barrier between the hair and environmental aggressions. The protective effect of polyglutamic acid could also help to strengthen the resistance of the fibres and prevent the appearance of split ends.

However, it is important to note that, to date, the effects of polyglutamic acid on hair have not been validated by clinical studies. The hypotheses put forward above, although plausible, are based on an extrapolation of the moisturising effects of polyglutamic acid.

In which hair products can one find polyglutamic acid?

The polyglutamic acid is increasingly being incorporated into hair care products targeting fragile lengths or dehydrated scalps. This active ingredient can thus be found in lotions or hair serums formulated to soothe the scalp, or even in shampoos, to counterbalance the drying effects of certain surfactants. Finally, polyglutamic acid is sometimes incorporated into masks, conditioners or serums for the lengths, where it helps to keep them hydrated and protected.

• SUNG M. J. & al. Poly-ɣ-glutamic acid attenuates angiogenesis and inflammation in experimental colitis. Mediators of Inflammation (2013).

• RADECKA I. & al.Poly-γ-glutamic acid: production, properties and applications. Microbiology Society (2015).

• YANG S.-A. & al. Gamma polyglutamic acid (gamma-pga, h form), gamma-polyglutamate hydrogels for use as super moisturizers in cosmetic and personal care products (2019).