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Polyhydroxy Acids

Written by: Becki Murray

Last Updated: 9 February 2024

In skincare, PHAs refer to Polyhydroxy Acids. These are a type of chemical exfoliant that belong to the same family as AHAs (Alpha Hydroxy Acids) and BHAs (Beta Hydroxy Acids). What sets PHAs apart though (and makes them an increasingly interesting skincare ingredient for your routine) is that they are particularly gentle acids. That means they can help to exfoliate the skin’s surface, promoting cell turnover and improving the overall texture and appearance of the skin, with less irritation. They are most commonly found in acid toners, but are also cropping up in serums and moisturisers too.

acid toner

How do PHA acid toners work on the skin?

PHA (Polyhydroxy Acid) toners work on the skin by gently chemically exfoliating the surface layer of the skin, promoting cell turnover, and removing dead skin cells. For that reason, they are often grouped together with other exfoliating acids – AHAs (Alpha Hydroxy Acids) and BHAs (Beta Hydroxy Acids) – which work in a similar way.

How do PHAs differ from AHAs and BHAs?

PHAs do differ to other exfoliating acids in one key aspect. Unlike AHAs and BHAs, PHAs have larger molecular structures, which means they penetrate the skin more slowly. This slower penetration results in gentler exfoliation. This makes them suitable for individuals with sensitive skin or those who may experience irritation from other types of chemical exfoliants.

What concerns can PHAs be used to treat?

PHAs can be beneficial for addressing concerns such as fine lines and wrinkles, uneven skin tone, and dullness, while also providing gentle exfoliation without causing irritation.

Aside from exfoliation, what are the benefits of PHAs?

As well as being gentle exfoliators, PHAs have humectant properties, which means they attract moisture to the skin. This helps to hydrate and plump, leaving your complexion softer and smoother. They can also help to strengthen the skin’s moisture barrier. As a result, unlike some other exfoliating acids that can cause dryness or irritation, PHAs can actually help to improve skin hydration, making them ideal for individuals with sensitive or dry skin.

Some PHAs, such as lactobionic acid, have antioxidant properties that help to protect the skin from free radical damage and environmental stressors. This can benefit sensitive skin by reducing inflammation and promoting overall skin health.

Are PHA acid toners suitable for sensitive skin?

Compared to AHAs and BHAs, PHAs are considered particularly beneficial for sensitive skin. As larger molecules, they result in more gentle, surface level exfoliation of dead skin cells. This makes them less likely to cause irritation or sensitivity compared to other chemical exfoliants, so they can be a great option for individuals who may experience redness, stinging or burning with other types of acids.

Do PHAs make your skin more sun sensitive like AHAs?

Unlike alpha hydroxy acids, PHAs aren’t deem to make your skin more sensitive to sun, which is another benefit to their use. However, that isn’t to say that you shouldn’t still be protecting your skin from UV rays. A broad spectrum sunscreen is an integral part of any skincare routine.


How quickly can you see results with polyhydroxy acids?

While you can see similar results from PHAs as you can with AHAs, you will see them more slowly, especially if you have sensitive skin as you should use them at a concentration that your skin will find easier to tolerate.

How often should you use a PHA acid toner?

PHA toners are generally suitable for daily use (unlike other exfoliating acids), but how often you use a PHA toner really depends on your individual skin tolerance, especially for those with sensitive skin. Begin with less frequent use, such as 2-3 times per week, and gradually increase frequency as tolerated.

How long can you use PHAs for?

PHAs are generally well-tolerated for long-term use, allowing individuals with sensitive skin to incorporate them into their skincare routine without concerns of over-exfoliation or skin barrier damage.

How do PHAs complement other skincare products?

Due to their exfoliating nature, PHAs can help other products penetrate the skin more effectively because they remove dead skin cells. They can also enhance the hydration offered by your hydrating products.

Apart from toners, where else can you find PHAs in your skincare?

You can find PHAs in various skincare products besides toners, including:

Cleansers: PHAs are sometimes incorporated into cleansers to provide gentle exfoliation during the cleansing process.

Serums: PHA serums are available to target specific skin concerns such as dullness, uneven texture, and hyperpigmentation.

Moisturisers: Some moisturisers contain PHAs to provide hydration while promoting gentle exfoliation.

Masks: PHA masks offer a more intensive treatment to exfoliate and rejuvenate the skin.

The main thing to bear in mind is that you don’t really want to double up on your use of PHAs (just like with other exfoliating acids). So, stick to using them in just one step of your routine.

FAQ ABOUT Polyhydroxy Acids

What precautions should you take when starting to use PHA acid toners?

As with all new skincare products, you should always perform a patch test on a small area of skin to check for any adverse reactions before applying the product to your entire face. If you have sensitive skin, it can also be useful to start slowly and gradually increase how frequently you use your PHA product to be cautious.

Is a PHA toner right for me?

Yes – they certainly can be, especially if you have sensitive skin. However, if you love your current AHA or BHA toner, it wouldn’t be suitable to introduce a PHA as well. It is a choose one sort of situation.

What are the most common types of PHAs?

Common types of PHAs include gluconolactone, lactobionic acid, and galactose – so keep an eye out for references to these on an ingredients list.


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