AHA vs BHA
Two families of exfoliating acid that do different jobs: AHAs work on the surface for tone and texture, BHA gets into pores for oil and breakouts. Here's how to choose.
Chemical exfoliants come in two families, and picking the wrong one is why a lot of people decide “acids don’t work for me.” The split is simple once you know it: AHAs are water-soluble and work on the surface, while BHA is oil-soluble and works inside the pore. That single difference in chemistry decides which one suits your skin and your goal.
AHAs: surface tone and texture
Alpha hydroxy acids — most commonly glycolic and lactic acid, with gentler mandelicacid as a third option — are water-soluble. They work at the skin’s surface, loosening the bonds between dull, dead cells so they shed more evenly. The result is brighter, smoother, more even-looking skin, which is why AHAs are the go-to for dullness, rough texture, uneven tone and sun damage. Glycolic is the smallest molecule and the most potent; lactic is a touch gentler and more hydrating; mandelic is the largest and slowest, which makes it the friendliest for sensitive skin.
BHA: pores, oil and breakouts
There’s really one BHA in skincare: salicylic acid. Because it’s oil-soluble, it can cut through the sebum in a pore and exfoliate from the inside, clearing the clogs that turn into blackheads and breakouts. That makes it the obvious pick for oily, congested and acne-prone skin. It’s also mildly anti-inflammatory, so it calms the look of active blemishes as well as preventing new ones. Our salicylic acid guide goes deeper on strengths and how to work it in.
Head to head
| AHA (glycolic, lactic, mandelic) | BHA (salicylic acid) | |
|---|---|---|
| Solubility | Water-soluble — works on the surface | Oil-soluble — works inside the pore |
| Best for | Dullness, texture, uneven tone, dryness | Oily skin, blackheads, congestion, breakouts |
| Skin type | Normal, dry, sun-damaged | Oily, combination, acne-prone |
| Gentlest option | Mandelic acid | Lower-percentage (0.5–2%) leave-ons |
| Sun sensitivity | Increases it — SPF required | Less than AHAs, but still wear SPF |
How to choose — and use them safely
Start from your skin. Dry, dull or uneven? Reach for an AHA. Oily, congested or breakout-prone? Reach for a BHA. Sensitive but curious? Begin with mandelic acid or a low-strength salicylic and build up slowly. Combination skincan genuinely use both — a BHA on the oily T-zone and an AHA on the drier areas or on alternate nights.
Whichever you pick, the safety rules are the same. Introduce one acid at a time, start at a couple of nights a week, and don’t layer it with retinol on the same night — that’s the fastest route to an over-exfoliated, stinging barrier (see our layering matrix). And because exfoliating acids make skin more sun-sensitive — the FDA notes the effect can last about a week — daily sunscreen isn’t optional. When you’re ready to buy, our best chemical exfoliants roundup lines up real products by acid type.
General guidance, not medical advice. Barrier & Balm 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 and work on the skin's surface, loosening dead cells to improve tone, texture and dullness. BHA (beta hydroxy acid — salicylic acid) is oil-soluble, so it penetrates into oily pores to clear congestion and breakouts. In short: AHA for surface tone and texture, BHA for pores and oil.
Should I use AHA or BHA?
Match the acid to your skin. Choose an AHA (glycolic, lactic or gentle mandelic) if your goals are brightness, smoother texture, uneven tone or dryness. Choose BHA (salicylic acid) if you have oily, congested or acne-prone skin, blackheads, or clogged pores. Combination skin can use both — a BHA on the oily T-zone, an AHA elsewhere.
Can I use AHA and BHA together?
You can, but be cautious. Some products combine them, and using them on alternating nights is a common approach. The risk is over-exfoliation — stinging, redness and a compromised barrier — so start with one, use it a couple of nights a week, and only add the second once your skin is comfortable. Don't stack them with retinol on the same night.
Do exfoliating acids make you more sensitive to the sun?
Yes. The FDA notes that AHAs can increase sun sensitivity and the risk of sunburn, and the effect can persist for about a week after you stop using them. Daily broad-spectrum sunscreen is non-negotiable with any exfoliating acid — both to protect the fresh skin and to avoid undoing the tone improvements you're after.
Sources
- U.S. FDA — Alpha Hydroxy Acids — FDA on AHAs and increased sun sensitivity (accessed July 17, 2026)
- U.S. FDA — Beta Hydroxy Acids in Cosmetics — FDA on salicylic acid as a beta hydroxy acid (accessed July 17, 2026)
- Chemical Peels for Skin Resurfacing — StatPearls (NCBI Bookshelf) — Reference overview of AHA/BHA exfoliation mechanisms (accessed July 17, 2026)
Keep reading
Physical vs chemical exfoliation
The bigger fork before the acids — scrub it off or dissolve it off, and which is gentler.
Compare the methodsLactic acid vs glycolic acid
Zoom in on the AHAs — which of the two surface acids suits your skin.
Compare the acidsGlycolic acid, explained
The strongest AHA in depth — what it does and how to use it safely.
Read the guideBest chemical exfoliants
AHAs and a BHA compared by acid type — the real products, from gentle mandelic to a leave-on salicylic.
See the picksSalicylic acid, explained
The BHA in depth — how it clears pores, the strengths that matter, and who should use it.
Read the guideBest skincare for acne-prone skin
Where a BHA fits alongside the other ingredients with real acne evidence.
See the guideWhat not to mix with retinol
Acids plus retinol on the same night is a common over-exfoliation trap — the layering matrix.
Check the matrix