Salicylic Acid (BHA): Literally Everything You Need to Know

by | Last Updated Aug 4, 2017 | Acne, Ingredients | 38 comments

Salicylic Acid (BHA), a.k.a the ingredient in all those acne washes that doesn’t work. Frustrating huh? Don’t blame the poor guy though. It’s not his fault.

He’s actually pretty awesome, only companies don’t formulate him properly so people think he sucks. But, that’s why we’re here — to make his life a little easier and boost up his coolness factor.

We’ll be discussing what salicylic acid is, its benefits, side effects, how to use it, and what products are properly formulated. Without further ado…

What is Salicylic Acid?

Salicylic Acid, often referred to as BHA (beta hydroxy acid), is a naturally occurring hormone produced by plants as a defense mechanism against environmental or pathogenic stress. (1It can be synthesized from Willow trees and brush, thus the term “willowbark extract” you might have seen in some cosmetic formulas.

willowbark extract

Dietary sources of Salicylic Acid (SA) are commonly found in fruits, vegetable, herbs, spices, tea, wine, fruit juice, and ketchup. It’s nutritional content may also play a role in lowering the risk of butthole cancer. (23)

I mean… colon cancer. Apologies.

As far as skincare products go, Salicylic Acid (SA) is pH dependent requiring an acidity level of 4 or lower to effectively exfoliate and treat acne at its maximum capacity. Anything higher reduces its potency, and a pH above 7 essentially renders it useless. (4) Which may be the reason you found that drugstore spot treatment as effective as your mom’s advice.

“Just wash your face, honey.”


  • Salicylic Acid Treats Acne.

Unlike most AHAs, SA is oil soluble allowing it to penetrate into pores and dissolve clogs. It also exfoliates superficially through desquamation of the stratum corneum. (5)

English translation = it removes dead skin cells from the outer most layer of skin.

It’s anti-inflammatory, anti-bacterial, a keratolytic, and prevents clogged pores meaning it addresses all major causes of acne. (6)

Multiple clinical trails have shown that using 0.5% to 2.0% Salicylic Acid pads (like Stridex in a red box) reduces the severity of acne, with some studies showing it’s even more effective than benzoyl peroxide. (7)

paula's choice 2% bha liquid

See on Amazon

The efficacy of Salicylic Acid peels has also been studied, with a couple clinical trials showing a 30% peel used every two weeks significantly decreases non-inflammatory and inflammatory acne (in other words, clogged pores in addition to swollen pimples). (8910) Cooler yet, the peels had minimal irritation and caused no changes to skin hydration, pH, and transepidermal water loss (TEWL).

With that said, I would highly advise that newbies DO NOT begin with chemical peels. So chill newbie, chill! That’s for the more experienced users who’ve become accustom to weaker BHAs. ;p

15% salicylic acid peel muac

The pH and formulation of SA has a huge impact on how well it works, with study results varying from little difference to 95% of patients seeing improvement. (11)

So again, if your using a BHA that that doesn’t have the proper pH you might be getting little benefit from it other than some anti-inflammatory properties. Sure, that can help some. But to really treat acne, you need to address far more than that.

The combination of ellagic and SA produces comparable results to 4% hydroquinone, a potent melanin-inhibiting prescription drug. (1213)

BHA is also suitable for darker skin tones, unlike AHA which could cause erythema or worsen hyperpigmentation under the right circumstances. (14) In fact, a study involving 25 people of color showed that 20% and 30% Salicylic Acid peels were effective against melasma and post inflammatory hyperpigmentation by resurfacing sun damaged skin. (151617)

The lightening capabilities of Salicylic acid peels has been replicated time and time again, and is suitable for lighter skinned folks too. (181920)

  • Salicylic Acid Has Anti-Aging Benefits.

SA may have some anti-wrinkle effects. This area has been less studied so take these next couple of studies with a grain of salt. The first, a study involving mice.

Yeah yeah, I already know what your thinking. “Rats? Rats? We’re not rats! How is this relevant to us dude?” I said take this information with grain of salt for a reason…

Anyway, a study involving mice showed that a 30% salicylic acid peel helped rebuild the connective tissue on the surface of skin, thereby reducing wrinkle depth.

As for the people studies — there’s evidence a derivative of SA called sodium salicylate has great anti-aging benefits. (21) It’s made by neutralizing SA with sodium hydroxide (lye), and on three different occasions has shown to significantly reduce wrinkles and skin roughness without irritation, making it a suitable ingredient for those with sensitive skin.

As you may know, sun protection is the most important defense against premature aging. Case in point — see what happened to this trunk driver. Luckily for us BHA doesn’t cause photosensitivity (i.e. increased sensitivity to the harmful effects of sun exposure) like AHAs do. In fact, it may even provide photoprotective properties!

 For example, salicylic acid peels have been shown to prevent tumor growth by removing sun damaged cells and reducing carcinogenicity. (22232425) BHA also inhibits UVB-induced sunburn cell formation, and has been recommended by researchers as a topical protectant against sun damage. (26)

Another study found that using 2.0% Salicylic Acid for 3.5 weeks didn’t increase erythema (redness), DNA damage, or susceptibility to sunburn. (27) The same did not apply to 10% glycolic acid.

Whether the inhibitory UVB benefits apply to Salicylic Acid peels remains unanswered, so err on the side of caution and use sun protection just in case. Wait, scratch that, you should be using sunscreen regardless of what you’re using. Use sunscreen! I’m watching you….

  • Salicylic Acid Treats Warts.

WARTS. It treats WARTS. Indeed, in one study 81% of patients were either cured or saw vast improvement after only two weeks of using 26% Salicylic Acid. (28) Other studies have had similar cure rates (about 70%).

A note on the percentage: 26% is chemical peel strength, not something to try out of the blue. If you decide to treat a wart this way, take proper precautionary measures and do your research first!

Side Effects:

BHA may be Irritating, cause dry skin, and if used excessively disrupt the acid mantle. (2930) Worst yet, skin that has a damaged moisture barrier absorbs SA more easily which could further exacerbate irritation. As a pair of researchers put it, BHA has “an inherent pH-related irritancy potential which is even more exacerbated on sensitive skin.” (31)

It’s very easy to overdue it with SA. People often have a more is better mentality, but with skincare it’s often the opposite: less is more. The trick is to have the willpower to not jump the gun and play the waiting game. Patience trumps impulsiveness. Skincare isn’t a sprint, but a marathon.

How to Use Salicylic Acid:

Introduce it slowly. Start using it once or twice weekly. The next week increase to three times. The following week, 4 times. Continue doing this until irritation in the form of dry skin, peeling, redness etc. beings rearing its head. The absolute most you should be using it is twice a day.

It’s not uncommon that BHA causes a “purging period” when acne gets worse initially. Don’t fret, this is simply the salicylic acid decongesting what was already there. Depending on how frequently you’re using it, the purging period should last 3-4 weeks maximum before subsiding.

As we’ve discussed earlier SA is pH dependent, so the order of it in your skincare routine matters very much. You want to use it right after cleanser and before moisturizer. Here’s a sample routine with the order of all things being considered.

Note: depending on what you incorporate some of these steps won’t apply to you, so adjust it accordingly.

  1. Oil cleansing method, or oil cleanser.
  2. Gentle pH-balanced cleanser (5.5 or below)
  3. Low pH serums or toner. Wait 20-30 minutes.
  4. Salicylic Acid (BHA). Wait 20-30 minutes.
  5. AHA (glycolic, lactic, mandelic). Wait 20-30 minutes.
  6. Vitamin C (SAP)
  7. Retinoids (Tretinoin [Retin-A], Retinol)
  8. Spot treatments or other actives (e.g. Benzoyl Peroxide, Azelaic Acid).
  9. Moisturizers.
  10. Occlusives (e.g. Vaseline, Aquaphor)

Product Recommendations:

Because a well-formulated BHA product may be hard to find when you’re just getting started on your skincare journey, here’s a list of products that have the proper pH needed to work.

Good for sensitive, dry, or dehydrated skin.Cosrx BHA Blackhead Power Liquid
Good for oily, tough skin. Avoid if you have sensitivities to malassezia!Paula's Choice Skin Perfecting 2% BHA Liquid
Good for normal to oily skin.Stridex Strength Medicated Pads

Alrighty, folks. That does it for salicylic acid. Hope you found this helpful!



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