Polyhydroxy acids (PHAs) are chemical exfoliants. They belong to a group of acids with a larger molecular size than alpha-hydroxy acids (AHAs) and beta-hydroxy acids (BHAs). Therefore, they penetrate less deeply into the epidermis and are more suitable for sensitive skin or skin with conditions. This article provides all the information you need to know about them.
What you need to know about PHAs.
Summary
Published on July 17, 2024, by Maylis, Chemical Engineer — 7 min of reading
Themes:
What are P.H.A.s?
Poly-hydroxy acids (P.H.A.) are referred to assecond-generation A.H.A. (alpha-hydroxy acids). They work by exfoliating the dead cells accumulated on the skin's surface, to revive the complexion's radiance and tighten the pores. This chemical peeling also helps the ingredients of other skincare products to penetrate more deeply into the layers of the epidermis, enhancing their effectiveness.
The three main P.H.A.s used in cosmetics are presented below:
The gluconolactone or gluconic acid : This is a P.H.A. naturally present in skin cells. This antioxidant effectively combats inflammation.
The galactose : It is also naturally present in the body. Its role is to stimulate the production of collagen.
Thelactobionic acid : This is a derivative of lactose that has a moisturising and soothing effect.
The cosmetic benefits of PHAs.
The PHA are true allies for maintaining and promoting a healthy epidermis. Indeed, these active ingredients have multiple benefits and work on several levels to erase irregularities and revive the radiance of dull and tired complexions:
P.H.A.s are renowned for theirkeratolytic effect. They help to remove dead cells that clog pores and smooth the skin's texture. They work by dissolving intercellular bonds, thus stimulating cellular renewal. This process is called chemical exfoliation. Therefore, they prevent the appearance of blackheads as well as signs of ageing such as wrinkles and fine lines.
Several studies have demonstrated their anti-inflammatory properties. Therefore, P.H.A.s are particularly recommended for taking care of oily skin prone to acne and/or skin showing marks due to post-inflammatory hyperpigmentation.
The P.H.A.s are also moisturising : they capture and retain water in the epidermis and reduce skin dryness by half.
Finally, they combat the phenomenon of glycation, a biological process responsible for the degradation of elastin and collagen, essential proteins of the dermal tissue to maintain firm and elastic skin.
Furthermore, the P.H.A.s are molecules of smaller size than the A.H.A.s (glycolic acid, lactic acid, citric acid...) and B.H.A.s (salicylic acid); thus, they penetrate less deeply into the skin layers, and are generally well tolerated by all skin types, even the most sensitive ones that cannot apply A.H.A.s and/or B.H.A.s.
What are the dangers and contraindications of P.H.A.s?
There is no contraindication. P.H.A.-based treatments can be applied to all skin types, even the most reactive and sensitive ones.
Nevertheless, as it is an acid, we advise you to perform a skin tolerance test before using this active ingredient daily. To do this, apply a few drops of the product to the crook of your arm and wait 24 hours. If you observe no reaction, you can apply the treatment to your face.
Finally, P.H.A.s do not have any contraindications to sun exposure unlike A.H.A.s and B.H.A.s.
In which skincare products can PHA be found?
The P.H.A. are most commonly found in exfoliating serums, toning lotions, cleansing gels, and face masks. Typology has developed three products based on P.H.A. :
The exfoliating cleansing gel with 5% P.H.A. and aloe vera is composed of 98% natural origin ingredients. It unclogs pores, evens out skin tone, and smooths skin texture. It is recommended for dull skin as well as skin prone to blackheads.
The peeling mask is an exfoliating gel that combines the action of A.H.A. and P.H.A. to work at different depths of the epidermis and remove dead cells. The complexion is evened out and the skin texture is smoothed. It is used in the evening, once or twice a week.
The serum anti-marks is enriched with brightening and repairing actives, such as gluconolactone from the P.H.A. category and the extract of Centella asiatica. To fade acne scars, apply a drop locally to the affected areas, in the evening only.
The scalp scrub is a pre-shampoo exfoliating gel, which gently removes dead cells for a healthy and balanced scalp. It offers a dual chemical and mechanical exfoliation: the P.H.A. dissolves dead skin, while stimulating scalp hydration, and the jojoba beads gently exfoliate the scalp and stimulate blood microcirculation.
Sources:
KSENZENKO S. M. & al. The polyhydroxy acid gluconolactone provides protection against ultraviolet radiation in an in vitro model of skin photoaging. Dermatologic Surgery (2004).
HEARING V. J. & al., Applications of hydroxy acids: classification, mechanisms, and photoactivity.Clinical,Cosmetic and Investigational Dermatology (2010).
ROTSZTEJN H. & al. Lactic and lactobionic acids as typically moisturising compounds. International Journal of Dermatology (2019).
