Everything You Need To Know About AHAs & BHAs

by Miki Hayes
woman using a cotton round on her face
Yulia Shaihudinova/Moment/Getty Images

Whether you're interested in treating acne, signs of aging, or just want a good chemical exfoliator, you may be familiar with skincare products that contain ingredients like salicylic and glycolic acid. But with what can seem like infinite options, what level of AHAs and BHAs should you use on your skin? Turns out, there are a number of factors that can determine which type and concentration of these exfoliators is best for your skin. So to find out some more about how to pick the best acid for your personal needs, I emailed with a couple of experts.

Cindy Kim, co-founder of Silver Mirror Facial Bar, and Rebecca Kazin, MD, of the Washington Institute of Dermatologic Laser Surgery and the Johns Hopkins Department of Dermatology, both let me in on why alpha hydroxy acids and beta hydroxy acids are so important to use in your skincare, and what you should look for when selecting one. According to Kim, "without extra exfoliation, we build up a lot of dead skin, which can cause dullness, flakiness, clogged pores, bumpiness, sagginess, wrinkles, and uneven skin tone." By adding an AHA or BHA to your lineup, you can tackle these issues, improve the texture and tone of your skin, and your other skincare products will even become more effective, she says. What's not to love about that? So you can really tailor your skincare to fit your personal needs, here are nine things to know about incorporating a hydroxy acid into your routine:

1. Use A Product That Won't Wash Off

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Glycolic Acid 10% Moisturizer, $45, Peter Thomas Roth

According to Kim, the best form of AHA or BHA to incorporate into your regimen is a product that won't be washed off such as toners, gels, wipes, serums, and even moisturizers. It's best to apply your hydroxy acid right after cleansing because "AHAs and BHAs need to be absorbed into the skin to work," she says.

2. You'll Build A Tolerance

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Sanitas Skincare Brightening Peel Pads, $74, Silver Mirror Facial Bar

AHAs and BHAs come in a variety of concentrations. And while the higher the percentage means the stronger the product, it's still best to start low and work your way up. If you use a hydroxy acid too frequently or use a concentration that is too high, your skin may become irritated or inflamed, says Kim. If this happens, she recommends cutting back the number of times per week you use the product and/or its strength. Dr. Kazin reminds that generally, "Oily, sebaceous skin will be able to tolerate a higher strength versus dry, sensitive, thin skin.

3. Sunscreen Is A Must

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Tarteguard 30 Sunscreen Lotion Broad Spectrum SPF 30, $32, Tarte Cosmetics

Even though wearing sunscreen on the daily is a good habit to have regardless of the types of products you use, it is essential if you incorporate an acid into your skincare routine. "AHAs make you photosensitive, so wearing sunscreen every day is a must no matter what," says Kim. To help reduce this photosensitivity, try to limit your AHA use to nighttime only.

4. Two Is The Max

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Drunk Elephant T.L.C. Sukari Babyfacial, $80, Sephora

While everybody's hydroxy-acid tolerance may be different, Kim says that using more won't necessarily give you better results. Whether you only use AHAs and BHAs once or twice per week, or once or twice per day, one or two products is all you really need to get the job done. For example, you don't need to use a mask, toner, and serum that all contain acids at the same time— just pick one or two max.

5. AHAs Are Better For Drier Skin Types

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PCA SKIN Smoothing Toner, $34, PCA SKIN

According to Kim, AHAs are "Ideal for drier skin types and those with aging concerns" because they have humectant properties to help hold moisture in the skin. Dr. Kazin adds that glycolics in particular can be more irritating, so sensitive skin-types should look for lower concentrations or opt for lactic or mandelic acids instead. Kim explains that lactic and mandelic acids have larger molecular sizes, making them gentler than glycolic acid. Mandelic acid is especially good for darker skin tones and targeting acne, says Kim, because there is less risk of causing hyperpigmentation, and it has anti-bacterial properties and helps regulate sebum production.

6. BHAs Are Better For Oilier Skin Types

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Dr. Jart+ Dermask Micro Jet Clearing Solution, $9, Sephora

On the other hand, BHAs can actually penetrate pores to clean them out, so are better suited to oily, acne-prone skin with concerns like breakouts, blackheads, and large pores, says Kim. While these don't cause photosensitivy like AHAs, BHAs can cause dryness especially if used too frequently.

7. AHAs Are Most Effective At Concentrations Of 8 To 10 Percent

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The Ordinary Lactic Acid 10% + HA 2%, $7, Deciem

If you're new to AHAs, Kim recommends starting with a concentration lower than 8 percent. However, if you've "built up a tolerance to lower concentrations or have more serious concerns with anti-aging, hyperpigmentation, and roughness," look for an AHA concentration of around 8 to 10 percent, says Kim.

8. BHAs Are Most Effective At Concentrations Of 1 To 2 Percent

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Sunday Riley U.F.O. Ultra-Clarifying Face Oil, $80, Sephora

With concerns such as occasional breakouts, mildly clogged pores, eczema, or rosacea, Kim says 1-percent BHAs are a good starting point. If you have "active acne and breakouts as well as hyperpigmentation" though, she recommends going for a 2-percent salicylic acid instead.

9. The Weather Can Make A Difference

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While your tolerance of hydroxy acids depends on your skin type and history of use, it can also depend on your environment, says Dr. Kazin. For example, normal to oily skin-types can use AHAs and BHAs up to twice per day in oilier areas or if the weather is warm and/or humid. Normal to dry skin-types, on the other hand, "may only be able to use them once a day, every other day, or not at all during cold, dry months," says Dr. Kazin. As amazing as hydroxy acids can be for your complexion, it's important to monitor your skin throughout your use and throughout the year to make sure your skincare routine is perfectly tailored to give your skin everything it needs.

Images: Getty Images (2)