PHAs (polyhydroxy acids) are chemical exfoliants. They belong to a group of acids whose molecular size is larger than AHAs (alpha hydroxy acids) and BHAs (beta hydroxy acids), meaning that they don’t penetrate the skin as deeply and are better suited to those with sensitive skin or skin concerns. Here is everything you need to know about PHAs.
What are PHAs?
Polyhydroxy acids are second-generation AHAs (alpha hydroxy acids). They exfoliate dead skin cells which build up on the surface of the skin, to brighten the complexion and tighten pores. This chemical desquamation, or peeling effect, also helps ingredients in other skincare products to more deeply penetrate the skin, improving their effectiveness.
The three PHAs most commonly used in cosmetics are:
Gluconolactone or gluconic acid is a PHA that is naturally present in skin cells. It’s an antioxidant, and is very effective against inflammation ;
Galactose is also naturally present in the body. Its role is to stimulate collagen production ;
Lactobionic acid is derived from lactose, and has a hydrating and soothing effect.
The benefits of PHAs in skincare
PHAs are real allies in maintaining healthy skin, with multiple benefits and working in different ways to exfoliate imperfections and brighten dull and tired complexions:
PHAs are known for their keratolytic effect. They help to get rid of dead skin cells that block pores, and smooth your skin’s texture by dissolving intercellular bonds and stimulating skin cell renewal. This is known as chemical exfoliation. They help to prevent the appearance of blackheads and slow the signs of ageing, such as fine lines and wrinkles.
Several studies have shown their anti-inflammatory properties. PHAs are especially effective on oily skin which may be prone to breakouts and/or which has pigmentation marks caused by post-inflammatory hyperpigmentation.
PHAs are also hydrating: they capture and retain water in the skin to reduce skin dryness by half.
Finally, they fight against glycation, a biological process which causes degradation of elastin and collagen, both of which are essential proteins that keep skin firm and plumped.
PHAs are smaller molecules than AHAs (glycolic acid, citric acid and lactic acid) and BHAs (salicylic acid), so they penetrate less deeply into the skin and are generally better tolerated by all skin types, even the most sensitive which can’t use AHAs and/or BHAs.
What are the dangers and contraindications of PHAs?
There are no contraindications of PHAs. Skincare products made with PHAs can be used on all skin types, even the most sensitive or reactive.
However, given that they are still acids, we advise you to do a skin tolerance test before using PHAs everyday. To do this, apply a few drops of the product on the inside of your arm and wait for 24 hours. If you don’t have any reaction, you can use the product on your face.
Finally, PHAs have no contraindications for sun exposure, unlikes AHAs and BHAs.
Which products contain PHAs?
PHAs are most often found in exfoliating serums, toners, cleansing gels and face masks. At Typology, we’ve developed three products with PHAs:
Our exfoliating cleansing gel with 5% PHA and aloe vera is formulated with 98% natural ingredients. It unblocks pores, evens out your skin tone and smooths your complexion. It works best on dull skin, or skin that is prone to blackheads.
Our peeling mask with red fruit acids is an exfoliating gel that unblocks pores and brightens your skin. It has a triple exfoliating effect: chemical, enzymatic and mechanical. It should be used once or twice a week.
Our anti-mark serum is packed with brightening and healing ingredients, like gluconolactone from the PHA category and Centella asiatica extract. To reduce the appearance of acne scarring, apply this serum to affected areas, in the evening only.
Our scalp scrub is a pre-shampoo exfoliating gel that gently gets rid of dead skin cells to leave your scalp healthy and rebalanced. It offers both chemical and mechanical exfoliation: PHA dissolves dead skin cells and stimulates scalp hydration, while jojoba beads gently exfoliate the scalp and stimulate blood microcirculation.
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. Clinical, Cosmetic and Investigational Dermatology (2010).
ROTSZTEJN H. & al. Lactic and lactobionic acids as typically moisturizing compounds. International Journal of Dermatology (2019).