What Exactly Is the Difference Between AHAs and BHAs?

Let’s talk acid.

If you forget to wipe down furniture, it acquires dust. It might not be that noticeable, but it's there and dulls the room. Well, your skin kind of works the same way. Cleansing and moisturizing alone won't give you a glow—what your skin care routine needs are hard-working alpha-hydroxy acids (AHAs) and beta-hydroxy acids (BHAs) to dissolve the gunky layer on top of your skin. By breaking down sebum (that oily and waxy excretion) and loosening dead skin cells, new skin cells pave the way to a dewier complexion.

So what exactly are AHAs and BHAs? You might envision a chemical peel or a fancy exfoliation treatment at the dermatologists office, but that's not necessarily the case. Skincare experts swear that adding at-home products with AHAs and BHAs to your daily skincare routine can make a difference in as little as three weeks.

We consulted top dermatologists to break down everything you need to know about how these anti-aging wonder molecules help with acne, fine lines, and sun spots.

What are AHAs?

AHAs are typically derived from sugars. The ever-popular glycolic acid can be derived from sugar cane and pineapple. Lactic acid is an offspring of fermented dairy like yogurt—legend has it, Cleopatra owed her youthful beauty to sour milk baths. Other, milder AHAs include citric acid from citrus fruits, malic acid from apples and blueberries, mandelic acid from almonds, and tartaric acid from grapes and tamarinds. Because these acids come from fruit, some dermatologists believe they also pass down their antioxidant properties to deal with pollution that can rob skin of its glow. What's more, your skin is likely to be less oily within days of starting the AHA.

The primary job of AHA is to help with skin peeling. (Don't worry, not the post-sunburn kind of peeling.) "AHAs stimulate new cell generation, resulting in improved skin texture and a brighter complexion," says Ellen Marmur, MD, a board-certified dermatologist in New York City and founder of MMSkincare.

Products with AHA aim to minimize age spots and discoloration from UV damage. Studies show that pairing products with glycolic or lactic acid along with sunscreen reduces fine lines around your eyes better than relying on sunscreen alone.

"I recommend that everyone consider incorporating at least one AHA product into their weekly regimen starting at the age of 20 as both a preventative and a corrective," says Loretta Ciraldo, MD, a board-certified dermatologist in Miami and founder of Dr. Loretta Skincare.

What are BHAs?

You may not realize it, but you probably already have a BHA product in your bathroom cabinet—it's salicylic acid. Salicylic acid's gentler cousin, betaine salicylate, stars in mask and cream formulas.

Your pores are kind of like a landfill (sorry, but it's true!), and salicylic acid is a micro excavator that penetrates deep to eliminate skin trash like sebum and dead skin cells. That's why you want to upgrade from spot treatment to full face treatments. COSRX BHA Blackhead Power Liquid ($25; dermstore.com) deep cleans pores all over and reduces redness, particularly for those with combination or oily skin.

(Not so) fun fact: While BHAs show visible improvement in pores and acne in as little as two weeks, about 5 percent of people get a purging—an annoying uptick in pimples as the pores empty out before skin actually clears, says Ciraldo. One effective acne product to treat those pimples is Paula's Choice Skin Perfecting 2% BHA Liquid Exfoliant.

BHAs are more than a pimple foe, however. Like AHA, it has peeling properties, just gentler, so it's also good for treating keratosis pilaris—CeraVe SA for Rough & Bumpy Skin is a great drugstore option. This makes BHAs a great option for sensitive skin that needs to treat sun pigmentation or blotchy melasma. Remember that skin will improve and lighten, just not as quickly as a treatment with glycolic acid.

How do you add AHAs and BHAs to your skincare routine?

Now that you're convinced that these hydroxy acids work, it depends on how sensitive your skin is. "All exfoliating products should be integrated into the skincare routine slowly, starting just three times per week and increasing weekly as tolerated," recommends Elyse Love, MD, a board-certified dermatologist in New York City. "Those with sensitive skin will need to take it even slower. Toners are an easy way to add acids to a skincare routine without altering other components of the routine." La Roche-Posay Effacalar Clarifying Solution is a great toner for acne to try. This affordable skincare brand offers a line of products that also includes Vitamin C serums and retinols.

Starting with a mild AHA, like citric acid, is a good idea. We stand by Too Cool For School Caviar Lime Hydra Bubble Toner ($20; toocoolforschool.us)—a citric acid and moisturizing hyaluronic acid blend that comes out as a cloud-light foam yet wipes away the gluey top layer and perks up skin after too much sun.

Creams with AHAs and BHAs are the least irritating of all the options. For dry skin, try a lactic acid cleanser to soften and moisturize skin à la Cleopatra. The coconut oil-based Hanskin Pore Cleansing Balm-AHA ($22; ulta.com) does just that. But if you're looking for higher concentrations of acids, opt for a mask because they are not meant to be used daily, adds Love.

Products with concentration around 10 percent—like Herbivore PRISM 12% AHA + 3% BHA Exfoliating Glow Serum ($54; sephora.com) that offers a medley of naturally occurring lactic, glycolic, and malic acids—reveal smoother, more even skin tone within two to four weeks.

If your skin is usually friendly with new ingredients, look for something with glycolic acid at the top of the ingredient list, like Mad Hippie Exfoliating Serum ($30, ulta.com). Glycolic acid has the smallest molecule of all the AHAs, so it penetrates deep into skin and is most effective at banishing sun spots and fine lines, especially on the cheeks.

To target congested pores and inflammation, use BHAs on the T-zone and the skin around the mouth, suggests Ciraldo. Perricone MD No:Rinse Intensive Pore Minimizing Toner ($44; dermstore.com) lets you zero in on these areas, which is particularly handy on hot, humid days.

You should also consider using AHAs and BHAs separately in shifts, say a cleanser with AHA in the morning and a BHA toner at night. "Combining acids should be left to the experts to prevent irritation," says Love. Instead, consider expertly formulated products that add just the right amount of AHAs and BHAs to keep your skin from flaring up. For instance, Volto Urbano Exfoliating Mud Mask ($60; amazon.com) contains the milder betaine salicylate, along with glycolic and mandelic acids and nourishing plant oils, so you can mask away without worry. Using a face oil in conjunction with AHAs and BHAs can also help improve your skin’s barrier and build up resistance.

However, if you decide to incorporate AHAs and BHAs into your beauty routine, follow the Golden Rule of Acids—thou shalt wear sunscreen daily. Not only do you need sunscreen to make sure you're not undoing your path to dewy skin, AHAs and BHAs cause skin sensitivity to UV light, making you more susceptible to sunburn even 24 hours after application.

You'll also want to talk with your dermatologist if you're planning to have any procedures, including waxing, since the acidic nature can potentially burn the skin, adds Ciraldo. Pregnant women should check with their OB-GYN as research is inconclusive on how AHAs and BHAs affect the fetus.

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  2. Sharad J. Glycolic acid peel therapy - a current review. Clin Cosmet Investig Dermatol. 2013;6:281-288. doi:10.2147/CCID.S34029

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