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AHA vs. BHA: What's the Difference, and Why Should You Use Them?

If you want healthy-looking skin, there are two forms of acid you have to familiarize yourself with: AHAs (alpha-hydroxy acids) and BHAs (beta-hydroxy acids). Neither acid is better than the other necessarily; they just target different needs. Plus, there are so many products that combine both ingredients that you can just tackle all those skin concerns at once—but we'll get to that later. 

That said, despite the plethora of products we try on a monthly basis with both AHAs and BHAs, we're still far from experts on the subject, and to be honest, if hard-pressed, we'd have trouble explaining exactly what the acids are, how they differ, and exactly what their glow-worthy benefits are. So we thought we'd leave that to an expert in addition to leaving you with a pre-approved shopping list of our favorite AHA/BHA skincare goodies. Ahead, Kenneth Howe, MD, a dermatologist at Wexler Dermatology, breaks it down for us. Your healthier, glowing skin awaits! 

Michela Buttignol/Byrdie

What Are AHAs?

AHA stands for alpha-hydoxy acids. "AHAs are derived from sugar cane or other plant sources, which is why they are often referred to as fruit acids," says Howe. He says that glycolic acid, which is the smallest of the AHAs and is derived from sugar cane, is the most widely used AHA in skincare products. 

AHA Benefits

"AHAs exert benefits both to the outer layer of the skin (epidermis) and the deep layer (the dermis)," says Howe. "In the epidermis, AHAs have an exfoliative effect, increasing the shedding of dead skin cells retained at the surface. They do this by gently cleaving the retained bonds between dead skin cells. Once cut loose, those cells can then fall off, or exfoliate."

AHAs also help stimulate collage production, which is why it is so important when wanting to reduce the appearance of fine lines. "AHAs do this both by increasing collagen synthesis by fibroblasts (the collagen-producing cells in the skin), and by decreasing degradation of the existing dermal matrix," he says. 

What are BHAs?

BHA stands for beta-hydroxy acids. "They are organic carboxylic acids with one hydroxyl group attached to the beta position of the carboxyl group. So they differ from alpha-hydroxy acids in the position of the one hydroxyl group—but otherwise, they’re quite similar in structure," says Howe. The most common BHA that everyone fighting acne is very familiar with is salicylic acid. 

BHA Benefits

"Salicylic acid (SA) is fat-soluble, so it’s good on oily skin and gives it an enhanced ability to penetrate pores," says Howe. "These features explain why SA is used in a lot of OTC acne products."

He also says the salicylic acid is known to fight bacteria and can be used to treat calluses and other areas of dry skin. "In the highest concentrations, it is used to treat warts. It exerts this effect in a similar way to what AHAs do—by ungluing dead skin cells from each other—but salicylic acid penetrates deeply," he says. 

When Do You Use AHA vs. BHA?

When choosing between AHA and BHA, it comes down to the way in which you want the products to work. If your issues are deeper, like cystic acne or just bad acne in general, you'll want to use either BHA or an AHA/BHA combination. It will penetrate and get to the root of the problem. For this reason, everyday use of BHAs is totally acceptable.

For an issue like dry skin, however, you should focus on an AHA. An AHA/BHA combo might work depending on your skin type, but when your goal is to exfoliate just the top layer of your skin you should be using an AHA. Unlike BHAs, though, AHA shouldn't be used every day for fear of skin damage—instead, you should use it every other day, at maximum. Use either AHA or BHA right after cleansing and toning in your nightly routine, unless you're instructed otherwise.

SkinCeuticals C + AHA $136

"It blends two AHAs (glycolic and lactic acids) with vitamin C and hyaluronic acid (HA). The HA soothes the skin, making the AHAs more tolerable, while vitamin C provides antioxidant activity," says Howe. 

T.L.C. Framboos(TM) Glycolic Night Serum 1.69 oz/ 50 mL
Drunk Elephant T.L.C. Framboos Glycolic Night Serum $90

We swear by this serum. Made with a 12% combination of AHA and BHA, it gives you smoother and clearer skin in just days. 

Good Genes Treatment
Sunday Riley Good Genes All-In-One Lactic Acid Treatment $158

This treat from Sunday Riley is made with a really potent lactic acid that exfoliates away any dead skin cells to reveal smooth, brighter-looking skin. 

SkinMedica AHA/BHA Cream $44

"My favorite BHA is actually a combination AHA/BHA: It's SkinMedica’s AHA/BHA cream. It's nicely balanced, well tolerated, and exfoliates the skin to an even glow," says Howe. 

2% BHA Liquid Exfoliant
Paula's Choice Skin Perfecting 2% BHA Liquid Exfoliant $30

This leave-on formula uses BHA to shed away any dead skin cells and tighten up enlarged pores. It's super lightweight and quickly absorbs into the skin. You can easily use it twice a day. 

Herbivore Blue Tansy AHA + BHA Resurfacing Clarity Mask $48

Whenever we break out, we immediately use this mask. It's made with willow bark, which is a natural BHA that is high in salicylic acid, to treat any blemishes and prevent future breakouts. 

CosRx BHA Blackhead Power Liquid $22

For blackhead problems, we like to apply this BHA-infused liquid after we tone. It gets rid of excess sebum to reduce the production of those nasty blackheads and unclog pores.

Need to fight post-acne pigmentation? The addition of willow bark water will help brighten your complexion while the BHA fights persistent blemishes.

Alpha Beta(R) Universal Daily Peel 60 Treatments
Dr. Dennis Gross Alpha Beta Universal Daily Peel $88

When it comes to AHA products, this peel from Dr. Dennis Gross is basically the holy grail. It does everything from clearing pores to stimulating collagen production and reducing the appearance of fine lines, all in an easy, two-step peel process.

This post was originally published at an earlier date and has since been updated.

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