All you need to know about PHAs.

Regarded as the next generation of hydroxyl acids, the PHAs (polyhydroxy acids) stand apart from AHAs (alpha-hydroxy acids) and BHAs (beta-hydroxy acids) by their distinctive chemical structure: they are carboxylic acids bearing two or more hydroxyl (–OH) groups attached to carbon atoms or to a cyclic aliphatic chain, whereas AHAs and BHAs carry only one. Moreover, unlike AHAs, PHAs are larger molecules, which limits their penetration into the epidermis. Their action is therefore more superficial yet also gentler.

The three main PHAs used in cosmetics are:

• Gluconolactone (or gluconic acid): Naturally present in skin cells, gluconolactone is the most popular polyhydroxy acid. In addition to its exfoliating properties, it offers antioxidant activity and anti-inflammatory effects, making it beneficial for redness-prone skin.

• Galactose: This simple sugar is naturally present in the body. In cosmetics, it is prized for its exfoliating benefits as well as its ability to stimulate the regeneration of skin tissue.

• Lactobionic acid: Derived from the oxidation of lactose, it belongs to the subcategory of polyhydroxylated bionic acids (PHBA). Its distinctive sugar-enriched chemical structure renders it a potent humectant: it attracts and retains water in the skin, thus enhancing epidermal hydration.

PHAs are considered safe and well tolerated, even for sensitive skin.

Their distinctive feature lies in their larger molecular size compared to AHAs and BHAs. This structure limits their ability to penetrate deeply into the epidermis, thereby reducing the risk of irritation, stinging, or excessive peeling. That is why polyhydroxy acids represent a particularly interesting alternative for exfoliating sensitive skin. Moreover, unlike AHAs and BHAs, PHAs are not photosensitizing. They can therefore be used without issue in summer or in the morning, but this obviously does not replace the need to apply a sunscreen. Additionally, PHAs can be used during pregnancy or while breastfeeding.

That said, even though these are gentle active ingredients, some people may be sensitive to them and develop slight redness upon contact. Therefore, as a precaution, as with any new active ingredient, we recommend performing a tolerance test on first use. To do this, apply a small amount of product to the inside of your arm and observe the area for 24 hours. In the absence of any reaction (redness, itching, irritation), you can safely proceed with application to your face or scalp.

PHAs are most commonly found in exfoliating serums, toning lotions, cleansing gels, and facial masks. Typology has developed three products incorporating gluconolactone:

• The exfoliating face gel cleanser : With 5% gluconolactone and aloe vera, this formula is made up of 98% naturally derived ingredients. It unclogs pores, evens out skin tone, and smooths skin texture. It is particularly recommended for dull complexions and those prone to blackheads.

• The mask for enlarged pores and blackheads : It combines a 10% AHA complex (glycolic acid, lactic acid, tartaric acid, mandelic acid) and 10% PHA (gluconolactone) to act at different depths of the epidermis and remove dead skin cells. It is used in the evening, once or twice a week, and helps even out skin tone and smooth skin texture.

• The mark-fading serum : Enriched with 14% PHA and also containing Centella asiatica, this serum works to fade acne scars. It should be applied topically to the affected areas, in the evening only.

• The scalp scrub : It is an exfoliating gel to use before shampooing that gently removes dead skin cells for a healthy, rebalanced scalp. It delivers dual chemical and mechanical exfoliation thanks to gluconolactone and jojoba beads.