AHA vs BHA: which exfoliating acid is right for your skin?

Key takeaways

• AHAs (like glycolic and lactic acid) are water-soluble and work mainly on the surface of the skin. BHAs (mainly salicylic acid) are oil-soluble, so they can get into pores.

• AHAs tend to suit dry, dull or sun-damaged skin. Salicylic acid tends to suit oily skin, blackheads and whiteheads.

• In an FDA study, four weeks of AHA use raised skin’s sensitivity to UV reddening by 18%. Wear sunscreen daily with either acid.

• You can use both, but start with one, go slowly and avoid stacking them when you’re new to acids.

• PHAs, like gluconolactone and lactobionic acid, are a newer, gentler option for sensitive skin.

What are AHAs and BHAs?

Both are exfoliating acids. Cleveland Clinic explains that face acids “work to turn over layers of dead skin cells quicker than would happen on their own.” The difference is in how they dissolve.

• AHAs (alpha hydroxy acids) are water-soluble. Cleveland Clinic says they “loosen the fluid that binds surface skin cells together,” so dead skin can slough off. The most common in skincare are glycolic acid, from sugarcane, and lactic acid, from milk. Others include citric, malic and tartaric acid.

• BHAs (beta hydroxy acids) are oil-soluble. Cleveland Clinic says they “penetrate deeper into your pores than AHAs” and also help dissolve sebum, the oil that can lead to acne. In skincare, BHA almost always means salicylic acid.

One quirk: the FDA notes that “from a chemist’s perspective, salicylic acid is not a true BHA,” but the name has stuck.

AHA vs BHA: the key differences

• Where they work. AHAs work mostly on the surface. Salicylic acid can mix with the oils in pores and hair follicles, so it reaches clogs AHAs don’t.

• What they’re best at. AHAs help with dullness, uneven tone, dark spots and dry, rough texture. BHAs help with blackheads, whiteheads and oily skin.

• Strength. Glycolic acid is the smallest AHA, and Cleveland Clinic says it can penetrate deeper than other AHAs and “can be very strong and irritating.” Lactic acid is one of the gentler AHAs and also moisturizes.

• Regulation. In the US, salicylic acid is also an over-the-counter acne drug. The FDA’s acne rules allow it at 0.5% to 2%.

Which should you choose?

Choose an AHA if your skin is dry, dull or showing sun damage. DermNet says AHA products are recommended for skin showing signs of aging, and that fine lines and brown marks can improve with regular use. Cleveland Clinic lists more even-looking skin tone and lighter dark spots from mild sun damage or acne among glycolic acid’s benefits.

Choose a BHA if your skin is oily or you get blackheads and whiteheads. The American Academy of Dermatology (AAD) says salicylic acid “works best on whiteheads and blackheads” because it unclogs pores and exfoliates. Cleveland Clinic adds that it isn’t overly irritating for most people. Our list of face washes for acne includes several salicylic acid cleansers.

Go gently if your skin is sensitive. Cleveland Clinic advises caution with glycolic acid if you have sensitive or dry skin, rosacea or eczema. Lactic acid or a PHA is usually an easier starting point.

What about PHAs?

Polyhydroxy acids (PHAs) are a newer generation of these acids. The two you’ll see most are gluconolactone and lactobionic acid. In a review of hydroxy acids, a 77-volunteer study found lactobionic acid caused less irritation and less disruption to the skin barrier than matching glycolic acid formulas. They’re often suggested for sensitive skin.

Side effects and sun sensitivity

Both types can sting, turn skin red or irritate it, especially at higher strengths or on broken skin. Cleveland Clinic warns that too much “can also be irritating because you’re essentially stripping the top layer of your skin.”

AHAs also make skin more sensitive to the sun. The FDA reports that after four weeks of AHA use, volunteers’ sensitivity to UV reddening rose by 18%, and their sensitivity to UV-induced cellular damage doubled on average. The effect was reversible: a week after stopping, the difference was gone. The FDA suggests AHA products carry a sunburn alert telling you to use sunscreen, wear protective clothing and limit sun exposure while using them and for a week afterward.

For BHAs, the FDA advises testing a product on a small area first, stopping if you get irritation or prolonged stinging, avoiding BHA products on infants and children, and using sun protection.

For everyday products, an expert safety panel the FDA cites found glycolic and lactic acid safe at 10% or less, at a pH of 3.5 or higher, with sun protection. Stronger salon peels are meant for trained professionals.

If you’re pregnant, the American College of Obstetricians and Gynecologists lists topical salicylic acid and glycolic acid among over-the-counter acne ingredients that can be used during pregnancy. Check with your doctor first.

Can you use AHA and BHA together?

Yes, but not all at once when you’re starting out. Cleveland Clinic suggests avoiding glycolic acid alongside other exfoliants, like lactic and salicylic acid, at first, and advises that you “use just one product for a bit and see how you react before adding another.”

A few ways to combine them once your skin is used to acids:

• Alternate nights. Use a BHA one evening and an AHA another.

• Split by area. Use a BHA on an oily T-zone and an AHA on drier cheeks.

• Start slowly. Cleveland Clinic suggests starting glycolic acid once or twice a week and building up from there.

Our guide to how often to exfoliate covers how to space them out, and if you also use a retinoid, our guide to retinol for beginners explains how to ease in.

How to use exfoliating acids

• Apply at night. DermNet notes leave-on AHA products should go on at night. Our list of the best face exfoliators compares BHA, AHA and PHA options.

• Wear sunscreen every morning. Cleveland Clinic says SPF 30 or higher is vital because acids expose fresh skin. Our guide to mineral vs chemical sunscreen explains the options.

• Moisturize. Acids can dry skin, and the AAD recommends a gentle daily moisturizer with acne ingredients like salicylic acid.

• Watch for early breakouts. A few small pimples can show up when you start an acid. Our guide to skin purging explains how to tell it from a reaction.

Frequently asked questions

Is salicylic acid an AHA or BHA?

It’s a BHA, and it’s by far the most common one in skincare. The FDA notes that chemically it isn’t a true BHA, but that’s the name it goes by.

Which is better for clogged pores, AHA or BHA?

BHA. Salicylic acid is oil-soluble, so it can work inside pores, and the AAD says it works best on whiteheads and blackheads. Our guide to minimizing the look of pores covers more options.

Do AHAs make your skin more sensitive to the sun?

Yes. An FDA study found four weeks of AHA use raised sensitivity to UV reddening by 18%, though it went back to normal within a week of stopping. Wear sunscreen every day while using them.

Can you use AHA and BHA every day?

Some people can, but it’s best to start with one acid a couple of times a week and build up. If your skin stings, turns red or feels tight, cut back.

Do I need both an AHA and a BHA?

No. Many people do well with just one. Pick the one that matches your main concern, and add the other only if you need it and your skin tolerates it.