AHA or BHA? Choose by Your Problem, Not Your Skin Type

Pick an AHA such as glycolic or lactic acid if your main problem is rough texture, dullness or flat dark marks left by old spots. Pick a BHA, which in skincare usually means salicylic acid, if it's blackheads, whiteheads and oily, clogged pores.

Most AHA vs BHA guides sort you by skin type instead: oily gets BHA, dry gets AHA. That chart breaks down if you have oily skin and your real complaint is the brown marks your breakouts leave behind. On medium to deep skin, the wrong acid used too often can add new marks while you're trying to fade the old ones.

So choose by the problem, then check the label for the acid, the strength and the sun warning. Those three things tell you more than the word "exfoliating" on the front.

What's the Difference Between AHA and BHA?

AHAs work on the surface of your skin, while salicylic acid can also work inside oily pores. That's the whole practical difference, and everything else follows from it.

AHA stands for alpha hydroxy acid. The FDA names glycolic acid and lactic acid as the most common AHAs in cosmetics, with citric acid among the others. A 2024 review of lactic acid peels explains that AHAs weaken the links between dead cells in the top layer of skin. Those cells then shed instead of piling up.

Salicylic acid behaves differently because it mixes with oil. A 2015 review of salicylic acid peels calls it a lipid-soluble agent, in contrast with the alpha hydroxy acids such as glycolic acid. That lets it blend with the oily contents of a hair follicle, the stuff that plugs a clogged pore.

The FDA's page on BHAs adds a detail chemists like to point out. Salicylic acid is not a true BHA, though cosmetic companies call it one. On an ingredient list it may also appear as salicylate, sodium salicylate or willow extract.

Which One Do You Need for Your Main Problem?

Match the acid to what you see in the mirror. Your skin type matters for how often you use it, not which one you start with.

• Blackheads, whiteheads, clogged pores: salicylic acid. MedlinePlus says it clears blocked pores and reduces inflammation and redness, so pimples shrink.
• Flat brown marks after breakouts: glycolic acid. The AAD lists it among over-the-counter ingredients that fade dark spots. Salicylic acid isn't on that list.
• Rough, dry or flaky texture: lactic acid. The 2024 review notes it also has some moisturizing properties.
• Sensitive skin that stings easily: lactic acid again, carefully. The 2024 review notes that stinging tests with 10% lactic acid suggest sensitive skin tolerates it well, though it gives few details.
• Red, inflamed acne: salicylic acid helps, but it isn't the best-rated option. More on that below.

The American Academy of Dermatology's 2024 acne guidelines give salicylic acid only a conditional recommendation. Benzoyl peroxide, topical retinoids and topical antibiotics get strong ones.

If salicylic acid hasn't cleared your acne after a fair try, some stronger options are on the pharmacy shelf. Benzoyl peroxide is one, and adapalene gel is sold over the counter too. Others need a prescription.

And not every gray dot on your nose is a blackhead. Some are sebaceous filaments, which refill no matter what, so no acid will clear them for good.

What the Label Tells You That the Front Doesn't

For AHAs, the numbers to find are the percentage and the pH. The FDA's page gives no limit of its own. The figures you'll see quoted come from the Cosmetic Ingredient Review, which the FDA calls the industry's self-regulatory body.

That panel judged glycolic and lactic acid safe at 10% or less, with a final pH of 3.5 or higher. The product should also protect against sun sensitivity or tell you to use daily sun protection. It's a useful line for home products. It's also an industry panel's conclusion, based on industry-sponsored studies, not a promise from a regulator.

The FDA recommends that AHA products carry a "Sunburn Alert" label. It warns that the product may raise your sun sensitivity and your chance of sunburn. It advises sunscreen, protective clothing and limiting sun while you use it and for a week afterward.

If your glycolic toner lists no percentage, you can't tell how strong it is. If it has no sun warning either, the label is skipping what the FDA recommends.

Salicylic acid turns up in both cosmetics and drug products applied to skin, the FDA says. Its BHA page tells you to follow the label and not exceed the recommended number of applications. The industry panel says the product should either contain sunscreen or tell you to use other sun protection. The FDA's own tip is simpler: use sun protection if you use a BHA product.

How Much Do AHAs Raise Sun Sensitivity?

Measurably, and the effect wears off. In an FDA-sponsored study from 2003, volunteers used a cream with AHAs. After four weeks, their skin reddened 18% more easily under UV light.

Sensitivity to UV damage inside skin cells roughly doubled on average, with big differences between people. A week after they stopped, the difference was gone. That matches the "for a week afterward" wording on the Sunburn Alert.

The BHA picture is less clear. The FDA's BHA page reports no results yet, though it notes FDA-initiated studies of salicylic acid and the skin's response to UV. Meanwhile, the industry panel advises makers to test for increased sun sensitivity.

On medium to deep skin, sunscreen matters for a second reason. A clinical review on the NIH bookshelf says daily broad-spectrum sunscreen use should be a foundational part of treating dark marks. UV light can darken them and slow healing.

The AAD says the same thing more bluntly: treatment for dark spots begins with sunscreen. If you've struggled to find one that doesn't leave a cast, this guide to sunscreen on dark skin goes through the options.

Why Over-Exfoliating Leaves Dark Spots on Deeper Skin

Irritation itself can cause dark marks, and deeper skin is more prone to them. The AAD says that when a skin product irritates your skin, it can cause dark spots.

Its exfoliation guide is specific. For some people, especially those with darker skin tones, more aggressive exfoliation can lead to more pigmentation. The AAD advises avoiding strong chemical or mechanical exfoliation if you have a darker skin tone. The same applies if you get dark spots after burns, bug bites or breakouts.

The NIH bookshelf review explains why the stakes are higher. Post-inflammatory hyperpigmentation (PIH) is the medical name for these marks, and it's more common and severe in darker skin tones. Tan to dark brown marks near the surface usually fade or improve a lot within 6 to 12 months. Blue-gray marks sit deeper, improve slowly and may be permanent.

So a week of stinging from a too-strong acid can cost you most of a year. That's why the order matters. Calm skin first, then fade the marks.

What the Research on Peels Shows

A 2024 systematic review looked at treatments for PIH in skin of color. Glycolic acid had the better results. In a 1997 study of 25 patients included in the review, repeated glycolic peels cut a pigment severity score by half over 22 weeks.

Salicylic acid did worse. Two small studies of 20% to 30% salicylic peels, 11 patients in all, reported some improvement, but none that was clearly significant. In one of them, 40% of patients had new hyperpigmentation two weeks after the peel. The authors also found that "chemical peels exhibited increased adverse effects, specifically with SA."

These were clinic peels, many times stronger than a salicylic face wash. Don't read them as a reason to throw out your cleanser. But they do back the choice above: for dark marks, glycolic acid is the acid with the better evidence. The review's authors were blunt about the field overall, finding "a lack of robust efficacy" across every treatment they looked at.

The older 2015 review had called salicylic peels safer for darker skin, based on one study of 25 patients. The newer review weighed more treatments and reached a more cautious view. For the full side-by-side on retinoids, azelaic acid and the rest, see how to use actives on dark skin without new marks.

How to Start Without Making New Marks

• Start with one acid, on a few nights a week, at a home strength. The AAD's rule is that the more aggressive the exfoliation, the less often you need it.
• Patch test first. The FDA suggests trying any BHA product on a small area before using it widely.
• Stop, and see a doctor, if irritation or stinging lasts. On deeper skin, that redness is the warning sign, not something to push through.
• Moisturize right after, and never exfoliate over cuts, open wounds or sunburn.
• Skip at-home peels unless a dermatologist has said yes.

If you already have a tight, stinging face, the signs of over-exfoliating and how to recover will tell you what to stop first.

Can You Use AHA and BHA Together?

Yes, but not stacked in the same spot on the same night when you're starting out. A common split is salicylic acid on an oily T-zone and a gentle AHA on drier cheeks, or the two on different nights.

Watch the rest of your routine too. The AAD says exfoliating while you use prescription retinoids, retinol or benzoyl peroxide may worsen dry skin or even cause breakouts. MedlinePlus says to avoid abrasive cleansers, alcohol-based products, benzoyl peroxide, resorcinol, sulfur and tretinoin on skin you treat with salicylic acid, unless your doctor says otherwise.

Most of those clashes are about irritation adding up, not one ingredient destroying another. The skincare ingredients that really cancel each other out sorts the real conflicts from the myths.

Is Salicylic Acid Safe in Pregnancy?

For a face product, it's generally considered safe. A 2023 review of acne treatment in pregnancy says topical salicylic acid is considered safe during all trimesters and while breastfeeding. The reason is that so little reaches the bloodstream. It advises against using it over large areas for long periods or under airtight (occlusive) dressings.

The same review calls glycolic and lactic acid peels safe in pregnancy and breastfeeding, because they don't penetrate far. It says most experts recommend avoiding all topical retinoids while pregnant. MedlinePlus still asks you to tell your doctor if you're pregnant, planning to be or breastfeeding before you use salicylic acid.

Don't use BHA products on babies or children, the FDA advises. MedlinePlus adds that children and teens with chickenpox or flu shouldn't use it without a doctor's approval, because of the risk of Reye's syndrome.

When to See a Doctor

Check with your doctor before starting salicylic acid if you have diabetes, or blood vessel, kidney or liver disease. Mention it too if you take aspirin or use muscle rubs with methyl salicylate. MedlinePlus also says not to put it on large areas of your body unless your doctor says you should.

MedlinePlus lists emergency symptoms with salicylic acid. Stop the product and get help right away for hives, itching, throat tightness, trouble breathing or feeling faint. The same goes for swelling of your eyes, face, lips or tongue. Call 911 (999 in the UK) or your local emergency number.

Call your doctor right away if you get ringing in your ears, hearing loss, confusion, dizziness, headache or fast breathing while using salicylic acid. MedlinePlus also lists extreme tiredness or weakness, nausea, vomiting and diarrhea as serious side effects.

If someone swallows a salicylic acid product or puts on too much, call Poison Help at 1-800-222-1222 in the US, free and 24/7. If the person has collapsed or isn't breathing, call 911.

See a dermatologist if your acne hasn't improved with home products or acids leave you red and raw. Go too if dark marks look blue-gray rather than brown. Those deeper marks are the slowest to improve. Ask whether a retinoid or benzoyl peroxide would suit you, and ask for someone experienced with your skin tone before any peel.

Frequently Asked Questions

Is AHA or BHA Better for Acne?

BHA, meaning salicylic acid, is the better fit for blackheads and whiteheads because it works inside oily pores. For acne overall, the AAD's 2024 guidelines give benzoyl peroxide, topical retinoids and topical antibiotics strong recommendations. Salicylic acid gets only a conditional one.

Which Is Better for Dark Spots, AHA or BHA?

An AHA, usually glycolic acid. The AAD lists glycolic acid among ingredients that fade dark spots. The 2024 review also found better results for glycolic peels than salicylic peels on skin of color. Use it gently, with daily sunscreen, because irritation can make new marks.

How Long Does It Take for AHA to Fade Dark Spots?

Expect months, not weeks. The AAD says a spot a few shades darker than your skin usually fades within 6 to 12 months, and deeper color can take years. Glycolic acid and daily sunscreen can help it along.