Exfoliating Acids (AHA / BHA)

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.