A Skincare Guide to Beta Hydroxy Acid or BHA

An introduction to beta hydroxy acid (BHA), its benefits, side effects, and best products

When people refer to BHA or beta hydroxy acid, they are usually referring to salicylic acid, a common and effective topical treatment for acne or dandruff. But there are is more to BHAs or beta hydroxy acids than just salicylic acid or acne. So what exactly is BHA, or beta hydroxy acid, and what makes it such a notable topical? This guide explains the benefits, side effects, different types of beta hydroxy acids, and offer some recommendations for beta hydroxy products for skin and scalp problems.

What is BHA or beta hydroxy acid?

BHA or beta hydroxy acid is 1 of 2 of the better known hydroxy acids available in skincare for improving skin texture, speeding up skin cell renewal, and cleaning out pores of acne etc. The other hydroxy acid is AHA or alpha hydroxy acid. To learn more about AHAs, read our guide to AHAs or alpha hydroxy acids here.

Unlike AHAs which are water soluble, beta hydroxy acids are oil soluble. This means that they are exfoliate the topmost layer of your skin and also penetrate deeper and exfoliate extra oil build up in your pores and breaking deep set comedones (bumps under your skin that will become acne). This makes BHAs great for treating whiteheads, and especially blackheads.

BHAs have no humectant properties and can be drying so they are great for people with oily skin because they don’t make your face more oily.

BHAs also do not increase photosensitivity. You can use BHAs even if you don’t wear sunscreen daily without making your skin more susceptible to sun damage.

Beta hydroxy acid is also has anti inflammatory and antimicrobial properties that make it a great acne treatment. Many people who report AHAs to be too harsh in that they irritate their skin find that BHAs are a gentler way to tackle acne. Certain BHAs like salicylic acid can reduce acne inflammation without causing irritation. So what makes BHAs gentler than AHAs?

The more concentrated an AHA or alpha hydroxy acid, the more powerful and penetrative it is. In contrast, beta hydroxy acids are most effective at very low concentrations. BHAs at only 2% or 4% concentrations work best to exfoliate dead skin, clean out your pores, and act as an anti inflammatory or anti bacterial.

This also makes beta hydroxy acid an ideal ingredient for a lot of different kinds of skin care, from lotion or cleanser to toners or mouthwash. You’ll even find it in shampoos and conditioner to deal with scalp issues like dandruff or seborrheic dermatitis. Other uses for beta hydroxy acid are as a preservative, hair conditioner, skin conditioner, and an antiseptic.

Beta hydroxy acids are a truly versatile skincare ingredient with multipurpose usage. And nearly anyone can use it for a host of skin or scalp issues because it works best at low dosages and so is a gentle product.

While it works best at low dosages, it also better benefits your skin or scalp if you leave it on for some time before rinsing it off. The duration of time can vary with product and use. However, depending on what you’re using the BHA for, leaving it on for 5 to 30 minutes helps your skin absorb it better and take advantage of everything beta hydroxy acid has to offer.

What are the benefits of BHA?

How does BHA treat acne

Because beta hydroxy acid is oil soluble, it penetrates deeper than your skin’s surface skin and can clean out clogged pores that cause acne. Studies show that BHAs like salicylic acid are more effective and less irritating than AHAs in tackling whiteheads, blackheads, and acne.

In one study comparing the two side by side, 20 patients were recruited to use a BHA on one side of their face and an AHA on the other side of their face for 6 total treatments in 8 weeks. The results:

Both chemical peels were significantly effective by the second treatment (p<.05) and there were no significant differences in effectiveness between the two peels. At 2 months posttreatment, the salicylic acid peel had sustained effectiveness. More adverse events were reported with the glycolic acid peel after the initial treatment. [source: Kessler E1, Flanagan K, Chia C, Rogers C, Glaser DA. (2014) J Cosmet Dermatol.]

The patients used a low concentration of salicylic acid in this study and the AHA used was a higher concentration. Still, the BHA showed longer lasting results in tackling acne and was a gentler treatment for acne patients.

This is not to say that there is no place for using an AHA or using a BHA and an AHA together in your skincare routine. But to determine if you could benefit from an AHA, you’ll need to understand its benefits and side effects first. Use our guide to AHAs to learn more about alpha hydroxy acids.

How does BHA treat hyperpigmentation or inflammation?

Beta hydroxy acid also helps tackle inflammation caused by acne and hyperpigmentation caused by acne or other pigmentation on the skin’s surface. This is also known as post inflammatory hyperpigmentation or PIH or melasma.

Like AHAs, beta hydroxy acid helps speed up the skin cell renewal at the skin’s surface. This helps remove hyperpigmented skin layers for newer skin layers. AHAs may be more effective in this but beta hydroxy acids also show good results.

In one study, 45 patients with post inflammatory hyperpigmentation were treated with a retinoid called tretinoin and salicylic acid, a beta hydroxy acid. They were divided into groups with one group only using salicylic acid, another group on using tretinoin, and a third group using both in combination. The results of that study:

Combination of salicylic acid peel and topical tretinoin treatment showed significant clinical improvement of PIH than each treatment alone with no complications. [source: Mohamed Ali BM, Gheida SF, El Mahdy NA, Sadek SN. (2017) J Cosmet Dermatol. ]

The groups that were using only salicylic acid or only tretinoin did not see notable results in reducing their post inflammatory hyperpigmentation. This is great evidence that salicylic in combination, with in this case tretinoin, can act as a powerful treatment to reducing post inflammatory hyperpigmentation.

Those of you who used to have acne and are now dealing with the aftermath know how difficult it is to reduce the post inflammatory hyperpigmentation to have a truly clear face, without acne and without acne scars and pigmentation. So this study is great news for people with post inflammatory hyperpigmentation.

How does BHA treat dandruff?

As beta hydroxy acid helps remove the top most layers of skin, it can also help treat dandruff on the scalp in the same way. Given the antibacterial, anti inflammatory, and the exfoliating properties of beta hydroxy acids, they can act to soothe itching and reduce dandruff, redness, and flaking.

One study pitted a shampoo with salicylic acid against a shampoo with zinc pyrithione, a popular ingredient in dandruff shampoos. The results:

Both shampoos were highly effective in reducing the dandruff. The combination of piroctone olamine and salicylic acid appeared to be slightly more effective than zinc pyrithione in reducing the severity and area affected by the scaling. [source: Lodén M1, Wessman C. (2000). Cutis]

So salicylic acid can be as effective, if not more, than a zinc pyrithione in reducing dandruff. Zinc pyrithione is certainly more popular in dandruff shampoos today. Many people also find it is very harsh on their hair, but with not knowing of another alternative, continue to use it. Salicylic acid is gentler on the scalp without losing effectiveness and so could be a better option for you if you suffer from dandruff.

How to use a BHA?

Beta hydroxy acid is an active, which means that it is an ingredient that has direct active action on the skin. Other actives include alpha hydroxy acids (AHA), Vitamin C, and Vitamin A (retinoids and retinol).

There is some controversy over this, but we believe that to benefit from an active, you should leave it on your skin for a short period of time before applying further products or washing it off/out. This time period allows the acid to make contact and penetrate your skin and do what it is intended. If you wash it off, you may not have allowed enough time for the acid to penetrate into pores.

BHAs work best in a low pH environment. When you add more products on top, you may change the pH of your skin to less acidic and so make the BHA less effective. If you’re using a BHA as a skincare product, you can even use pH adjusting toners to make sure your skin’s surface has an acidic environment when you apply your BHA for maximum benefit. We’ve linked some pH adjusting toners that help with this at the end of this guide, if you’re interested in those.

That’s essentially a very short and summed up explanation of how to use BHA. We’ll write a longer post on this and link it here when it’s ready if you’re interested in real studies that show the effectiveness of BHA wait times in low pHs.

So to that end, you’ll notice on dandruff shampoos, the directions will ask you to leave it on your scalp for a few minutes before washing it off. You may also notice skincare products with beta hydroxy acids will ask you to wait 5 to 30 minutes before applying the rest of your skincare routine or makeup routine. This is for good reason and you’ll see greater benefits to your skin if you give the product that wait time to work on your skin.

BHA side effects

While BHAs have been shown to be less irritating than AHAs and other actives, they can still have some adverse side effects.

Some people can experience redness, stinging/burning, itching, and general skin irritation after using beta hydroxy acid at certain concentrations.

This can be avoided by finding a concentration that works for you. Various formulas will have different concentrations and type of beta hydroxy acid. Unless you’re allergic to this ingredient, most people can find a beta hydroxy acid that works for them. If you’re unsure where to start, find a low concentration to use and then build up from there if you don’t know notice any side effects.

Also, please patch test if you’ve never used a beta hydroxy acid before. You can patch test on your neck or the inside of your elbow where the skin is soft and hairless. If you experience any of the above side effects during your patch test, there are good chances that you will feel that irritation on your face as well. You can look at a different product with a lower concentration and try again.

What’s the difference between BHA and AHA?

You may have already figured out most of the differences between beta and alpha hydroxy acids, but here’s a quick summary in case you’re unclear on any of the following:

Oil vs water soluble

AHAs are water soluble and attract water to your skin and are great for dehydrated skin. BHAs are oil soluble, can be drying, and are great for oily skin. However, anyone with any skin type can add either to their nighttime routine (when it doesn’t matter if your skin looks oily, or you can layer moisturizers on top in abundance) and enjoy their benefits.

Sun sensitivity

AHAs will make your skin more photosensitivity and BHAs will not. If you’re lazy about wearing sunscreen or do not want to wear sunscreen, you can use beta hydroxy acids without worrying about making your skin extra sensitive to the sun and sun damage.

Wrinkles and fine lines

Both AHAs and BHAs exfoliate your skin, and so both can help reduce wrinkles and fine lines. While AHA is a much strong exfoliator for wrinkles and fine lines, you’ll notice some improvement with your skin texture and pigmentation with a BHA as well.

Hyperpigmentation and inflammation

BHAs are gentler than AHAs and so are less irritating. BHA has been shown to be effective treatment for hyperpigmentation and inflammation caused by acne. However, both can be also used together to improve pigmentation, skin texture, and renew your skin.

What are the different types of BHAs?

The most popular form of BHA we find in skincare and haircare products is salicylic acid.

There are also derivatives of salicylic acid like salicylate, betaine salicylate, and sodium salicylate.

Other less common forms of BHA include willow bark extract, beta hydroxybutanoic acid, tropic acid, and trethocanic acid.

If you enjoy the benefits of any of these beta hydroxy acids, you can also look at azaelic acid. While it is neither an AHA or a BHA, it is an active ingredient that offers many of the same benefits like improvement pigmentation, inflammation, acne, and skin texture like a BHA. Many people find that it is a BHA amplified and at lower doses/percentages, it is similarly gentle on the skin.

BHA Product Recommendations

Here are some of our tried and tested recommendations for products with beta hydroxy acid for skincare and for dandruff. You may not find these at a drugstore, but they’re all online. Since BHA is best used at a low concentration, there are many beta hydroxy acid products available over the counter with no need for a prescription.

Since BHAs are pH sensitive, you can also choose to use a pH adjusting toner before you apply your skincare. In the next section, see our recommendations for affordable pH toners.

Salicylic acid serums for skincare – acne, hyperpigmentation, inflammation

1.COSRX BHA Blackhead Power Liquid

This is one of the most gentle BHAs we have tried. The active ingredients include alix Alba (Willow) Bark Water, Butylene Glycol, and Betaine Salicylate at 4% which is the BHA derivative. This is an Asian Beauty product by COSRX, a well-reviewed dependable Korean brand. Highly recommend.

Read more reviews of Cosrx BHA Blackhead Power Liquid here.

2. Paula’s Choice Skin Perfecting 2% BHA Liquid

Another great go to BHA with 2% salicylic acid by Paula’s Choice, a US based brand. Paula’s choice is a popular brand that offers a host of skincare products that aren’t just good markting but also effective. We have found that Paula’s Choice Skin Perfecting 2% BHA Liquid is particularly good at eradicating blackheads on the nose or chin area.

Read more reviews of Paula’s Choice Skin Perfecting 2% BHA Liquid here.

3. Skin Medica AHA BHA cream

This is a AHA and BHA combination product and so requires daily suncreen use if you want to use it. It should also be used as part of your night time routine. Skin Medica combines a 30% AHA solution with a 2% bha in the form of salicylic acid. It can be used as a 10 minute mask and then washed off or kept on as part of layered night time routine.

We’ve found that with a few uses, there is a noticed increased brightness, hydration, and a visible reduction of acne scars or sun damage. There is no smell to the product and the cream consistency feels rich yet absorbs quickly.

Read more reviews of Skin Medica AHA BHA cream here.

Salicylic acid face washes

Face washes with salicylic acid as an ingredient are very popular, esp for those who suffer from acne. They’re seemingly easy to use and can be inserted into nearly anyone’s evening or morning routine because a face wash is easier to use than a serum that requires a wait time. But the wait time is the also reason we wouldn’t recommend a lot of salicylic acid face washes over a serum or lotion. A face wash doesn’t give the salicylic acid a lot contact time on your skin to act. As we discussed in this guide, the contact time allows the acid to work and penetrate your skin. So between a face wash or a serum/lotion, we recommend using a serum/lotion that you leave on your skin for an extended period.

There is one group that could benefit from a face wash – those of you with sensitive skin who cannot tolerate acids on your skin. A salicylic acid face wash can still allow for short term contact, which should not irritate your skin or irritate it less. Here are a few popular choices:

1. Neutrogena Oil-Free Acne Face Wash With Salicylic Acid

2. CeraVe Renewing SA Cleanser 8 oz Salicylic Acid Cleanser

3. Philosophy Clear Days Ahead Oil-Free Salicylic Acid Acne Treatment Cleanser

Salicylic acid shampoo for dandruff

If you’re looking for a dandruff shampoo with a gentle BHA to help reduce redness, itch, and flaking, these shampoos utilize salicylic acid and its derivatives to target dandruff without stripping your hair of its moisture:

1. Neutrogena T Sal Therapeutic Shampoo – Has 3% salicylic acid

2. Selsun Blue Naturals Dandruff Shampoo – Has 3% salicylic acid

3. Avalon Organics Anti Dandruff Shampoo – Has 2% salicylic acid

4. MG217 Psoriasis Shampoo and Conditioner – Has 3% Salicylic Acid

ph adjusting toners

Want to reap the full benefits of a BHA in your skincare routine by making sure your skin is at the correct pH level for your BHA? You can use one of these toners to prep your skin after cleanser, and just a few minutes before applying your BHA

1. COSRX Natural BHA Skin Returning A-Sol

2. MIZON Aha & Bha Daily Clean Toner

Azaelic acid

Intrigued by our mention of Azaelic acid as a stronger better BHA-like acid? Azaelic acid is far more popular as a drugstore produce in Europe than in the Americas or Asia but is gaining in popularity as people find out about its amazing skin benefits. We have found that Azaelic acid does nearly everything a BHA does but with even greater results.

Unlike BHA, the higher the percentage of Azaelic acid the stronger it is. However, it is best to start with a lower percentage and build your way up, because otherwise you may experience several peeling or can end up with a damaged moisture barrier.

Here are some products you can try for azaelic acid:

1. Curology – offers a formulation tailored to your skin and issues with a focus on anti-acne and anti-aging. It’s essentially a telederm service in which you get a prescription after you upload some photos of your skin. They will start you off with a gentle low concentration formula to make sure you don’t irritate your skin, and if you feel that it is going well then you can check in with your assigned dermatology provider to up your prescription in a few weeks.

It’s also very cost friendly, averaging out to $19.99/month for a tailored formulation for your skin. If you want to try Curology, you can use this link to try it for 1 month for free.

2. Ecological Formulas Melazepam Cream – 20% azaelic acid

3. GIGI Bioplasma Azelaic Cream – 15% azaelic acid