How extensive is your skincare lexicon? Do you know your HA from your AzA? What about your EGF or your NMF? There are acronyms aplenty when it comes to ingredients, because let’s be honest, polydeoxyribonucleotide is far more of a mouthful to say and more challenging to market than PDRN. But hyaluronic acid, azelaic acid, epidermal growth factor or natural moisturising factors aside, it’s when it comes to liquid exfoliants that there is often confusion. For you see, they are categorised in groups, depending on their chemical structure and solubility, adding a layer of decoding beyond simply working out what it means by AHA, BHA or PHA.
“AHAs (alpha hydroxy acids) and BHAs (beta hydroxy acids) are chemical exfoliants that dissolve the bonds holding dead skin cells together, allowing them to shed more evenly,” explains aesthetics doctor Dr Ahmed El Muntasar. “The main difference is that AHAs are water-soluble and work primarily on the skin’s surface, making them excellent for improving texture, brightness and pigmentation. BHAs are oil-soluble, meaning they can travel into the pore itself to dissolve excess oil and debris, making them particularly effective for oily and acne-prone skin.”
As it is not simply a question of whether an AHA or BHA is better suited, but which acids within those classifications are designed for each skin type or concern, Vogue has consulted four experts to find out everything we need to know about liquid exfoliants, how to introduce them into our routines, the ingredients to layer alongside them and how to use them safely. Scroll on to learn more and delve in to the AHA vs BHA debate.
What are AHAs and BHAs, how do they work and how do they differ?
Unlike physical scrubs that, as the name suggests, use gritty, textured agents like sugar, coffee grains, jojoba beads or salt to buff away dead skin cells, AHAs and BHAs fall into the camp of liquid exfoliants that gently dissolve pore-clogging elements with chemicals to leave skin smooth, soft and brighter. But these classes of hydroxy acids work in slightly different ways. As referenced by Dr El Muntasar above, but as put by plastic surgeon Dr Dirk Kremer, “AHAs are water-soluble and work primarily on the skin’s surface, making them particularly useful for improving texture, dullness, fine lines and uneven pigmentation. BHAs are oil-soluble, which allows them to penetrate oil-filled pores. This makes them particularly useful for oily or acne-prone skin, blackheads and congestion.” Skincare expert Laura Porter puts it simply: “AHAs are brilliant surface workers; BHAs are particularly useful when congestion and oil are part of the problem.”
medicube Zero Pore Pad
What are the most common types of AHAs and BHAs used in skincare?
While many different AHAs are commonly used in skincare (and we will get onto them), generally speaking, BHAs refer mostly to one particular blemish-busting ingredient: salicylic acid. “When we talk about BHAs in skincare, we’re usually talking about salicylic acid,” confirms cosmetic surgeon and aesthetics specialist Dr Paul Banwell. “It’s particularly good for oily or congested skin because it can work inside the pore rather than just exfoliating the surface.”
Paula’s Choice Skin Perfecting 2% BHA Liquid Exfoliant
When it comes to AHAs, the ones that come up time and time again are glycolic acid, lactic acid and mandelic acid. Dr Dirk Kremer explains why these are the most ubiquitous: “Glycolic acid has the smallest molecular size of the commonly used AHAs and therefore, penetrates the epidermis more readily, making it particularly effective for improving texture, dullness, pigmentation and fine lines,” while lactic acid “has a larger molecular size, tends to be gentler and also has hydrating properties.” Mandelic acid is favoured for its gentle nature. Dr Banwell says, “Mandelic acid is another AHA and tends to work more slowly, so some people with more sensitive skin find it easier to tolerate.”
Which skin concerns are best treated with AHAs and which respond better to BHAs?
“A simple way of looking at it is that AHAs tend to be better for concerns on the surface of the skin, while BHAs are particularly good when congestion and oil are involved,” says Dr Banwell. So with this surface vs. pore theory in mind, AHAs, adds Dr El Muntasar, “are ideal for concerns including dullness, uneven skin tone, sun damage, pigmentation, rough texture and early signs of ageing. They also stimulate collagen production over time, helping to soften fine lines.” BHAs, on the other hand, he reveals, “are the treatment of choice for excess oil, enlarged pores, blackheads, whiteheads and inflammatory acne because they exfoliate inside the pore as well as on the skin’s surface. They also have anti-inflammatory properties, making them particularly useful for acne-prone skin.”
How can someone determine whether they should use AHA vs BHA?
Dr El Muntasar shares this handy guide based on the most common skincare concerns:
- Dry or dehydrated skin: Lactic acid is often the best starting point because it exfoliates while supporting hydration.
- Oily or acne-prone skin: Salicylic acid is generally the most effective option because it removes excess oil from inside pores.
- Combination skin: Some people benefit from alternating an AHA and a BHA on different evenings depending on which areas need attention.
- Acne and blackheads: Salicylic acid remains the gold standard.
- Minimising the appearance of pores: Salicylic acid is more effective because it clears congestion that makes pores appear larger.
- Uneven skin tone and hyperpigmentation: Glycolic acid or lactic acid can help accelerate cell turnover and gradually improve pigmentation.
- Fine lines and wrinkles: Glycolic acid has the strongest evidence for improving collagen stimulation and skin texture.
- Rough or textured skin: AHAs generally perform better by smoothing the skin’s surface.
- Sensitive skin: Gentler options such as mandelic acid or lower-strength lactic acid are usually better tolerated.
How can beginners introduce exfoliating acids without irritating their skin?
The experts all agree that the best way to introduce exfoliants into your routine is with a slow and steady approach. “The biggest mistake I see is people starting with high strengths every day because they want faster results. Skin rarely rewards that approach,” stresses Dr El Muntasar. Dr Kremer concurs, “More is definitely not better when it comes to exfoliation. Over-exfoliation can disrupt the skin barrier and actually make the skin look and feel considerably worse.”
He says the best approach is this: “I would recommend introducing one exfoliating acid at a time, initially once or twice a week, rather than immediately using it every day. Start with a relatively low concentration and increase the frequency gradually only if the skin tolerates it well. Burning, persistent redness, excessive dryness, flaking or increased sensitivity are signs that the skin barrier may be becoming irritated and that the product should be reduced or stopped. I would also avoid introducing several strong active ingredients at the same time. Keep the rest of the routine simple, use a good moisturiser to support the skin barrier and always use broad-spectrum SPF during the day, as exfoliating acids can make the skin more sensitive to sunlight.”
How often should AHAs and BHAs be used?
There is no universal frequency or schedule. Instead, according to Dr Kremer, “It depends on the type and concentration of the acid, the formulation and most importantly, how well the individual skin tolerates it.” Every person is different. “Some people will eventually be able to use them more regularly, while others will get everything they need from using an acid a couple of times a week,” adds Dr Banwell. “There isn’t a prize for exfoliating every day. If your skin is becoming dry, tight, red or sensitive, that’s a fairly good indication you’re doing too much.”
Treat your skin like a plant, says Porter. “Nourish it, protect it and give it what it needs – don’t keep interfering with it because you want it to grow faster.”
Is it safe to use both in the same skincare routine?
While you technically can include both AHAs and BHAs in your routine, it is important to consider whether this is actually what is needed and, if so, how to do it cautiously. Dr Kremer agrees, “Because both exfoliate the skin, using too much of either, particularly at higher concentrations, can lead to irritation, dryness and disruption of the skin barrier.” He adds that you can be tactical with their usage. “A gentler approach is to alternate them on different days, choosing the acid according to what the skin needs. There are also professionally formulated products that combine AHAs and BHAs at concentrations designed to work together safely.”
Dr Dennis Gross Alpha Beta® Universal Daily Peel
Can AHAs or BHAs be combined with retinol, vitamin C, niacinamide or peptides?
While each of these ingredients has a role and is designed to tackle different skincare concerns, layering active ingredients like retinol and vitamin C needs to be done carefully. Dr Kremer advises, “Vitamin C can also be used in a routine containing exfoliating acids, but particularly with stronger or more acidic formulations, using several active ingredients together may increase irritation. A simple option is to use vitamin C in the morning and the exfoliating acid in the evening.”
As for retinol, it is known to be irritating to the skin. “Both retinoids and exfoliating acids can cause dryness, peeling and irritation, so layering them in the same application is often unnecessary, particularly for beginners or sensitive skin,” he continues. “Alternating them on different evenings is generally a more sensible approach.”
Niacinamide is well-tolerated, can assist in supporting the skin barrier and may calm irritation caused by the exfoliating ingredients. Similarly, peptides work well with AHAs and BHAs, encouraging skin repair. “Peptides are generally very compatible with AHAs and BHAs,” says Dr Kremer. “Unlike retinol, they are not inherently irritating and can usually be used in the same routine without difficulty. In fact, peptides may help support skin repair and hydration, making them a useful complement to exfoliating acids, particularly in patients looking to maintain a healthy skin barrier.”
Dr Banwell wants to make clear, “One of my bugbears with skincare at the moment is the idea that you need to layer endless active ingredients to have a ‘good’ routine. You really don’t. A few well-chosen products that suit your skin will usually serve you much better.”
Why is sunscreen especially important when using exfoliating acids?
SPF is a daily non-negotiable no matter the season, but it is vitally important when using exfoliating acids for two reasons. First and foremost, acids can make the skin more sensitive to sunlight. Dr Kremer confirms, “AHAs remove some of the superficial dead cells from the outermost layer of the skin, which can make the skin more sensitive to ultraviolet radiation and therefore more susceptible to sunburn and sun damage.” But secondly, UV damage is the biggest cause of skin ageing. “If you’re spending money on products to improve pigmentation, fine lines and skin tone but not protecting your skin from the sun, you’re fighting a losing battle,” details Dr Banwell. Put plainly, it is counterproductive to use exfoliants to improve pigmentation, fine lines and more and then not shield your skin from external aggressors that cause the aforementioned to occur. Dr El Muntasar advises broad-spectrum SPF 30 “as a minimum, although SPF 50 is preferable for anyone actively treating pigmentation or signs of photoageing.”
What are the signs of over-exfoliation?
“Your skin normally tells you”, stresses Porter. Much like you would expect, when your skin feels irritated, burning, stinging or you notice redness, peeling or tightness, these can all be signs of excessive sloughing and a disruption to the skin barrier. You may also see, according to Dr Banwell, that “products you’ve used happily for years now sting when you put them on are all warning signs, or you can also see more breakouts or lots of little bumps.” When the latter occurs, he wants to point out that this is not necessarily a positive skin shedding. “People sometimes assume this is the skin ‘purging’ and respond by exfoliating even more, which can make the situation considerably worse.”
What concentration should beginners look for?
While concentration is not the only thing to look out for, all the doctors agree that a lower concentration is best when beginning on your exfoliation journey. “Lower concentrations are both safer and more effective in the long term,” says Dr El Muntasar who also shares a general guide, detailing glycolic acid should be around 5 per cent, lactic acid at 5 to 10 per cent, mandelic acid at around 5 to 10 per cent and salicylic acid from 0.5 to 2 per cent. This is not an indication of how irritating or potent a product may be, however. “The formulation, pH, frequency of application and the individual’s skin type all matter,” stresses Dr Kremer, adding: “The aim is controlled, gradual exfoliation rather than producing an immediate reaction. Tingling is not a measure of effectiveness, and stronger does not necessarily mean better.”
