AHAs Or BHAs: Do You Know The Difference Between These Skin Care Acids?
In the world of exfoliation, there are a lot of variables. First up: Do you want a physical exfoliator, which consists of granular particles to manually scrub the skin? Or do you want a chemical exfoliator, which lifts off dead skin cells by breaking apart the bonds between cells or accelerating turnover? If you decide to go the latter route, then that poses the question of what kind of chemical exfoliator you want. There are several to choose from, like fruit enzymes, retinols, dicarboxylic acids, poly-hydroxy acids, alpha-hydroxy acids, and beta-hydroxy acids.
The last two on the list are arguably the most common, but how much do you know about AHAs and BHAs—or which type is better suited for what skin type? Here, we provide all you need to know to make an informed choice.
What are AHAs?
Alpha-hydroxy acids are plant-derived compounds that are hydrophilic, meaning they are water-loving. Like other exfoliants, they are used to slough off dead skin cells, brighten, even tone, and reverse signs of aging. But because of their hydrophilic qualities, they are also moisturizing as well—which sets them apart from other chemical exfoliants. "They can be simultaneously exfoliating and hydrating, making them very beneficial to many skin types," says board-certified dermatologist Mona Gohara, M.D.
Of the AHAs, lactic acid and glycolic acid are often considered some of the most beneficial, as they've both been shown to1 increase skin cell turnover, improve moisture content of skin, and reduce the appearance of fine lines. They are also the most studied and researched, which is why you'll find them in more skin care products. However, there are other forms, like malic and citric acids.
What are BHAs?
Beta-hydroxy acids2 are chemicals that are lipophilic, meaning it's oil- and fat-loving. "These are really good at breaking through oil and sebaceous skin," says Gohara. "These are both beneficial, but they have different roles."
Salicylic acid is a BHA, which is particularly beneficial for acne-prone skin3 due to its ability to unclog pores. "It is able to penetrate the skin deeper into pores to help remove dead skin cells, fight bacteria, and control excess sebum," says board-certified dermatologist Zenovia Gabriel, M.D. As she notes, salicylic acid is also found to be antibacterial, making it particularly effective for acne-prone individuals, as it not only dissolves excess oil, but it targets the acne-causing bacteria building up in the pores. These exfoliating acids are also great at smoothing out the rough, bumpy skin associated with keratosis pilaris.
How to decide how to use either.
Given what we've learned about the various benefits of these two types of chemical exfoliants, you might deduce there are more appropriate skin types and uses for either.
Now, since these acids will be formulated with other ingredients, there'll be some nuance to each and every product you try. For example, if an acid is buffered with calming ingredients like hyaluronic acid or squalane, it might not be as irritating to those with sensitive skin—even if it's a "harsher" acid. And on the flip side, a more gentle, hydrating acid may be formulated at a higher concentration and bolstered with other powerful actives, making it stronger.
Regardless, here are some general guidelines:
- Easily irritated skin should use AHAs, specifically lactic acid. As AHAs are water-loving, and therefore mildly hydrating, this will provide more moisture to sensitive skin. Plus, lactic acid specifically is a larger molecule (as far as molecules go), so it stays atop the epidermis so it is a far more gentle exfoliation. The smaller the molecule, the deeper it can penetrate—therefore making the effects stronger.
- If you are seeking younger-looking skin, stick to glycolic acids (AHAs). As glycolic acids have been shown to increase collagen production4, they will help your skin look firmer and more taut. They also help fade dark spots and even tone.
- Oily and acne-prone skin should use BHAs. Because BHAs can dissolve oil, they are perfect for those with excess sebum and clogged pores. Not only that, but because of their bacteria-neutralizing powers, they can target the bacteria buildup that causes breakouts.
- The same person can use both; just use them on different days. "Don't use them at the same time," notes Gohara—if nothing else, it will just be too harsh for the skin to use that many exfoliating ingredients. "But if someone wants to use a more gentle AHA every day but then use a BHA when they're breaking out, they certainly can do that."
A well-formulated chemical exfoliator can be a magical thing for your skin: It can slough away dead skin cells, encourage turnover, promote collagen, increase brightness, reduce acne, and so on. However, there are plenty to choose from, and each has its own strengths and weaknesses. If you are curious about two of the most famous, AHAs and BHAs, here's the most basic take-away: AHAs will be more beneficial for sensitive and dry skin; BHAs are better for acne-prone and oily skin.
Alexandra Engler is the beauty director at mindbodygreen and host of the beauty podcast Clean Beauty School. Previously, she's held beauty roles at Harper's Bazaar, Marie Claire, SELF, and Cosmopolitan; her byline has appeared in Esquire, Sports Illustrated, and Allure.com. In her current role, she covers all the latest trends in the clean and natural beauty space, as well as lifestyle topics, such as travel. She received her journalism degree from Marquette University, graduating first in the department. She lives in Brooklyn, New York.