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Acides poly-hydroxylés (PHA).

What You Need To Know About PHAs

PHAs (poly-hydroxy acids) are chemical exfoliants. They belong to a group of acids with a larger molecular size than AHAs (alpha-hydroxy acids) and BHAs (beta-hydroxy acids). Therefore, they penetrate less deeply into the epidermis and are more suitable for sensitive skin or skin conditions. Find in this article all the information you need to know about them.

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What Are PHAs?

Poly-hydroxy acids (PHAs) are qualified as second-generation alpha-hydroxy acids. They work by exfoliating dead skin cells that have accumulated on the surface of the skin to revive the complexion and tighten pores. This chemical peeling also helps other skin care ingredients penetrate deeper into the skin's layers, improving their effectiveness.

The three main P.H.A.s used in cosmetics are listed below:

  • Gluconolactone or gluconic acid: This is a P.H.A. naturally present in skin cells. This antioxidant fights effectively against inflammation.

  • Galactose: It is also naturally present in the body. Its role is to stimulate the production of collagen.

  • Lactobionic acid: This is a lactose derivative that has a moisturizing and soothing effect.

Cosmetic Benefits of PHA

PHAs are real allies in maintaining and promoting a healthy epidermis. Indeed, these active ingredients have multiple advantages and act on several levels to erase irregularities and revive the radiance of dull and tired complexions:

  • P.H.A. are known for their keratolytic effect. They help to eliminate the dead cells which can block pores and smooth the texture of the skin. They act by dissolving the intercellular links to stimulate cell renewal. This process is called chemical exfoliation. Thus, they prevent the appearance of blackheads and signs of aging such as wrinkles and fine lines. 

  • Several studies have demonstrated their anti-inflammatory properties. Therefore, P.H.A.s are particularly recommended to treat oily skin with a tendency to have acne and/or skins with marks due to post-inflammatory hyperpigmentation.

  • P.H.A. are also moisturizing: they capture and retain water in the epidermis and thus reduce the dryness of the skin by half.

  • Lastly, they fight against the phenomenon of glycation, a biological process that causes the degradation of elastin and collagen, essential proteins of the dermal tissue to preserve firm and elastic skin.

Moreover, P.H.A. are smaller molecules than A.H.A. (glycolic acid, lactic acid, citric acid...) and B.H.A. (salicylic acid); thus, they penetrate less far into the skin layers, and are generally well tolerated by all skin types, even the most sensitive ones which cannot apply A.H.A. and/or B.H.A.

What Are the Dangers and Contraindications of PHAs?

There are no adverse effects. P.H.A.-based skin care products can be applied to all skin types, even the most reactive and sensitive.

Nevertheless, as it is an acid, we advise you to carry out a skin tolerance test before using this active ingredient daily. To do this, apply a few drops of the product to the hollow of the arm and wait 24 hours. If you do not observe any reaction, you can apply the product to the face.

Finally, PHAs have no negative reactions from sun exposure, unlike AHA and BHA.

In Which Skin Care Products Can You Find PHAs?

PHAs are most often found in exfoliating serums, toning lotions, cleansing gels and face masks. Typology has developed three products based on PHA:

  • The exfoliating cleansing gel with 5% P.H.A. and aloe vera is made of 98% naturally derived ingredients. It unclogs pores, evens out the complexion and smoothes the skin texture. It is recommended for dull skin and skin prone to blackheads.

  • The peeling mask is an exfoliating gel that combines the action of AHA and PHA to act at different depths of the epidermis and eliminate dead cells. The complexion is unified and the texture of the skin smoothed. It is used in the evening, once or twice a week.

  • The anti-scarring serum is enriched with lightening and repairing active ingredients, such as gluconolactone from the P.H.A. category and Centella asiatica extract. To fade acne scars, apply a drop locally on the affected areas, at night only.

The scalp scrub is a pre-shampoo exfoliating gel that gently removes dead skin cells for a healthy and balanced scalp. It offers a double chemical and mechanical exfoliation: the P.H.A. dissolves dead skin cells 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 protects against ultraviolet radiation in an in vitro model of cutaneous photoaging. Dermatologic Surgery  (2004).

  • HEARING V. J. & al., Applications of hydroxy acids: classification, mechanisms, and photoactivity. ClinicalCosmetic and Investigational Dermatology (2010).

  • ROTSZTEJN H. & al. Lactic and lactobionic acids as typically moisturizing compounds. International Journal of Dermatology (2019).

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