Actives & Acids

AHA vs BHA: Which Exfoliating Acid Is Right for You

One is water-soluble and works on the surface; the other is oil-soluble and gets inside pores. Match the chemistry to your skin — surface and tone, or oil and congestion — and add a note on gentle PHAs.

By Stephen V.Last updated How we pick

“Chemical exfoliation” sounds intense, but the choice underneath it is simple once you know the trick. Exfoliating acids split into two camps defined by one property: whether they dissolve in water or in oil. That single difference decides where each acid works and, in turn, which skin and which problem it’s best for. AHAs are water-soluble and work on the surface. BHA is oil-soluble and gets inside pores. Get that straight and picking the right acid stops being a guessing game.

AHAs: water-soluble, surface and tone

AHA stands for alpha hydroxy acid, a family that includes glycolic, lactic, and mandelic acids. Because they’re water-soluble, they work across the surface of the skin, loosening the bonds that hold dull, dead cells together so they shed more evenly. The payoff is smoother texture, brighter and more even tone, and over time a softening of fine lines and the look of sun damage. The three you’ll meet most often line up neatly by molecule size, which tracks with strength and sting:

  • Glycolic acidis the smallest molecule, so it penetrates fastest and hits hardest. It’s the most powerful common AHA for glow and resurfacing — and the most likely to sting if you overdo it.
  • Lactic acid is a larger molecule that works a little more gently and brings some hydrating character, which makes it a friendlier AHA for skin that finds glycolic too much.
  • Mandelic acidis larger still, so it penetrates slowest and is the gentlest of the three — a good AHA for sensitive skin or a cautious start.

One thing the FDA is explicit about: AHAs can make skin more sensitive to the sun. That makes daily sunscreen part of the deal, not an afterthought, whenever an AHA is in your routine.

BHA: oil-soluble, pores and oil

BHA means beta hydroxy acid, and in skincare it’s essentially one ingredient: salicylic acid. Its defining trait is that it’s oil-soluble, so unlike the AHAs it can cut through the oil in a pore and exfoliate from inside it. That is exactly why it’s the go-to for oily, congested, breakout-prone skin: it clears out the plugs of dead cells and sebum behind blackheads and whiteheads, and it has a calming, anti-inflammatory character that suits acne-prone skin. Salicylic acid is commonly used at up to 2% in leave-on products, and it’s the acid to reach for when the problem is coming from your pores rather than sitting on the surface. If surface dullness is an AHA problem, clogged and oily is a BHA problem.

A note on PHAs

There’s a gentler third option worth knowing: PHAs, or polyhydroxy acids, such as gluconolactone. They exfoliate by the same broad mechanism as AHAs but their molecules are larger, so they penetrate more slowly and tend to be kinder to sensitive, reactive, or easily irritated skin. PHAs won’t resurface as assertively as glycolic acid, and that’s the point — they’re the low-and-slow entry ramp for people who want the benefits of chemical exfoliation without the bite. If even mandelic or lactic acid feels like too much, a PHA is a sensible place to start.

AHA vs BHA at a glance

AHA compared with BHA across solubility, where it works, best skin and best concern
 AHA (glycolic, lactic, mandelic)BHA (salicylic)
SolubilityWater-solubleOil-soluble
Where it worksOn the skin’s surfaceInside oily pores
Best forDullness, uneven tone and texture, fine lines, sun damageBlackheads, whiteheads, oiliness, clogged pores
Best skin typeNormal, dry, sun-damaged, tone-focusedOily, combination, congestion- and acne-prone
Gentle option in the familyMandelic or lactic (or step down to a PHA)Lower-strength salicylic; less-frequent use
Sun sensitivityBoth call for daily sunscreen; AHAs are specifically flagged for increasing sun sensitivity.

Use an AHA if…

  • Your main concerns are dullness, uneven tone, rough texture, or early fine lines.
  • Your skin is normal, dry, or sun-damaged rather than oily and congested.
  • You want overall glow and smoothness across the whole face, not pore-specific cleanup.
  • You’re sensitive — in which case start with mandelic or lactic acid, or a PHA.

Use a BHA if…

  • You’re oily or combination and prone to congestion.
  • Your issue is blackheads, whiteheads, and clogged pores.
  • You have breakout-prone skin and want an acid with a calming, anti-inflammatory bent.
  • You want to target the T-zone or specific congested areas rather than resurface everywhere.

The verdict

AHAs work on the surface for tone and texture; BHA gets inside pores for oil and congestion — so let your main concern and your skin’s oiliness decide. Dry or sun-damaged skin chasing glow leans AHA; oily, breakout-prone skin leans BHA; sensitive skin should start gentle with mandelic, lactic, or a PHA. You don’t need both to start, and whichever you choose, go slow, a couple of nights a week, and wear sunscreen daily. For where to buy, see our best chemical exfoliants roundup, and if you want the two headline acids head-to-head, read glycolic acid vs salicylic acid.

General guidance, not medical advice. Actives & Acids is written by a skincare enthusiast, not a dermatologist. For a diagnosis, a reaction, or a prescription active like tretinoin, see a qualified professional. Introduce any new active slowly and patch-test first.

Frequently asked questions

What's the difference between AHA and BHA?

AHAs (alpha hydroxy acids, like glycolic and lactic) are water-soluble, so they work mainly on the skin's surface to loosen dead cells and even out tone and texture. BHA (beta hydroxy acid, meaning salicylic acid) is oil-soluble, so it can get down into oily pores to clear congestion. Surface and tone versus pores and oil is the simplest way to remember it.

Can I use an AHA and a BHA together?

You can, but you don't need both every day, and combining them raises the odds of over-exfoliating. A common approach is to alternate nights, or use a BHA on oily and congested areas and an AHA elsewhere. If your skin is new to acids, start with one, a couple of times a week, and build slowly.

Do exfoliating acids make skin more sun-sensitive?

Yes — the FDA notes that AHAs can increase sun sensitivity, and the same caution is wise with any chemical exfoliant. Daily broad-spectrum sunscreen isn't optional when you exfoliate; without it you can trade rough texture for new sun damage and undo the tone work you're trying to do.

What is a PHA, and who is it for?

PHAs (polyhydroxy acids, like gluconolactone) are larger molecules that penetrate more slowly and gently than AHAs, so they tend to be better tolerated by sensitive or reactive skin. Think of them as a lower-and-slower entry point: gentler exfoliation for people who find even lactic acid too much.

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