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Is glycolic acid an AHA? Which acid is which
Yes, glycolic acid is an AHA. So is lactic acid. Salicylic acid is the BHA, and in skincare it is effectively the only one. Benzoyl peroxide is neither, because it is not a hydroxy acid at all.
AHA stands for alpha hydroxy acid and BHA for beta hydroxy acid. The alpha and the beta describe where one part of the molecule sits, which sounds like trivia and turns out to matter: it is why AHAs are water-loving surface acids and salicylic acid is oil-soluble, and therefore why they suit different skin. The full table is below.
The whole shelf, sorted
If you only want the answer to "which family is this bottle in", this table has it. Strengths are the usual over-the-counter cosmetic ranges, not professional peel strengths, which run far higher and are a different thing entirely.
| Ingredient | Family | Usual OTC strength | Tends to suit |
|---|---|---|---|
| Glycolic acid | AHA | 5 to 10 % | Rough-looking texture and dullness. The briskest of the AHAs, and the most likely to sting. |
| Lactic acid | AHA | 5 to 10 % | The same jobs as glycolic, more gently. A bigger molecule, so it tends to feel milder at the same percentage. |
| Mandelic acid | AHA | varies widely by product | The gentlest-feeling of the three, and the least documented. Often chosen by people who found glycolic too much. |
| Salicylic acid | BHA | 0.5 to 2 % | Oilier skin, visible pores and non-inflamed congestion. Oil-soluble, which is the whole reason it suits those areas. |
| Gluconolactone, lactobionic acid | PHA | varies widely by product | A third, gentler family. Larger molecules again, marketed for reactive skin. |
| Benzoyl peroxide | Neither | 2.5 % is the usual start | Inflamed, angry-looking breakouts. Not an exfoliating acid and not in this family at all. |
| Azelaic acid | Neither | around 10 % over the counter | An acid by name that does not exfoliate like an AHA or BHA. Notably well tolerated by reactive skin. |
| Ascorbic acid (vitamin C) | Neither | 10 to 20 % | An acid by name and a morning brightening active by job. Not an exfoliant. |
| Hyaluronic acid | Neither | n/a | An acid by name only. It is a humectant. It does nothing exfoliating whatsoever. |
The bottom four rows exist because "acid" in a name means almost nothing. Hyaluronic acid, ascorbic acid and azelaic acid are all acids, and none of them behaves like the acid you are thinking of when you say "should I use an acid tonight".
Is benzoyl peroxide an AHA or a BHA?
Neither, and it is worth being specific about why, because this one gets asked a lot. Benzoyl peroxide is a peroxide. It has no hydroxy acid structure, it is not an exfoliant, and it follows different rules in a routine: it does not increase sun sensitivity the way AHAs do, but it does bleach towels and pillowcases, which no AHA does.
People conflate it with salicylic acid because both turn up in products aimed at breakouts. They suit different looks. Benzoyl peroxide tends to suit inflamed, angry spots; salicylic acid tends to suit calmer congestion and visible pores. And benzoyl peroxide has its own layering rules, covered in the guide on benzoyl peroxide and retinol.
"Glycolic vs AHA" is not a comparison
People search this, so it is worth saying plainly: glycolic acid is an AHA, in the same way a labrador is a dog. There is nothing to compare.
The comparison that does mean something is glycolic against lactic, since those are the two AHAs you will actually choose between in a shop.
Glycolic, lactic or salicylic: which should you pick?
| Glycolic acid | Lactic acid | Salicylic acid | |
|---|---|---|---|
| Family | AHA | AHA | BHA |
| Solubility | water-loving, works on the surface | water-loving, works on the surface | oil-soluble, suits oilier areas |
| Pick it for | dull, rough-looking texture | the same, with a milder feel | visible pores, congestion, oilier skin |
| Feel | the briskest, most likely to sting | gentler, leans hydrating | can be drying if overused |
| Usual strength | 5 to 10 % | 5 to 10 % | 0.5 to 2 % |
| Sunscreen | non-negotiable | non-negotiable | sensible, and less critical than with AHAs |
A blunt rule that gets most people to the right bottle: if your complaint is texture and dullness, take an AHA. If your complaint is oiliness and congestion, take the BHA. If you are new to acids entirely, start with lactic acid rather than glycolic, twice a week, and see what your skin says.
Can you use AHA and BHA together?
Not in the same layer, no. Two acids at once is the most reliable way to end up with a tight, stinging face and then swear off acids altogether. Alternate them on different evenings instead. Some products do combine them at low strengths and are formulated for it, which is a different situation from you stacking two separate bottles.
The same logic applies to acids next to other strong actives: keep an acid away from a retinoid on the same night, and away from pure vitamin C in the same layer.
The one rule with AHAs that is not optional. AHAs make skin more sensitive to sunlight. Sunscreen every morning while you use them, SPF 30 or higher, no exceptions. Using an AHA without daily sunscreen is working against yourself, and it is the single most common way people undo months of their own effort.
How often, and how long before anything shows?
Two evenings a week is a sensible starting frequency for any of these, going up only if your skin is comfortable. Daily acid use is rarely the right answer, and never the right starting answer.
On timing: a smoother, brighter-looking surface tends to show up within one to two weeks, because that part is surface-level. Texture takes longer, in the range of four to eight weeks. Anything described as happening deeper than that is a months-long project. Those are orders of magnitude rather than promises, and they assume you use the thing consistently and wear sunscreen.
How Baselit handles acids
Baselit builds routines from a selfie and treats acids as evening steps by default, with sunscreen mandatory in the morning alongside them. New users are capped at one irritating active at a time, so you will not get an AHA and a retinoid handed to you in the same week, and the app will not recommend a product whose second active collides with an acid you are already on.
If you are standing in front of a shelf trying to work out which family a bottle belongs to, that is also what the product check answers: photograph it or scan the barcode, and you get the ingredient list plus whether it fits the routine you are already running or duplicates a slot you have filled.
Frequently asked questions
Is glycolic acid an AHA?
Is salicylic acid a BHA?
Is lactic acid an AHA?
Is benzoyl peroxide an AHA or a BHA?
What is the difference between glycolic acid and AHA?
Is azelaic acid an AHA or BHA?
Can I use AHA and BHA together?
Do I need sunscreen with AHAs?
Baselit is a cosmetic skin-analysis app, not medical advice. This guide sorts ingredients by chemical family and describes what they do for the look and feel of skin. It is not a diagnosis or a treatment, and it is no substitute for a doctor or dermatologist.