AHAs vs. BHAs: The Key Differences, According to Derms

Radiant, bump-free, and nearly pore-less skin. If this is what your glass skin goals sound like, you need make sure you're using a chemical exfoliant. Alpha-hydroxy acids (AHAs) and beta-hydroxy acids (BHAs) are the pillars of an effective exfoliation routine, so if you haven't heard about them it's about time you learn. Gritty face scrubs of the past, begone!

AHAs and BHAs are chemical exfoliants, meaning you don't need to physically rub sand paper-like formulas on your face to reveal brighter skin. Instead, AHAs and BHAs gently but effectively slough away at dead skin cells and deep clean your pores to reveal a spotless, radiant complexion. Don't get it wrong though—AHAs and BHAs are two completely different groups of exfoliants.

Salicylic acid? BHA. Glycolic acid? AHA. Hyaluronic acid? Neither. Lactic acid? Also AHA. It can be tricky to figure out which ingredient falls under each umbrella, and even harder to understand which does what and what they're each good for. So, we tapped two board-certified dermatologists to break down everything there is to know about each so you can best equip yourself and reach your ultimate #skingoals. Use this easy-to-follow guide to figure out the differences between AHA and BHA and how to choose the right option for your skin.

What Are AHAs?

AHA stands for alpha-hydroxy acid. "AHAs are derived from sugar cane or other plant sources, which is why they are often referred to as fruit acids," says Howe. Among AHAs is glycolic acid, which, according to Howe, is the smallest of the AHAs, is derived from sugar cane, and is the most widely used type in skincare products. Other popular AHAs are lactic, citric, and malic acids. Markowitz notes that AHAs are generally recommended for normal to dry, sun-damaged skin thanks to their ability to enhance natural moisturizing factors within the skin.

The Benefits of AHAs

• They target all areas of the skin: "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."
• Stimulate collagen production: AHA's stimulate collagen production, making them ideal for those looking to reduce the appearance of fine lines. "[They] 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," Howe says. Markowitz agrees, adding that AHAs have been proven effective in reducing visible signs of sun damage and wrinkles (FYI: AHAs don't replace sunscreen).

What Are BHAs?

BHA—which stands for beta-hydroxy acid—is a topical chemical exfoliant that works to balance oily skin and clear breakouts. That ever-popular acne-busting ingredient, salicylic acid? Yep, it's a BHA. "BHAs are organic carboxylic acids that work on the skin’s surface and deep inside the pore," explains Markowitz. "They are oil-soluble, so it’s most often preferred for balanced to oily skin prone to bumps, clogs, blemishes, and enlarged pores." Howe notes that while BHAs are structurally similar to AHAs, they differ "in their position of the one hydroxyl group."

The Benefits of BHAs

• Ideal for sensitive skin: Users of BHAs will reap the skin-calming properties of the acid—it gets bonus points for being gentle enough for sensitive skin types, including those prone to redness or rosacea. This rings true with the most familiar type of BHA, salicylic acid, too. "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."
• Penetrate deeply: Howe says that 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," he notes. "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."
  

AHA vs. BHA: How to Choose

In general, if you are looking for anti-aging benefits, have dry skin, or just want to target the top layer of your skin (such as when treating hyperpigmentation), you'll probably want to opt for an AHA. If you're looking to penetrate deeper to treat cystic acne, or if you have sensitive skin, a BHA will be a better bet.

Markowitz explains that AHAs and BHAs, and their strengths, depend on the mode and formula. "For example, an in-office peel could have a substantial impact on the skin with associated downtime, while an over-the-counter cream containing these ingredients will give a more limited effect that takes time to accomplish the desired result," she says.

You don't necessarily have to pick one or the other. As mentioned above, many skincare products combine both AHAs and BHAs. It's about finding a formula with the right percentages of each for your skin type and goals.

Combining AHAs and BHAs

Many products make use of both AHAs and BHAs, and though they can cause skin irritation if doses are too high, Markowitz recommends looking for a moisturizer that already has a combination of AHA and BHA for a balanced formula. For the face, we recommend SkinMedica's AHA/BHA Cream ($48). For the body, we love Skinfix's AHA/BHA Renewing Cream ($48). Bottom line: If your skin requires a little more TLC (think stubborn pores, deep-set wrinkles, or rough bumps), you could do well with a combo.