Polyhydroxy acid (PHA) is quickly emerging as a star player in skincare. It is a type of alpha hydroxy acid that has a larger molecule and is less irritating than traditional AHAs. Because of this, PHAs are often described as the gentler cousin of glycolic acid and lactic acid, and they are also more hydrating. Their skin-transforming benefits and lower tendency to irritate or dry the skin have quickly made them a sought-after ingredient. In this post, we explore how PHAs work, who they suit best and how to get the most out of them in your routine.
What is Polyhydroxy Acid (PHA)?
Polyhydroxy acids are chemical exfoliants that lift away dead skin cells from the surface. They belong to the same family as AHAs and beta hydroxy acids, but they have a much larger molecular structure. As a result, they cannot penetrate as deeply or as quickly, so they work mainly on the outermost layer of the skin. This is exactly why they tend to be gentler and far less likely to trigger redness or stinging. The most common PHAs are gluconolactone, lactobionic acid and galactose. Alongside their exfoliating action, they also draw moisture into the skin, which sets them apart from harsher acids.
What’s the Difference Between PHAs and AHAs?
PHAs and AHAs share the same goal of exfoliation, however the way they behave on the skin is quite different. The distinction comes down to molecule size, how deeply each one penetrates and how much hydration it provides.
The biggest difference is molecular size. AHAs such as glycolic acid are small, so they sink quickly into the skin and exfoliate at a deeper level. This makes them effective, but it also makes them more likely to cause irritation, dryness or stinging. PHAs are much larger, much like mandelic acid is larger than other AHAs, so they exfoliate slowly and stay near the surface. Because of this, they suit sensitive skin and anyone who has struggled with stronger acids. PHAs also hold onto moisture far better than most AHAs, so they hydrate whilst they exfoliate rather than leaving the skin tight and dry.
What are the Benefits of PHA for Skin?
PHAs deliver many of the same results as stronger acids, but they do so with far less risk of irritation. Here are the main ways they benefit your skin:
- Gentle exfoliation: PHAs lift away dead skin cells and encourage cell turnover without triggering redness or irritation. This is a sharp contrast to the harsher, drying nature of traditional AHAs. It also makes them an excellent choice for dry or sensitive skin, and for anyone who wants to exfoliate alongside stronger actives like tretinoin.
- Long-lasting hydration: PHAs are humectants, which means they draw in and hold water within the skin. As a result, your complexion stays soft, supple and comfortable. This is especially helpful if you have dry or ageing skin that struggles to retain moisture.
- Antioxidant protection: PHAs help neutralise free radicals from UV light and pollution. These unstable molecules damage skin cells and drive fine lines, wrinkles and other signs of ageing. By mopping them up, PHAs help protect the skin and repair existing damage over time.
- Brighter, more even tone: PHAs gradually fade dark spots and improve uneven tone, so they are a popular choice if you are dealing with hyperpigmentation. With regular use, the skin looks clearer and more radiant.
- Smoother texture: By refining the surface and boosting radiance, PHAs leave the skin smoother to the touch. This is great for those with scarring, ageing or dry skin who want a more polished, glowing complexion.
What Types of PHA are There?
Not all PHAs are the same, and each one has slightly different strengths. The three you are most likely to see on an ingredients list are gluconolactone, lactobionic acid and galactose.
- Gluconolactone: This PHA is derived from sugar. It is a gentle exfoliant that helps soften the look of wrinkles, fine lines, age spots and uneven tone. Gluconolactone is also a humectant, so it attracts water to the skin and keeps it hydrated.
- Lactobionic acid: This PHA is derived from milk and behaves much like gluconolactone. It is a humectant too, so it softens the look of wrinkles, fine lines and age spots whilst staying very gentle on the skin.
- Galactose: This PHA is also derived from sugar and is used less often than the other two. It gently exfoliates and refines the look of fine lines and uneven tone. Galactose also has anti-inflammatory properties, so it can calm redness and help with acne-prone skin.
Which PHA is Best for Your Skin Type?
The best PHA for you depends largely on your skin type and what you want to achieve. Matching the acid to your needs will help you get results without overdoing it.
As a general rule, gluconolactone is a good option if you have dry skin, because it is the strongest humectant of the three. If your skin is sensitive, lactobionic acid tends to be the kindest choice, since it is the most soothing and least likely to irritate. For acne-prone skin, gluconolactone, lactobionic acid and galactose can all help. They clear away dead skin cells and unclog pores, which in turn reduces the breakouts that come from congestion. Whichever one you choose, a well-layered routine will help you get the most from the ingredient.
How Do You Use PHAs in Your Skincare Routine?
PHAs are easy to add to most routines, and they are forgiving enough for beginners. The key is to introduce them slowly and to protect your skin from the sun.
PHAs come in a wide range of formats, including cleansers and toners, serums and moisturisers. Leave-on products such as serums tend to work best, because they give the acid enough time to exfoliate. If you are new to acids, start with a low concentration and use it only a few times a week. You can then build up the frequency as your skin gets used to it. PHAs also pair well with other ingredients, including retinoids, vitamin C and peptides, so they slot neatly into an active routine. Crucially, PHAs can make the skin more sensitive to sunlight. Always finish your morning routine with a broad-spectrum sunscreen of SPF 30 or higher.
Is PHA Safe?
PHAs are generally safe and well tolerated, even by those with reactive skin. That said, no exfoliating acid is completely without risk, so a little care goes a long way.
Most people use PHAs without any trouble, although they can occasionally cause mild dryness, redness or irritation. To stay on the safe side, always patch test a new product first. Introduce it gradually rather than all at once. If you notice persistent irritation or any signs of an allergic reaction, stop using the product and speak to a doctor. With a slow and steady approach, PHAs reward your patience with smoother, brighter and better-hydrated skin.
At City Skin Clinic, we are passionate about personalised skincare. Our online skin clinic offers safe and effective custom skincare treatments. Where appropriate our doctors use ingredients such as tretinoin and hydroquinone to treat skin conditions like acne, hyperpigmentation, melasma and skin ageing. To start your personalised skincare plan, book a virtual video consultation or use our online consultation form. The journey towards great skin starts here.
This article is intended for general informational purposes only and is not a substitute for medical advice, diagnosis or treatment. Always consult a qualified medical provider for any medical concerns or questions you might have.
