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Alpha Hydroxy Acid

Written by: Becki Murray

Last Updated: 4 June 2024

Alpha hydroxy acids, often referred to as AHAs, are group of naturally-occurring acids that are best known for their exfoliating effects. They work by exfoliating the outer layer of the skin, promoting cell turnover, and helping to fade hyperpigmented areas. Used in both at-home skincare products and in skin peels, they are often found in the form of acid toners, although you may also find them in some exfoliating cleansers. AHAs fall into the same broad category as BHAs and PHAs, but they have their own unique characteristics.


What are the benefits of AHAs for the skin?

AHAs work by dissolving the chemical bonds holding dead skin cells onto the surface of the skin. That’s pretty useful because the skin is constantly renewing itself, with fresher layers being produced from within the dermis, and pushing up towards the surface of the skin as the outermost layers of cells die and are shed. However, the dead cells don’t always shed so easily due to the

chemical bonds (you can think of them as a kind of cellar ‘glue’) holding the dead skin cells onto the surface of the skin.

Alpha hydroxy acids can work their way around these bonds and effectively dissolve the glue, which allows the outermost dead skin cells to be wiped or washed off of the face, revealing the fresher, brighter skin underneath. Thus, AHAs can improve the radiance, texture and hydration of your complexion.

How do alpha hydroxy acids improve the skin?

AHAs work to improve the texture and radiance of the skin by exfoliating its surface. This makes your skin smoother, and can improve the hydration of the skin from within. Exfoliation helps keep pores unblocked too, so AHAs can help to keep skin that tends to be spotty or congested, that bit clearer. AHAs also stimulate collagen formation, so they can contribute to firming and strengthening the skin and reducing the appearance of wrinkles. By removing dead, pigmented cells from the surface they can help patchy pigmentation look more even, as well.

Can alpha hydroxy acids reduce dark spots and hyperpigmentation?

Yes – and that’s one of their main selling points. They can help with dark marks due to their exfoliation effect and because they also enhance the penetration of other skin-brightening and anti-inflammatory ingredients, such as vitamin C and niacinamide, by removing dead skin cells.

What types of AHAs are there?

There several different AHAs and they vary in the strength and immediacy of their effects: glycolic acid (from sugar cane) is one of the strongest. That’s because it has a smaller molecular size, so it reaches more deeply into the skin, more swiftly. Lactic acid (from sour milk) and malic acid (from apples) are more gentle as their larger molecules don’t penetrate the skin as deeply as glycolic acid can do. Citric acid (from citrus fruits) and tartaric acid (from grapes) are two other examples of alpha hydroxy acids. Phytic is the gentlest of the AHAs, but it is used more as an antioxidant than as an exfoliant.

How do AHAs compare to BHAs and PHAs in skincare?

Consider AHAs as your main brightening and fine line-reducing solution within the acid toner category, especially if you don’t have overly sensitive skin. AHAs can also help reduce the risk of breakouts, but that’s where BHAs really come into their own, and if you do struggle with sensitivities, PHAs offer a gentler (and increasingly popular) option that can still get you great chemical exfoliation results over time.

Which AHA is most effective for dry skin?

AHAs can be great for dry skin as they can have a hydrating effect while they exfoliate. One of the best in the category is lactic acid, which is fairly large in size so is less potent than some other options, such as glycolic. However, if hydration is your main concern, you are probably better looking at other non-exfoliating acids, such as hyaluronic.

Can acid toners be used for anti-ageing for wrinkles and fine lines?

AHAs can contribute to your anti-ageing results due to their exfoliating abilities and how they improve skin texture. They also stimulate the production of collagen in the skin, helping improve skin firmness and elasticity, as well as enhancing hydration that can lead to a subtle plumping effect.

How do AHA acid toners complement other skincare?

After using your AHA toner you can apply a treatment serum if you are using one, and/or a moisturiser. In the morning, make sure you always finish your skincare regime with a sunscreen. You should be wearing sunscreen every day as a matter of course, but it is particularly important if you are using an acid toner. That’s because alpha hydroxy acids make your skin more sensitive to sunlight and the potential for photo-ageing caused by UV light.

What is the best concentration of AHA for skincare?

The optimal concentration of alpha hydroxy acids can vary based on individual skin sensitivity, tolerance, and the specific goals you have for your skincare routine, but, for at-home use, AHA products typically range from 5% to 15% concentration.

Low concentrations (5-7%) are best for beginners or those with sensitive skin as they provide gentle exfoliation without causing excessive irritation. Medium concentrations (8-10%) offer a balance between potential irritation and effectiveness, helping you increase the exfoliating benefits of your AHA products, while high concentrations (12-15%) provides more intense exfoliation for those wanting maximum effects for their more resilient skin.

Can I use AHAs with retinol?

Not at the same time. Use them on alternate nights. Using them simultaneously would really run the risk of irritating your skin, so you definitely need to be cautious and avoid using them at the same time. I would build up to using the toner a couple of times a week in the morning, and then use the retinol at night. Also, depending on the formulation of the product, retinol may counteract the effects of the glycolic acid.

Added to this, you need to know that if you’re using an alpha hydroxy acid lotion in the evening, you’ll get stronger results if you don’t put anything on afterwards. Any product with water in it – e.g. serum or moisturiser – will neutralise the acid, so it’s stronger if you leave it on its own. If you’re wondering what that means for the acid toner you were planning to use before your serum and sunscreen – it’s fine, but you’ll get more of an exfoliating, brightening result if you used the acid product on its own in the evening.

Can you combine AHA with vitamin C in your skincare routine?

Yes you can – a lot of people will use an acid toner in the morning and then put a vitamin C straight on afterwards. If your skin doesn’t like this combination, however, just don’t do it.

How often should you use Alpha Hydroxy Acids? What are the risks of overusing AHAs?

I’d start off by using your AHA toner twice a week at first, and seeing how your skin responds. If your skin is fine with it, then step your usage up to every other day. Lots of people seem to like to use glycolic toners every day, but I would not advise this – multiple skincare experts have advised me that we tend to overuse alpha hydroxy acids, which can end up damaging the skin barrier and leading to pigmentation issues. You should also avoid using both an acid toner and a face wash with AHAs in your routine simultaneously as this is likely to be too much for your skin to handle.

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

If your AHA product is irritating your skin – i.e. leaving it peeling, red and sore – then step down your usage. Always respond to how your skin is reacting to a product, and don’t think that you should ‘push through’ any redness or irritation. Redness signals inflammation, which is bad for the skin, so if your skin is unhappy, back off and go more slowly.


How to use alpha hydroxy acid (AHA) exfoliants?

This depends on the formulation your alpha hydroxy acid is in. Whichever product you are using, follow the directions on the packaging. Some AHA exfoliants are cleansers, in which case you use them like a regular cleanser and wash them off. Some, however, are leave-on (such as toners or creams) – these you use after cleansing. If it’s in a cream, use this like any other face cream – although I’d be careful around your eyes.

How to use your AHA toner?

AHA toners are increasingly the most common way to use the exfoliating ingredient. Simply, wet a cotton pad with some of the toner, and wipe it over a clean, dry face (i.e. use this toner after cleansing, so that the toner doesn’t have to fight its way through grime and oil on the surface of your skin in order to do its job).

What are the best AHA toners?

You can find our favourite AHA toners in The Tweakment Guide skincare shop or receive personalised recommendations for your skin type and concerns by booking in with our skincare consultant Shanaz for a one-to-one appointment.

FAQ ABOUT Alpha Hydroxy Acid

What acid toners are best for daily use?

As mentioned, we probably wouldn’t recommend use your AHA toner every day as it can lead to skin barrier issues, causing dryness and irritation. If you really want to, still make sure to build up to daily use gradually, and keep to a milder AHA formula. A PHA-based product may also be better suited to daily use.

Is it safe to use AHA under the eyes?

You can use AHAs to brighten the under eye area, but the skin around the eyes is thinner and more delicate compared to the rest of the face, making it more sensitive. That’s why it is important to exercise caution when using them near the eye area. If you really want to use them, consider gentler formulations and patch test your chosen product before applying to the eye area to avoid any irritation. Wearing SPF up to the eye area is also really important.

What skin types are best suited for AHA treatments?

AHAs can be used on all skin types, although they are especially good for anyone with the following concerns: dull skin, dark spots, and fine lines or wrinkles. If you are prone to sensitive skin however, it is best start with a low-strength AHA – aka lactic or mandelic over glycolic – to ensure your skin doesn’t react.

What are the best toners for skin texture improvements?

AHAs can be a great option for improving uneven skin texture. Glycolic acid is known for its exfoliating properties, helping remove dead skin cells and promote smoother skin texture. A gentler option is lactic acid. It moisturises as it exfoliates your skin, making it suitable for those with sensitive skin.

Is alpha hydroxy acid the same as glycolic acid, and what are the benefits?

Glycolic acid is a type of alpha hydroxy acid. So glycolic acid is an AHA, but there are more types of AHA than just glycolic acid. While the alpha hydroxy acids are generally quite similar in terms of the benefits they confer on your skin, glycolic acid in particular has the added benefit of boosting collagen levels in the skin – which is very helpful for ageing and wrinkling skin, as collagen is the protein that keeps skin firm. A glycolic acid toner can help calm down acne by unblocking the pores on the surface of the skin, but it can’t reach into blocked pores in the way that a salicylic acid toner can.

What is a mandalic acid toner good for?

If you find glycolic acid a little too potent for your skin, mandalic acid can be great gentler alternative that still delivers all the benefits of AHAs. Especially recommended for Black skin because it doesn’t run the risk of causing post-inflammatory pigmentation, it can brighten, smooth and clear your complexion.

Do alpha hydroxy acids accelerate ageing?

It’s definitely a misconception that AHAs can accelerate ageing – in fact they do the reverse and help prevent it!

You may have heard people say that alpha hydroxy acids ‘thin the skin’. That doesn’t sound like a good thing, does it? Thin skin can wrinkle more easily, so if AHAs actually did thin the skin, then you would be absolutely right that this would be a problem. The thing is, they don’t. While they thin the upper surface very slightly (because they’re getting rid of the outermost cells, which are dead anyway), they actually thicken the dermis (the lower layers of the skin). They manage to do this by supporting and hydrating these lower layers of the skin, and stimulating collagen production in them. So no, alpha hydroxy acids don’t thin the skin. Using AHAs will, over time, make skin thicker and firmer.

How do Alpha Hydroxy Acids prevent ageing?

Another reason why there’s a misconception about AHAs and ageing is that in the early 2000s, a study by the European Commission’s Scientific Committee on Cosmetic Products revealed that a number of studies had shown that alpha hydroxy acids appeared to lead to an increase in damaged skin cells, and cause reddening, blistering and burning of the skin as well as making it more vulnerable to UV damage. However, according to leading dermatologists, this was down to consumers not using the products properly – using them too frequently, using them improperly, and using them even when their skin was too sensitive to deal with the products. There’s no longer this sort of concern around AHA use, but I’d still advise you to be sensitive to how your skin responds to whichever products you’re using, and to keep this in mind when choosing how frequently to use your desired products. Even if you love the glow they give your skin, don’t overuse them.

Are AHA toners like a chemical peel at-home?

The type of acid toners you can buy for at-home use are not as strong as those used by a practitioner in clinic – and for good reason! No one wants chemical burns on their face. However, AHAs can provide a brightening effect and address mild dark spots and discolouration over time, so they are a good first step for anyone not yet ready for a full-strength peel.

Does alpha hydroxy acid expire?

Yes – check the label for the expiry date of your products. All beauty products, by law, have a symbol on the packaging to show how long they will last for once they’ve been opened. Your product may well be safe to use longer than this suggests, but it may not be fully effective.



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Alice answers your question. Want to ask Alice a question? Pop it in here and check back in a few days for the answer.

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