Actives & Acids

Exfoliating Acids (AHA / BHA)

Glycolic, salicylic, azelaic, mandelic and lactic acid — which acid does what, at what strength and pH, and how to exfoliate without wrecking your barrier.

Chemical exfoliants dissolve the bonds holding dead cells on the surface of your skin, so instead of scrubbing them off with grit you let an acid loosen them evenly. Done right, that means smoother texture, a brighter tone, clearer pores and better product absorption. Done wrong — too strong, too often, or stacked on top of everything else — it means a stripped, stinging, over-exfoliated barrier. The whole game is matching the right acid, at the right strength, to your skin and your goal.

This hub sorts the acid aisle out. Below you’ll find our overall chemical-exfoliant roundup plus dedicated picks for glycolic, salicylic and azelaic acid, the plain-English AHA vs BHAexplainer, a head-to-head between the two most-searched acids, and a full glossary of every acid in one place. Start with the main roundup if you want one bottle to begin with, or read the explainer first if the alphabet soup of acids is what’s stopping you.

Everything in Acids

How to choose an exfoliating acid

Match the acid to the job. AHAs(alpha hydroxy acids) like glycolic and lactic are water-soluble and work on the surface — best for dullness, rough texture and uneven tone. BHA (salicylic acid) is oil-soluble, so it gets inside the pore — best for blackheads, congestion and oily, acne-prone skin. Azelaic and mandelicacid are the gentle multitaskers for redness, bumps and sensitive skin. If you don’t know where to start, our best chemical exfoliants roundup names the one most people should reach for first, and glycolic vs salicylic settles the most common decision: glow and tone versus blackheads and oil.

What decides the price and the cost-per-mL

With acids, the number on the front is only half the story — the pH and the exact acid decide how much of that percentage is actually active. A 7% glycolic toner at a low, effective pH can out-work a 10% at a sloppy one, which is why we read the stated percentage and note pH where a brand publishes it. Price mostly tracks format and base, not potency: a simple toner is cheap per milliliter, a leave-on gel or serum with added soothers costs more, and a weekly high-strength peel is priciest per bottle but you use it rarely, so its cost-per-usecan be low. Work out cost-per-mL, then adjust for how often you’ll actually use it — a daily toner and a once-a-week peel are not the same math.

The mistake buyers make

Over-exfoliating is the number-one error. More acids, higher percentages, and daily use do not equal better skin — they equal a compromised barrier that stings, flakes and breaks out, which people often mistake for “not exfoliating enough” and then double down on. Start with one acid, two or three times a week, and build from there. The second mistake is stacking acids with retinol or benzoyl peroxide the same night when you’re starting out; alternate them on separate evenings instead. And because AHAs increase sun sensitivity, daily sunscreen is part of the deal, not optional. If you want to go deeper on which molecule does what, our acids explained glossary lists every AHA, BHA and PHA with how strong is too strong.

How to know you’re over-exfoliating

Your skin will tell you long before real damage sets in, if you know the signs. Early warnings are a tight, shiny, waxy look, stinging when you apply anything (even plain moisturizer or water), and skin that feels dehydrated no matter how much you hydrate it. Push further and you get persistent redness, small flaky patches, and breakouts that don’t behave like your usual ones — often misread as “not exfoliating enough,” which sends people the exact wrong direction. If any of that shows up, stop all acids and retinol, drop back to a gentle cleanser, a bland moisturizer and sunscreen, and let the barrier recover for a week or two before reintroducing anything. When you come back, come back slower and with one acid, not three. The goal is smoother skin, not the most aggressive routine you can tolerate on a good day.

Frequently asked questions

What's the difference between AHA and BHA?

AHAs (like glycolic and lactic acid) are water-soluble and work on the skin's surface — best for dullness and rough texture. BHA (salicylic acid) is oil-soluble and gets inside pores — best for blackheads, congestion and oily, acne-prone skin.

Which exfoliating acid should a beginner start with?

For most people, one gentle acid used two or three times a week: a low-strength glycolic or lactic AHA for texture and tone, or salicylic (BHA) if your main concern is clogged pores and oiliness. Mandelic or azelaic acid suit sensitive skin.

How often should I use an exfoliating acid?

Start two or three times a week and only increase if your skin stays comfortable. Daily use suits some people once tolerant, but over-exfoliating — stinging, flaking, new breakouts — means you're using it too strong or too often. Ease off, don't push through.

Do exfoliating acids make you more sensitive to the sun?

AHAs increase sun sensitivity, so daily broad-spectrum sunscreen is essential when you use them — both to protect newly exposed skin and to keep the tone-evening results you're working for. BHA is less of an issue, but SPF is still smart.

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