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AHAs, BHAs, and More: Everything You Need to Know About Exfoliating Acids

The word “acid” has a negative—even scary—connotation, which may prevent some people from diving into acid-based skincare products. Here’s the thing, though: By avoiding acids, you skip some of the most effective and transformative skincare ingredients on the market. Acids are multi-beneficial; not only do they exfoliate by sloughing away dead skin and pore-clogging debris, but they also encourage cellular turnover, boost collagen production, and provide substantial brightening effects. Acids even allow other skincare products to penetrate deeper into the skin, working harder and faster than they would otherwise. Acids, no matter how daunting they sound, are safe, effective, and yes a little misunderstood. It’s time to clear that up.

In skincare, acids can be separated into two categories: AHAs and BHAs, which stand for alpha hydroxy acids and beta hydroxy acids, respectively (the names refer to their chemical makeup). According to master facialist Sarah Akram, each category of exfoliating acid has its own distinct purpose. AHAs, which are typically found in fruits, milk, and sugarcane, “exfoliate the skin’s surface, which is beneficial if you have dry or sun-damaged skin,” she says. “They dissolve dead skin cells and debris from the skin’s surface.” BHAs, on the other hand, are typically found in willow bark and citrus fruits. According to Akram, these “have anti-inflammatory and antibacterial properties, so if you’re prone to breakouts and blackheads, these are perfect to use as they can get deeper into the pores than AHAs.” For BHAs, think pores. For AHAs, think dead surface cells. 


Let’s talk AHAs first, shall we? According to Kerry Benjamin, esthetician and StackedSkincare founder, AHAs “are the main ingredients of most peels and are naturally occurring acids most commonly found in foods.” Depending on the specific acid that’s used, AHAs can treat everything from wrinkles to hyperpigmentation to acne.

Glycolic Acid

It’s derived from fruit and sugarcane and included in skincare products to treat and reverse apparent signs of aging. Benjamin says it’s “great for treating fine lines and wrinkles and sun damage.” It’s also a go-to ingredient for improving skin texture and skin brightening. As such, it’s common to see it in preventative- and anti-aging products. You’ll find it, along with lactic acid, in Weekend Glow Daily Brightening Solution, Doctor's Visit Instant Resurfacing Mask, and The Shortcut Overnight Facial.

Lactic Acid

Naturally, it’s derived from milk (and it can be lab-created) for the purpose of treating “pigmentation, dry, or dehydrated skin, sensitive skin, and even eczema and rosacea due to its natural moisturizing effect on the skin,” Benjamin explains. Yes, even acids can be humectants, which draw moisture into the skin. Lactic acid as one of the most gentle, non-irritating AHAs. If you have sensitive skin, this one’s for you.

Citric Acid

Citric acid likely—and correctly—calls lemons, oranges, and grapefruit to mind; it’s present in all of those citrus fruits. When it comes to skincare, however, Benjamin says citric acid is derived from corn or sugar beets. It’s mainly used to treat acne, sun damage, and superficial pigmentation issues. It can also be used as a natural preservative in skincare products. 

Mandelic Acid

Here’s where we start getting into the nitty-gritty of lesser-known exfoliating AHAs. Mandelic acid, although less common than glycolic, lactic, and citric, is just as effective, especially for people who struggle with acne, thanks to its antibacterial qualities. Benjamin names the almond-derived acid a “great first-time chemical peel” since it doesn’t penetrate as far into the skin as others (like glycolic). Because it takes longer to penetrate the skin, there’s less of a chance that it will irritate sensitive skin.

Azelaic Acid

This one’s also particularly beneficial for those who struggle with acne and rosacea. It’s derived from rye, wheat, and barley, yet according to Akram, it’s actually gluten-free, making it suitable for those with celiac disease. It works by “decreasing swelling and redness,” while “killing the bacteria that infect pores.”

Kojic Acid

It’s derived from mushrooms and other fungi and works to brighten, even skin tone, and reduce the look of fine lines through boosting collagen and elastin production. (Collagen and elastin are naturally present in our skin. They give it plumpness and that bounce-back effect.)


Now onto BHAs. Beta hydroxy acids are best for treating acne because they are anti-inflammatory and antibacterial, and most importantly, work at the pore-level (which is where breakouts form).

Salicylic Acid

The most common BHA is salicylic acid, which is derived from willow tree bark. Benjamin loves this one because it deeply penetrates oil glands, making it ideal for acne-prone and oily skin. It actually dissolves excess sebum and other pore-clogging material, which keeps skin clear and bright. As such, you’re likely to see this ingredient in acne-fighting products, like our Nix It Complexion Solution, Keep the Peace Acne-Calming Cream Cleanser, and Back-Up Plan Acne-Control Body Mist. 

It’s important to note that acids can be combined to simultaneously treat various skin concerns. When combining acids, Akram says, “The main benefit is that you’re getting the best of both worlds that treat different and recurring skin issues.” Benjamin agrees. “Multi-acid peels are one of the safest and most effective ways to gently exfoliate and treat your skin,” she says. “Each acid has its own unique benefits. Combining multiple acids in one peel results in a one-stop shop for everything from acne, dark spots, dryness, redness, and even skin sensitivities like eczema and rosacea.” 

To learn more about common ingredients found in skincare, check out our glossary.