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Dr. Shreya Andric is a dermatologist based in Sydney. She is passionate about skin health and her mission is to educate the public on how to care for their skin, and also clear up the vast amount of misinformation out there on this topic.
While Dr. Andric has independently chosen the products that appear in this article, she does not receive revenue from the links. Some of the links may return revenue to Yahoo Lifestyle Australia.
Polyhydroxy acids (PHAs) have been gaining momentum in the skincare arena of late, but what exactly they are, how do they work, and how do they compare to their cousin, alpha-hydroxy acid (AHA)?
PHAs are chemical exfoliants that are chemically related to AHAs – PHA molecules have longer acid chains than AHAs and because of their size, have a slower rate of absorption into the skin. The most well-known PHAs are gluconolactone, galactose, and lactobionic acid, which is derived from lactose in cow's milk.
What do PHAs do?
PHAs work in a very similar way to AHAs – they exfoliate dead skin cells on the surface of the skin, resulting in a more even skin tone and texture. This also helps skincare ingredients to penetrate deeper into the layers of your skin, which therefore makes them more effective. PHAs are also rich in antioxidants and stimulate epidermal growth and repair.
The additional benefits of PHA come from their greater humectant (moisture-retaining) and moisturising properties. PHA-treated skin shows less water loss and less skin irritation than glycolic and lactic acid-treated skin. PHAs are used in many cosmetic formulations because they produce similar results to AHA and are tolerated by more sensitive skin types.
Compared to AHAs, preliminary studies of PHA have been shown to have equivalent anti-ageing effects. One study compared 8% glycolic acid day cream and 8% glycolic acid night cream with a PHA regimen of 4% gluconolactone day cream and 10% gluconolactone night cream – similar benefits were obtained with both regimens when looking at fine lines, wrinkles, pore size, skin roughness, firmness, mottled pigmentation and clarity.
Both regimens were well-tolerated, however, patients had increased burning and stinging with the AHA product compared to the PHAs. Other studies of PHA in women with sensitive skin and sun damage have shown improvements in fine lines and wrinkling around the eyes (crows feet). People with dark skin types obtain similar benefits without significant irritation.
AHAs and PHAs are commonly used in treatment of acne and rosacea. PHAs in general are better tolerated by patients with rosacea because they have less burning and stinging. They are also preferred in patients with eczema as they will help to smooth and retexturize the skin without irritating it.
Whilst AHAs make the skin more sun-sensitive, PHAs do not seem to have this property, which makes them safe to use morning or night.
Which hydroxy-acid should I choose?
I always say that skincare is not one size fits all. The better you understand your skin and its concerns, the easier it is to determine what ingredients are best suited for you. AHAs are generally preferred for normal to dry skin as they penetrate deeper to exfoliate dead skin cells.
Beta-hydroxy acids (BHAs) are better suited to oilier, acne-prone skin as they can enter blocked pores to dissolve sebum and dead skin cells and help to exfoliate acne and prevent post-inflammatory hyperpigmentation. PHAs are a fantastic alternative to both AHAs and BHAs if you tend to have sensitive skin that does not tolerate many chemical exfoliants.
Additionally, if you have dry skin, they are a good option as their humectant properties mean that they attract water and are moisturising.
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