Alpha Hydroxy Acids vs Beta Hydroxy Acids: What’s the Difference?

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Facial exfoliation is an essential part of any skincare routine because it can help even out and smooth your skin tone while brightening your complexion. That said, it’s also one of the trickiest steps to decode. It can be difficult to determine how often to exfoliate, when to exfoliate during your routine, and what strength of exfoliator to use.

To make things even more complicated, there are two types of exfoliation to choose from. The first is physical, i.e. mechanical, exfoliation, which involves using a tool or scrub to physically remove dead skin cells. The second is chemical exfoliation, which uses an acidic ingredient to gently dissolve dead skin cells. There are three main types of ingredients used in chemical exfoliation, known alpha hydroxy acids (AHAs), beta hydroxy acids (BHAs), and poly hydroxy acids (PHAs) (less common but still popular). Although the acids work the same way, you can choose one over the other depending on your skin type and concerns.

If you’re hoping to get the most out of chemical exfoliation, learning the differences between AHAs and BHAs is well worth it. Ahead, learn more about AHAs and BHAs, including which one is best for you and how to incorporate it into your routine.

What is the difference between alpha hydroxy acids and beta hydroxy acids?

“Alpha hydroxy acids are a group of acids commonly found in fruits, sugar cane, and milk that are commonly used in skin care products,” says Sumayah Jamal MD, Ph. D., a board-certified dermatologist at the Schweiger Dermatology Group in New York. Some common examples of alpha hydroxy acids include lactic acid, glycolic acid, citric acid, and mandelic acid.

Beta hydroxy acids work similarly to alpha hydroxy acids, but the biggest difference is in how they enter your skin. “Unlike alpha hydroxy acids which are water soluble and derived from plants, beta hydroxy acids are oil soluble,” says Connecticut-based board-certified dermatologist Kim Nichols, MD. This means they can cut the oil in your pores. “Typically, they can penetrate deeper into the pores than AHAs to remove excess oil and eliminate congestion in the follicles,” says Dr. Nichols. Due to their ability to penetrate deeper into the skin and unclog pores, beta hydroxy acids are generally 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, large pores, fine lines, and uneven skin tone,” says Macrene Alexiades MD, a board-certified dermatologist based in New York City. Mature and darker skin tones often benefit from incorporating an alpha hydroxy acid into their routine due to its ability to help signs of aging and even skin tone, as darker skin tones are more prone to pigmentation, explains Dr. Nichols.

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

Generally speaking, most alpha hydroxy acids are irritating to sensitive skin. That said, some types of AHAs are milder 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 general rule, don’t use any formula with concentrations higher than 15 percent, advises the Cleveland Clinic.

Which Skin Types Should Use Beta Hydroxy Acids?

“BHAs are great for oily and acne-prone skin,” says Dr. Jamal. Beta hydroxy acids (salicylic acid being the most common) have antibacterial properties, which makes them useful for those struggling with acne. Plus, low concentrations of BHA (for example, two percent salicylic acid) can help reduce inflammation, which also makes them suitable for sensitive skin, adds Dr. Nichols.

How to incorporate AHAs or BHAs into your routine:

When implementing new products into your routine, it’s always best to do a patch test before committing to anything, especially when it comes to acids. “Like any new skincare [ingredient] being incorporated into a routine, AHAs and BHAs can cause irritation and redness if not used correctly,” says Dr. Nichols. “I recommend gradually incorporating an AHA or BHA into a skin care regimen to avoid aggravating the skin.

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

AHAs and BHAs are incorporated into a wide range of skin care products, from moisturizers, cleansers and sunscreens to toners. For example, Tatcha Texture Tonic (Buy It, $60, contains extracts of apple, grapefruit, orange, lemon, lime, niacinamide, and Japanese mugwort to gently exfoliate the skin. and reveal a brighter, more even complexion. Whichever type of product and acid you choose, be sure to apply sunscreen in the morning, as chemical acids can increase sun sensitivity.

As with all things skincare, it may take some trial and error to figure out what works best for you. Once you find what works for your skin type, the results are probably worth the wait. If you’re not sure what to add to your routine or need a little more guidance, consult your dermatologist for product recommendations that are right for you.

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