What are beta-hydroxy acids (BHAs)?

In the quest for the perfect zit-zapping ingredient, you have come across beta-hydroxy acids—BHAs, for short. But what are BHAs, and how do they work? Long story short: They gently exfoliate the skin and penetrate deep into pores to dissolve excess oil (food for acne-loving bacteria).

Here we’ll explain BHAs, their benefits, and their potential side effects. And since BHAs are available over the counter, we even have a list of recommended products.

What are BHAs?

Beta-hydroxy acids are a type of chemical exfoliant used in skincare. BHAs are found in many topical skincare products, such as cleansers, toners, moisturizers, scrubs, peels, and masks. They slough away dead skin cells and penetrate deep inside the pores to absorb excess sebum (skin’s natural oil). These products are effective because BHAs are oil-soluble, helping them penetrate into the skin’s deeper layers.¹ 

Salicylic acid is the most commonly used BHA in skincare.² Although BHAs are often used to treat acne, they can also help reduce the appearance of fine lines and wrinkles and improve skin texture.

Types of BHAs

There’s really only one beta-hydroxy acid commonly used in skincare, and that’s salicylic acid. However, citric acid is sometimes used as a BHA as well. Here’s our breakdown: 

• Salicylic acid is used to treat acne, redness, and inflammation. It’s also found in anti-aging formulas. This ingredient may be listed as salicylic acid, salicylate, sodium salicylate, or willow extract (although willow extract differs slightly).³

• Willow bark extract is derived from willow trees. It’s a natural source of salicin, a gentler relative of synthetic salicylic acid. Willow bark extract shares many of salicylic acid’s primary benefits.⁴ Its anti-inflammatory and comedolytic properties can help treat acne.⁵

• Citric acid has a unique chemical structure where it can be considered both an alpha-hydroxy acid (AHA) as well as a BHA. In particular, citric acid has been found to increase the skin renewal rate and increase the thickness of the top layer of our skin.⁶   

Get ready for a plot twist: Technically speaking, even salicylic acid isn’t a true beta-hydroxy acid—its chemical structure is slightly different.⁷ However, it’s been classified for years as a BHA and is generally considered to be one—even by Food and Drug Administration standards.⁸ Both salicylic acid and BHAs are oil soluble, making them efficient at removing excess oil.

What is BHA used for?

As we’ve already covered, BHAs treat acne and signs of aging. BHAs are oil-soluble, so they penetrate deeper to unclog pores by dissolving excess sebum. This sets them apart from AHAs (glycolic acid, lactic acid) and other ingredients like azelaic acid. BHAs treat acne and help prevent breakouts, reduce excess oil, smooth skin texture, and reduce the appearance of enlarged pores. 

• BHAs exfoliate the skin. BHAs are gentle chemical exfoliators. In particular, the keratolytic effect of salicylic acid “peels” skin by softening and removing dead skin cells.⁹

• BHAs unclog pores. The same exfoliating properties of BHAs also help unclog pores. BHAs—specifically salicylic acid—can also decrease the number of pustules and inflammation associated with acne.¹⁰

• BHAs dissolve excess sebum. BHAs are well suited for acne-prone skin and oily skin types. Their oil-soluble properties let them penetrate deeper into the skin layers and dissolve excess sebum.

How to use BHAs properly

BHAs are generally safe for daily use, but they may need some getting used to first. As with any exfoliant, you’ll need to wear sunscreen with at least SPF 30 during the day to protect your skin from sun damage (as you should already be doing anyway!).

How you use BHAs will depend on which product they’re in, but here are some guidelines to ease BHAs into your skincare routine: 

• Begin with a concentration of 0.5% to 5%—consistent with most OTC beta-hydroxy acid products.

• Use once or twice weekly for a few weeks or until your skin adjusts. Increase frequency gradually as tolerated. 

• Always apply your treatment to a clean face and follow up by applying a moisturizing cream or lotion designed for acne-prone skin. 

Most importantly, don’t be shy! Reach out to your dermatologist or dermatology provider with any questions. They’re a great resource when starting a new skincare routine or product.

Possible BHA side effects

So, why the adjustment period? Like many exfoliants, BHAs can have side effects. In most cases, they’re manageable and tend to go away on their own, but certain skin types may experience more noticeable drawbacks. Easing into BHAs is the safest method.

Common side effects of BHAs may include: 

• Dryness

• Redness

• Flaking 

• Irritation

If you experience worsening symptoms or side effects that don't go away after you stop using BHAs, seek medical advice from your dermatologist or healthcare provider.  

In addition, those who have an allergy to salicylic acid, aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), or salicylates should not use salicylic acid. If you have any questions or concerns about this, we recommend discussing it with your allergist or other local healthcare providers.

Product recommendations for the face

Countless OTC products contain BHAs. But with so many options, the choice can be daunting. We asked our experts and wrote up a fully vetted list of products we’d recommend to our family and friends: 

• Stridex Wipes quickly clean, treat and prevent acne. They contain a 2% salicylic acid solution that works great in a pinch. Look for the wipes in the red box. 

• Neutrogena Oil-Free Acne Wash with salicylic acid helps treat and prevent breakouts. This oil-free formula gently cleanses and exfoliates to get rid of acne. It’s gentle enough to use daily without drying or irritating your skin.  

• Paula's Choice 2% BHA Liquid Exfoliant is a leave-on exfoliant that unclogs pores, smooths wrinkles, and brightens skin tone. It can be used up to twice daily.

• Paula's Choice RESIST Advanced Pore-Refining Treatment 4% BHA is the big sister to Paula’s 2% BHA formula. This treatment is infused with antioxidants to visibly reverse the signs of aging. It works twice as hard to minimize pores, bumps, and skin texture, so you might notice results faster.

Product recommendations for the body

When it comes to treating the body, we’re a little biased—the acne body wash by Curology is our go-to favorite. But we would be remiss not to include Neutrogena’s Body Clear Body Wash. Both are excellent choices, so it all comes down to your personal preference.  

• Curology acne body wash was formulated by dermatologists to be tough on body acne but gentle enough to use every day. It’s a light, foaming body cleanser with 2% salicylic acid to target breakouts and stop them at the source. The acne body wash is non-comedogenic and hypoallergenic, with no added fragrances, dyes, or parabens.    

• Neutrogena Body Clear Body Wash is an alternative designed for acne-prone skin. This oil-free body wash fights breakouts using 2% salicylic acid to exfoliate and clear out clogged pores. It’s a heavy lifter that’s still gentle enough to use every day.

Caring for your skin with Curology

Curology helps take the guesswork out of your skincare routine. Our in-house licensed dermatology providers work with you to examine your unique skin, assess your skin goals, and provide custom treatment options. We create custom treatment plans, prescribe personalized products, and give the advice to help keep your skin looking and feeling its healthiest. 

Getting started is simple: Just answer some questions and upload a few selfies to help us get to know your skin. If Curology is right for you, we’ll pair you with one of our licensed dermatology providers who will create a personalized prescription formula for your top skin concerns. They’ll also offer additional products to help you reach your skin goals.* As your skin naturally changes, we’re always here to answer questions and tweak your prescription formula if necessary. 

P.S. We did the homework so you don’t have to:

1. Sarkar, R, et al. Comparative Study of 35% Glycolic Acid, 20% Salicylic-10% Mandelic Acid, and Phytic Acid Combination Peels in the Treatment of Active Acne and Postacne Pigmentation. J Cutan Aesthet Surg. (July-September 2019).

2. U.S. Food and Drug Administration. Beta-hydroxy acids. (2022 February 25).

3. U.S. Food and Drug Administration. Beta-hydroxy acids. Ibid.

4. Desborough, MJR, et al. The aspirin story – from willow to wonder drug. Br J Haematol. (2017 May 24).

5. Arsenie, LV, et al. Azelaic acid-willow bark extract-panthenol – Loaded lipid nanocarriers improve the hydration effect and antioxidant action of cosmetic formulations. Industrial Crops and Products, Volume 154. (2020).

6. Tang, SC, Yang, JH. Dual Effects of Alpha-Hydroxy Acids on the Skin. Molecules. (2018 April 10).

7. Kornhauser, A, et al. Application of hydroxy acids: Classification, mechanisms, and photoactivity. Clinical, Cosmetic, and Investigational Dermatology. (2010).

8. U.S. Food and Drug Administration. Beta-hydroxy acids. Ibid.

9. Kornhauser, A., et al. Application of hydroxy acids: Classification, mechanisms, and photoactivity. Clinical, Cosmetic, and Investigational Dermatology. Ibid.

10. Zheng, Y, et al. Clinical evidence on efficacy and safety of an antioxidant optimized 1.5% salicylic acid (SA) cream in the treatment of facial acne: An open, baseline-controlled clinical study.Skin Research and Technology. (2013 January 19).

Laura Phelan is a board-certified Family Nurse Practitioner at Curology. She earned her Masters of Science in Nursing at Benedictine University and went on to get her post-master’s certificate as a Family Nurse Practitioner at the University of Cincinnati.

* Subject to consultation. Subscription is required. Results may vary. 

Written by

Curology Team

Medically reviewed by

Laura Phelan, NP-C