AHAs and BHAs Sound Like Chemistry Class. Here’s What They Actually Do to Your Skin.

AHA. BHA. Glycolic acid. Salicylic acid. If you’ve ever stood in a skincare aisle (or scrolled through a skincare subreddit at midnight) and felt completely lost — you’re not alone. These terms get thrown around constantly, and nobody ever really explains what they mean in plain English.

Here’s the short version: AHAs and BHAs are both chemical exfoliants, and they are some of the most effective, well-researched ingredients in skincare. They dissolve the “glue” that holds dead skin cells together, which means smoother texture, clearer pores, brighter tone, and fewer breakouts — without any of the friction damage that comes from physical scrubs.

But they work differently. They’re suited to different skin types. And using the wrong one (or the wrong amount) can actually make your skin worse.

Let’s break it all down.

What Are Chemical Exfoliants?

Most of us grew up with physical exfoliants — grainy scrubs, sugar buffs, the little beads in a face wash. The idea is the same: get rid of dead skin cells sitting on the surface so your skin looks fresher and brighter. And it works, kind of. The problem is that scrubbing introduces friction, which can cause micro-tears, irritation, redness, and over time, actual damage to your skin barrier.

Chemical exfoliants skip the friction entirely. Instead of physically scrubbing dead skin off, they use acids (or in some cases, enzymes) to dissolve the bonds that hold those dead cells in place. The cells shed naturally. No rubbing. No micro-tears.

The result is smoother, more even skin — and because you’re not traumatizing the surface, chemical exfoliants are almost always gentler than a gritty scrub when used correctly.

AHAs and BHAs are the two main categories. They’re similar in purpose but behave quite differently once they hit your skin.

What Are AHAs?

AHA stands for alpha hydroxy acid. The most common AHAs you’ll see in skincare are:

• ✦Glycolic acid — the most potent and fastest-acting AHA; small molecule means it penetrates deeply
• ✦Lactic acid — gentler than glycolic, also hydrating; a great starting point for beginners or sensitive skin
• ✦Mandelic acid — the mildest of the three; large molecule, slow-release, excellent for sensitive or reactive skin

AHAs are water-soluble, which means they work at the skin’s surface. They loosen and dissolve dead skin cells on the outer layer — revealing the fresher, brighter skin underneath. They don’t penetrate into pores.

What AHAs are great for:

• ✦Dull, uneven skin tone
• ✦Dry or flaky texture
• ✦Fine lines and early signs of aging
• ✦Dark spots and hyperpigmentation
• ✦Anyone who wants a brighter, more luminous complexion

If your biggest skin concerns are what you see on the surface — texture, dullness, discoloration — AHAs are your answer.

What Are BHAs?

BHA stands for beta hydroxy acid. In skincare, the BHA you’ll almost always encounter is salicylic acid. (There are others, but salicylic is the star.)

Here’s what makes BHAs different: they’re oil-soluble. That means they can cut through sebum — the natural oil your skin produces — and actually penetrate inside your pores. AHAs work on the surface; BHAs go deeper.

Salicylic acid also has a bonus: it’s anti-inflammatory. So it’s not just clearing out congestion — it’s calming redness and swelling at the same time.

What BHAs are great for:

• ✦Blackheads and whiteheads
• ✦Oily or acne-prone skin
• ✦Clogged, congested pores
• ✦Bumpy texture caused by buildup inside the pore
• ✦Hormonal breakouts

If your skin’s main issue is what’s happening inside the pore — oil, congestion, breakouts — BHAs are your move. Salicylic acid is the cornerstone of any acne-fighting routine — here’s how to build one in our skincare routine for acne-prone skin.

AHA vs BHA Side-by-Side

The core difference: AHAs work on the surface, BHAs work inside the pore. Both exfoliate. Both improve texture. But they’re targeting different problems.

Which One Is Right for You?

You don’t need both. Most beginners do best starting with one, nailing the frequency and integration, and then deciding if they want to add the other. Here’s a simple decision guide:

The key rule: pick one, start low, go slow. Exfoliant overload is a real thing, and it looks like redness, dryness, and a broken barrier — exactly the opposite of what you’re going for.

How to Start Using Exfoliants as a Beginner

Ready to add one to your routine? Here’s how to do it without wrecking your skin barrier in the process.

Start with lower percentages: for AHAs, 5–10% is a reasonable starting range. For BHAs, 0.5–2% salicylic acid is plenty. You don’t need a 30% peel to see results. Higher doesn’t mean better — it means a higher chance of irritation.

Common Mistakes Beginners Make

Even with the best ingredients, it’s easy to get this wrong. Here are the biggest pitfalls to avoid:

The Bottom Line

AHAs and BHAs are genuinely game-changing ingredients — but only when you understand what they do and use them correctly. The short version:

• ✦AHAs = surface exfoliation → brightening, smoothing, dark spots, dry/dull skin
• ✦BHAs = pore exfoliation → clears congestion, fights breakouts, oily/acne-prone skin
• ✦Start once or twice a week, low percentage, PM only, SPF every morning
• ✦Don't mix with retinol on the same night, don't layer physical scrubs, don't overdo it

Pick the one that matches your biggest concern. Be consistent. Give it 4–6 weeks. Your skin will tell you when it’s working. For a full timeline of when actives like AHA/BHA start working, see our results guide.

Niacinamide pairs especially well with AHA/BHA — here’s how to layer them the right way so your exfoliant keeps working at its optimal pH.

Best AHA/BHA Picks by Skin Type

Now that you know how AHAs and BHAs work, the next step is finding the right formula for your skin type and experience level. We’ve built out a dedicated picks series with specific product criteria, formula archetypes, and frequency protocols for each skin type.