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AHA vs BHA: What’s the Difference and How to Choose the Best Acid Exfoliant for Your Skin

  • fitbounties
  • Apr 25, 2023
  • 11 min read

Exfoliation has long been the secret to glowing, healthy-looking skin. But you don’t need a harsh, gritty scrub to get the job done. Alpha- and beta-hydroxy acids are the best way to remove dead skin cells, using chemical (not physical) methods.

Also known as AHAs and BHAs, they’re the two most common families of exfoliating acids you’ll see in skincare products—and they’re often found together.

So how do they actually work? Which type is best for your skin? And can you get better results if you use both of them?

If you’ve been asking these questions, this tutorial is for you. You will learn the difference between AHAs and BHAs, how to choose the right one, and whether it’s beneficial to incorporate both types into one routine. I’m also sharing some of my favourite AHA and BHA products that I always recommend.

What Is AHA?

AHA stands for alpha-hydroxy acid—a type of naturally occurring acid that is present in many foods and milk sugars.1 AHAs work by peeling away dead skin cells, revealing the fresh new skin cells underneath. They do so by weakening the bonds between the cells (corneocytes) in the uppermost layer of our skin, causing them to detach and flake off.1 But how do they do that? Several studies suggest AHAs disrupt these bonds by overloading the cells with calcium. Because AHAs create acidic conditions within the cells and cell adhesions, they allow calcium ions to flow in. The calcium overload not only disrupts the bonds between cells, it also triggers cell death (apoptosis).2,3

Types of AHAs

These are the different AHAs that you will see in skincare products:

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  • Glycolic acid: The most common AHA, derived from sugarcane. It is also the strongest, because of its small molecule size, but that makes it the most irritating, too.4

  • Lactic acid: The second most common AHA, derived from milk. It’s a gentler alternative to glycolic acid, and can be appropriate for sensitive skin.4

  • Mandelic acid: A mild AHA derived from bitter almonds. As it is weaker than lactic acid, it’s usually combined with other acids. However, some experts, such as Dr. Loren Pickart, believe it can be neurotoxic.5

  • Malic acid: A mild AHA derived from apples. Like mandelic acid, it won’t do enough on its own, so you’ll typically see it in combination with stronger AHAs.

  • Tartaric acid: A weak AHA derived from grapes. Instead of acting as an exfoliant, it is more often used to stabilize other acids’ pH levels.

  • Citric acid: A weak AHA derived from citrus fruits. It is similar to tartaric acid because it also regulates pH. It's also used as a preservative.

  • Phytic acid: A weak AHA derived from rice, seeds, and grains. It is commonly used as an antioxidant.

What Is BHA?

BHA stands for beta-hydroxy acid, a type of acid that is derived from willow tree bark, wintergreen leaves or sweet birch bark.6 Just like AHAs, BHAs exfoliate your skin surface by decreasing the adhesion of dead skin cells (corneocytes), causing them to loosen and detach.6 However, this happens by dissolving intercellular lipids, rather than initiating cell death.6,7 Since BHAs are oil-soluble,6 they penetrate below the skin surface as well, exfoliating inside the pores. This allows oil to flow out more freely, preventing the build-up of dead skin and sebum that leads to clogged and stretched-out pores. BHAs also reduce the amount of oil your skin produces,8 and are an effective treatment for inflammatory acne and open comedones.9

Types of BHAs

The main BHA exfoliants you’ll see in skincare products are:

  • Salicylic acid: The most common BHA, and also the strongest. However, it is not as irritating as glycolic acid (the strongest AHA) because of its large molecule size and anti-inflammatory nature.

  • Betaine salicylate: A BHA composed of salicylic acid and betaine (a hydrating amino acid derived from sugar beets). It’s a gentler alternative to salicylic acid, and according to data from the manufacturer, is equally effective.10 (A 4% concentration of betaine salicylate is said to be equivalent to 2% salicylic acid.)

  • Salix alba or willow bark extract: A natural BHA derived from willow bark. The salicin content converts into salicylic acid, but it is much weaker (so it won’t give you as dramatic results).

How AHA and BHA Are Similar

You may have heard that AHAs are best for exfoliating, brightening and anti-aging, while BHAs are only suitable for people with acne. Fortunately, that isn’t true. These are all the benefits that both AHAs and BHAs have in common:

  • Exfoliating and smoothing: AHAs and BHAs are both effective at removing surface dead skin cells and creating a soft, smooth texture.

  • Brightening: Both AHAs and BHAs reduce the thickness of the stratum corneum, the top layer of skin that consists of dead skin cells.11,12 This allows your skin to reflect more light and look more radiant.

  • Fading pigmentation: Since they both encourage the shedding of old, discoloured dead skin cells, AHAs and BHAs work to fade dark spots and even out skin tone.

  • Firming and reducing wrinkles: At higher concentrations, AHAs and BHAs have been shown to increase the density of collagen in the dermis.13,14 That means they can both help to reduce fine lines and wrinkles and improve skin firmness over time.

  • Hydrating: AHAs and BHAs are both humectants—ingredients that help your skin to attract and hold more moisture.

  • Clearing and preventing acne: AHAs and BHAs both help with acne by exfoliating the surface dead skin that can lead to clogged pores.


How AHA and BHA Are Different

There are, however, some important differences between AHAs and BHAs:

  • BHAs penetrate more deeply: Both AHAs and BHAs exfoliate the skin’s surface. But BHAs are oil-soluble, so they can pass through sebum and exfoliate deep within the pores as well.6

  • BHAs reduce oil production: While AHAs have little influence on sebum, BHAs actually slow down its secretion to help control oily skin.8

  • BHAs are more effective for acne: Although both acids can help with mild acne by sloughing off dead skin cells, BHAs also work their magic underneath the skin surface. By deep-cleaning the pores, BHAs not only clear existing breakouts but also help to prevent them long-term. I consider BHAs to be the most effective topical treatment for acne.

  • BHAs “shrink” pores: Technically, you can’t change the size of your pores—but they can look bigger when they are filled with debris. While AHAs don’t affect pores, BHAs can help them look smaller by keeping them clean.9

  • BHAs are less irritating: Any acid can be drying and irritating if you use it at the wrong concentration or pH, or if you apply it too frequently for your skin. However, AHAs (especially glycolic acid) are more often associated with irritation, redness, and inflammation. BHAs are gentler because of their larger molecule sizes, anti-inflammatory benefits and lower required concentrations. According to the late Dr. Albert Kligman (who conducted many studies on hydroxy acids), AHAs need to be used in concentrations of at least 8% in order to be effective, whereas BHAs only need a concentration of 1.5-2%.15

  • AHAs cause photosensitivity: It’s well-known that AHAs increase your skin’s sensitivity to the sun, making it more vulnerable to sun damage and premature aging. While sunscreen is essential always, BHAs actually have some photoprotective effects.16

  • AHAs cause skin wounding: As I mentioned above, AHAs are skin-wounding agents because they encourage cells to self-destruct through apoptosis (programmed cell death). BHAs are non-wounding agents, as they simply dissolve the “glue” between skin cells—which is a more physiological process. Is apoptosis or cell death something to worry about? Maybe, if you’re using strong AHAs regularly. Apoptosis is also induced by toxins such as estrogen, unsaturated fatty acids and radiation, and is “a cellular endpoint of the stress response.”17


Should You Use AHA, BHA or Both?

Now that you’re familiar with the similarities and differences between AHAs and BHAs, what does that mean for your skincare routine? Here are my thoughts: If You Have Acne BHAs are the way to go. Salicylic acid is proven to reduce the number and severity of acne lesions, and is superior to benzoyl peroxide.18 Look for a concentration of 2% salicylic acid or its equivalent, 4% betaine salicylate. Keep in mind that you may experience initial purging, which is normal and beneficial. See my skin purging vs breakout tutorial for more information. If You Have Oily Skin Only BHAs will reduce your oil production. It may take some experimentation to find the best dose for your skin. I suggest between 1-2% salicylic acid, or 2-4% betaine salicylate. If You Have Dry or Sensitive Skin Lactic acid is the best AHA for these concerns, as it’s one of the gentlest and most hydrating acids. Look for a concentration between 5-8% percent to start, moving up as high as 10% if tolerated. However, a mild BHA would be an equally appropriate option, such as 0.5-1% salicylic acid or 1-2% betaine salicylate. If You Have Pigmentation Both AHAs and BHAs will help, but I think BHAs are your best bet—especially if you have darker skin. Unlike AHAs, they won’t trigger post-inflammatory hyperpigmentation, which is a risk for many ethnicities.19 Since BHAs also give you some photoprotection, you’ll be at less risk of creating new pigment, too. Go for a higher concentration if you can, such as 2% salicylic acid or 4% betaine salicylate. To target discolourations even further, use it in conjunction with niacinamide (see this tutorial for layering tips!). If You Have Wrinkles Both AHAs and BHAs have a thickening effect on the dermis, the middle layer of skin with collagen and elastin fibers.13,14 For best results, you’ll want around 8% (or more) glycolic or lactic acid, or 1-2% percent salicylic acid. Again, just keep in mind that AHAs (particularly glycolic acid) can make your skin more inflamed and vulnerable to sun damage, which can exacerbate signs of aging. If You Have “Normal” Skin If you’re blessed with well-behaved skin and don’t have any major concerns, all you need from your acid is mild exfoliation and brightening. I suggest trying a gentle lactic acid (around 8%), salicylic acid (around 1%) or betaine salicylate (around 2%). If You Want to Use AHA and BHA Together If your skin tolerates it, you can layer AHAs and BHAs together in one routine—or use a product that contains both—but there’s no real reason to do so. According to Dr. Kligman: “Salicylic acid does everything AHAs do and more, and does it more effectively.”15 So if you have a good BHA, you don’t need an AHA as well. ⚠️ No matter which acid you choose, it’s important to start at a low concentration and slowly introduce it into your routine. As you build a tolerance, you can increase the frequency of applications to as often as daily (depending on your skin and the product), and even move up to a higher strength if applicable.

The Best AHA and BHA Products

Best Gentle AHA: The Ordinary Lactic Acid 5% + HA

The Ordinary

The Ordinary Lactic Acid 5% + HA is one of the mildest AHAs on the market, ideal for sensitive skin or anyone new to acids. It has 5% lactic acid along with hyaluronic acid, glycerin and propanediol for extra moisture. There’s also a 10% version when you’re ready for something stronger. See my brand review for more details.

Best Gentle BHA: Benton Aloe BHA Skin Toner

Benton

Benton Aloe BHA Skin Toner is a moisturizing and exfoliating toner made with 0.5% salicylic acid in a non-sticky base of 80% aloe vera. That, along with its just slightly acidic pH level, makes it gentle enough for virtually all skin types.

Best K-Beauty AHA: COSRX AHA 7 Whitehead Power Liquid

COSRX

COSRX AHA 7 Whitehead Power Liquid is a K-beauty AHA treatment containing 7% glycolic acid as its active ingredient. It also features 2% niacinamide for extra brightening, and provitamin B5 and hyaluronic acid to moisturize your skin.

Best K-Beauty BHA: COSRX BHA Blackhead Power Liquid

COSRX

COSRX BHA Blackhead Power Liquid is perhaps the best-known K-beauty exfoliant, and for good reason. It’s a 4% betaine salicylate solution spiked with 2% niacinamide, and it gently clears and prevents breakouts while brightening and fading pigmentation. See my in-depth review here.

Best Clean Beauty AHA: Youth To The People Kombucha + 10% AHA Power Exfoliant

Youth To The People

Youth To The People Kombucha + 10% AHA Exfoliation Power Toner is an overnight liquid exfoliant that combines 7% lactic acid with 3% glycolic acid for a total 10% concentration of AHAs. It’s also got kombucha, a prebiotic, to support your skin’s microbiome, and is fragrance- and alcohol-free.

Best Clean Beauty BHA: Farmacy Deep Sweep 2% BHA Pore Cleaning Toner

Farmacy

Farmacy Deep Sweep 2% BHA Pore Cleaning Toner is a cleanly formulated salicylic acid toner that should be well-tolerated by most skin types. Although it has 2% of the active ingredient, it’s free of drying alcohol and irritating fragrance and essential oils.

Best Clean Beauty AHA-BHA: INNBeauty Project Down to Tone Resurfacing Acid Toner

INNBeauty Project

INNBeauty Project Down to Tone Resurfacing Acid Toner gives you a mix of lactic, phytic, malic, salicylic and citric acids in a potent but non-irritating serum. It’s also packed with gluconolactone, glycerin, propanediol and niacinamide, and is alcohol-free and fragrance-free.

Best Balancing AHA-BHA: Tarte Knockout Tingling Treatment

Tarte

Tarte Knockout Tingling Treatment acts as an exfoliating, balancing and pore-minimizing solution for most skin types. It may smell a little vinegary, but features a 10% acid complex made up of gentle lactic, citric, malic, phytic and salicylic acids. There’s also niacinamide for brightening and reducing inflammation, glycerin for moisture, and sulfur to reduce the look of pores.

Best Intensive AHA: The Inkey List Glycolic Acid Toner

The Inkey List

The Inkey List Glycolic Acid Toner is a 10% glycolic acid toner that exfoliates surface dead skin cells to improve everything from dullness and rough texture to large pores and fine lines. Since it has a high concentration of the active ingredient, at a low pH level, it’s only meant to be used a few times a week—not daily.

Best Intensive BHA: Paula’s Choice Skin Perfecting 2% BHA Liquid Exfoliant

Paula’s Choice

Paula’s Choice Skin Perfecting 2% BHA Liquid Exfoliant is one of the strongest BHAs, which I’d specifically recommend for oily skin and breakouts. (On other skin types, it will probably be too drying.) It has a silky liquid texture, with 2% salicylic acid at a low pH level.

Best Intensive AHA-BHA: Moon Juice Acid Potion

Moon Juice

Moon Juice Acid Potion is a nightly acid exfoliant that balances 25% AHAs and BHAs with nourishing hydrators. While we’re not told the percentage of each, the acids include glycolic, phytic, lactic and salicylic, and are combined with niacinamide, propanediol, allantoin and mushroom extract.

Best Weekly AHA-BHA Peel: The Ordinary AHA 30% + BHA 2% Peeling Solution

The Ordinary

The Ordinary AHA 30% + BHA 2% Peeling Solution is so strong, you’re only meant to leave it on your skin for 10 minutes, twice a week. There’s 30% AHAs in here—glycolic, lactic, tartaric and citric acids—plus 2% BHAs in the form of salicylic acid. It also has hyaluronic acid, provitamin B5 and Tasmanian pepperberry (which gives it its famous blood-red hue).

Conclusion + Further Reading

Now you know the difference between AHA and BHA exfoliants.

As you may have guessed, I side with Dr. Kligman—I think BHAs are the more beneficial and versatile type of acid, no matter what your skin type.

“AHAs cause smoothing of the skin by removing some of the superficial dead cells, which makes them exfoliants, but that’s all they do. And they don’t begin to compare with salicylic acid, which cleans out the pores.”15

In other words, BHAs do everything AHAs do, and more. So I hope that you’ll consider trying them out, if you haven’t already. You may very well find that your skin is less irritated than it was with AHAs, and of course, less congested. Just be patient if you experience more breakouts initially. Purging simply means that the BHA is doing its job of deep-cleaning, and your skin will become clearer within a few weeks.

Whether you choose an AHA, a BHA or both, the key is to find a formula that is the right strength for your skin, and not overdoing it. While stronger peels are great for instant results (like before a special event), I believe you’ll get the best results from introducing a gentler, low-dose acid on a regular basis—as often as daily.AHA vs BHA: What’s the Difference and How to Choose the Best Acid Exfoliant for Your Skin




 
 
 

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