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Alpha Hydroxy Acids vs. Beta Hydroxy Acids: How to Choose a Chemical Exfoliant for Your Skin Type

Find out how to incorporate alpha and beta hydroxy acids into your skin-care routine.
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Facial exfoliation is a critical part of any skincare routine as it can help even and smooth out your skin tone while brightening your complexion. That said, it's also one of the trickiest steps to decode. It can be tough to navigate how often to exfoliate, when to exfoliate during your routine, and how strong of an exfoliant to use.

To make matters even more complicated, you have two types of exfoliation to choose from. The first is physical aka mechanical exfoliation, which involves using a tool or scrub to physically buff away dead surface skin cells. The second is chemical exfoliation, which calls on an acid ingredient to gently dissolve dead skin cells. There are three main types of ingredients that are used in chemical exfoliation, known alpha hydroxy acids (AHAs), beta hydroxy acids (BHAs), and (less common but still popular) poly-hydroxy acids (PHAs). While the acids function similarly, you may want to choose one over the other depending on your skin type and concerns. 

If you're hoping to get the most from chemical exfoliation, learning the differences between AHAs and BHAs is worth the effort. Ahead, learn more about AHAs and BHAs, including which one is better for you and how to incorporate it into your routine.

What's the Difference Between Alpha Hydroxy Acids and Beta Hydroxy Acids?

"Alpha hydroxy acids are a group of acids that typically are found in fruits, sugar cane, and milk that are commonly used in skincare products," explains Sumayah Jamal M.D., Ph.D., a board-certified dermatologist at Schweiger Dermatology Group in New York. Some common examples of alpha hydroxy acids include lactic acid, glycolic acid, citric acid, and mandelic acid.

"They primarily are used to exfoliate, but they also help improve the appearance of fine lines and wrinkles, even out and brighten skin tone, and stimulate collagen," adds Karen Hammerman M.D., a board-certified dermatologist at Schweiger Dermatology Group in Garden City, New York. (Related: Exfoliating Gloves Are the TikTok Trend That'll Give You Baby-Soft Skin)

Beta hydroxy acids work similarly to alpha hydroxy acids, but the biggest difference is how they penetrate your skin. "Unlike alpha hydroxy acids that are water-soluble and derived from plants, beta hydroxy acids are oil-soluble," explains Kim Nichols, M.D., a board-certified dermatologist based in Connecticut. That means they can cut through oil in your pores. "Typically, they can get deeper into pores than AHAs do to remove excess sebum and clear out congestion in the follicles," says Dr. Nichols. Due to their ability to penetrate deeper into the skin and unclog pores, beta hydroxy acids are typically recommended to help reduce acne. Salicylic acid, which comes from willow bark, is the most common form of beta hydroxy acids.

What Skin Types Should Use Alpha Hydroxy Acids?

"AHAs are primarily used for mild hyperpigmentation like age spots, melasma, scars, enlarged pores, fine lines, and uneven skin tone," says Macrene Alexiades M.D., a New York-based board-certified dermatologist. Mature and darker skin types often benefit from incorporating an alpha hydroxy acid into their routine due to their ability to help signs of aging and even skin tone, since darker skin tones are more prone to pigmentation, says Dr. Nichols.

"When you use an ingredient such as alpha hydroxy acids, they work to reveal that underlying layer of healthy skin. Eventually, they reveal a more vibrant and youthful glow," says Dr. Nichols. "AHAs can also increase the thickness of deeper layers of skin and restore that firmness." (Related: The Best Body Exfoliators for Smooth Skin, According to Customer Reviews)

Generally speaking, most alpha hydroxy acids are irritating for sensitive skin types. That said, some types of AHAs are more gentle than others. "Lactic acid is the most hydrating of the AHAs, so it can be used for sensitive skin and dry skin," says Dr. Hammerman. As a rule of thumb, don't use any formulas with concentrations higher than 15 percent, advises the Cleveland Clinic.

What Skin Types Should Use Beta Hydroxy Acids?

"BHAs are excellent for oily and acne-prone skin types," says Dr. Jamal. Beta hydroxy acids (salicylic acid being the most common) have antibacterial properties making them helpful for those who struggle with acne. Additionally, low concentrations of BHAs (e.g. two percent salicylic acid) can help reduce inflammation making them suitable for sensitive skin types as well, adds Dr. Nichols.

How to Incorporate AHAs or BHAs in Your Routine:

When implementing new products into your routine, it's always best to do a patch test before committing to the whole thing, especially when it comes to acids. "Like any new skin-care [ingredient] being integrated into a routine, AHAs and BHAs can cause irritation and redness if used improperly," says Dr. Nichols. "I recommend integrating an AHA or BHA into a skin-care regimen gradually to avoid aggravating the skin."

Try applying the product with AHAs or BHAs on a small, inconspicuous area (think: jawline) before applying it to your whole face to see if you experience any reactions, says Dr. Hammerman. If you don't notice any issues, you can start by exfoliating once a week and increase frequency as tolerated. Typically, oily and acne-prone skin types can get away with exfoliating more often or using a higher concentration than dry and sensitive skin types.

For instance, acne-prone skin types can use a salicylic acid cleanser daily to help with breakouts, says Dr. Jamal. You can try Skinfix Acne Azelaic Acid BHA/AHA Cleanser (Buy It, $35, sephora.com) which infuses salicylic acid, azelaic acid, and niacinamide to address all types of acne without stripping or drying out your skin. (Related: This $8 Exfoliating Washcloth Removes Dead Skin Like No Other)

Both AHAs and BHAs are incorporated in a wide range of skin-care products from moisturizers, cleansers, and sunscreens to toners. For instance, Tatcha Texture Tonic (Buy It, $60, sephora.com) contains apple, grapefruit, orange, lemon, lime extracts, niacinamide, and Japanese mugwort to gently exfoliate the skin and unveil a brighter, more even skin tone. Whichever type of product and acid you end up choosing, make sure you follow up with sunscreen in the mornings as chemical acids can increase sensitivity to the sun.

Like all things in skin-care, it may take some trial and error to figure out what works best for you. Once you've found what works for your skin type, though, the results will likely be worth the wait. If you're unsure what to add to your routine or need a little more guidance, consult with your dermatologist for product recommendations that work for you.