Salicylic Acid for Skin Explained (34 Studies): Everything You Need to Know!
Aww, salicylic acid. 🤓 One of my all-time favorite ingredients with a longstanding history of scientific data to back its effectiveness.
Today, we’ll be summarizing all the relevant studies on this sexy lad in an easy, comprehensive manner. You’ll learn what it is, what it does for skin, possible side effects, how to use it — and most importantly, what products are formulated correctly so you don’t miss out on all the benefits!
Come on along now young grasshopper, let’s begin!
NOTE: here’s a table of contents you can use to skip ahead to any section.
Table of Contents
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. (1) It can be synthesized from willow trees and brush, thus the term “willowbark extract” you might have seen in some cosmetic formulas.
Dietary sources of salicylic acid are commonly found in fruits, vegetable, herbs, spices, tea, wine, fruit juice, and ketchup. Its nutritional content may also play a role in lowering the risk of butthole cancer. (2, 3)
I mean… colon cancer. Apologies.
As far as skincare products go, salicylic acid is pH dependent, requiring an acidity level of 4 or lower to optimally exfoliate and treat acne at its maximum capacity.
NOTE: click here if you don’t know what pH is.
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.”
Benefits of Salicylic Acid
Treats Acne
Unlike most AHAs, salicylic acid (BHA) 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) reduce the severity of acne, with some studies showing it’s even more effective than benzoyl peroxide. (7)
UPDATE 4/17/19: similarly, three other studies have found that salicylic acid cleansers “significantly” reduce acne lesions. (32, 33, 34) The first of which showed it was more effective than using a benzoyl peroxide wash. This has been true for me personally. In fact, I give all credit to CeraVe SA Wash for completely eliminating my body acne! 🙂
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). (8, 9, 10) 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
The pH and formulation of salicylic acid 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.
Treats Hyperpigmentation.
The combination of ellagic and salicylic acid produces comparable results to 4% hydroquinone, a potent melanin-inhibiting prescription drug. (12, 13)
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. (15, 16, 17)
The lightening capabilities of salicylic acid peels has been replicated time and time again, and is suitable for lighter skinned folks too. (18, 19, 20)
Prevents Aging.
Salicylic acid 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? We’re not rats! How is this relevant to us dude?” Unfortunately, it’s the best science we currently have :p
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 human studies — there’s evidence a derivative of salicylic acid called sodium salicylate has great anti-aging benefits. (21) It’s made by neutralizing salicylic acid 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. In fact, up to 80% of age-related wrinkling can be attributed to sun exposure. Case in point — look what happened to this truck driver over the span of his 28 year career!
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. (22, 23, 24, 25) 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….
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. (29, 30) Worst yet, skin that has a damaged moisture barrier absorbs salicylic acid 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 possible to overdue it with salicylic acid. People often have a more is better mentality, but with skincare it’s often the opposite: less is more. The trick is having the willpower to not jump the gun and play the waiting game. Patience trumps impulsiveness. Skincare isn’t a sprint. It’s 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. begins rearing its ugly 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 might last anywhere from 4 to 6 weeks before subsiding.
As we’ve discussed earlier, salicylic acid 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.
- Oil cleansing method, or oil cleanser.
- Gentle pH-balanced cleanser (5.5 or below)
- Low pH serums or toner. Wait 20-30 minutes.
- Salicylic Acid (BHA). Wait 20-30 minutes.
- AHA (glycolic, lactic, mandelic). Wait 20-30 minutes.
- Vitamin C (SAP)
- Retinoids (Tretinoin [Retin-A], Retinol)
- Spot treatments or other actives (e.g. Benzoyl Peroxide, Azelaic Acid).
- Moisturizers.
- 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. My personal favorites are the Humane BHA Toner and CeraVe SA Cleanser.
| 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 |
| Good for all skin types. Eliminated my body acne! 🙂 | CeraVe SA Cleanser |
| Good for all skin types, super gentle! (Personal favorite) | Humane BHA Toner |
Alrighty, folks. That does it for salicylic acid. Hope you found this helpful!
Cheers,
—f.c.
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Hi, f.c. I’ve been binge-reading your site for a week now! Thank you from the bottom of my heart for creating this wonderful blog. I just want to fully understand something about your instruction of introducing BHA for a newbie like me. Does “once a week” really mean only one use (morning or night) for a whole week? Or does it mean one-day use (morning & night) a week? I’m really sorry for this stupid question.
For those who still don’t have much success with salicylic acid, I think mandelic acid is a viable alternative worth mentioning here (or maybe in a separate post someday). As far as the hydroxy acids go I think it’s the most versatile. It’s an alpha-hydroxy-acid, but it’s unique among the AHA’s in that it’s partially lipid-soluble (although not as lipid-soluble as salicylic acid), so it does a bit of what a regular AHA does, and a bit of what salicylic acid does, and yet is gentler than both due to its larger molecular structure, which means it penetrates the skin more slowly and the exfoliation is more evenly distributed.
Another big selling point is that from the research I’ve looked into, it has a much stronger antibacterial effect against p.acnes than salicylic acid (which I believe is very weak as an antibacterial), and so many people might find it more effective for acne. So in that sense, it’s kind of like an AHA combined with a BHA combined with an antibacterial (like benzoyl peroxide, azelaic acid, etc.), all in one, and yet gentler than all of the above. What’s not to love?
The only downside is that, like all AHA’s, it does increase the skin’s sensitivity to the sun, but if you’re in the habit of regularly using sunscreen (as everyone should be) then this isn’t a concern.
My research led me to mandelic acid in particular after following the same path that had led me to PHA’s like gluconolactone — i.e., seeking out actives that are very effective but with minimal or no side effects like irritation, dryness, etc. The main benefits that mandelic acid has over PHA’s, for now, are that it has more product choices available and there’s a fair bit more research into its activity against acne. Alternating between both might become a staple of routine, once a suitable PHA product becomes available (or I finally have the confidence to formulate my own).
Just a heads-up, but a few months ago Silk Naturals reformulated their BHA toner to contain salicylic acid instead of willow bark extract, and it should be at the right pH (3.5-4.0). The ingredients are very similar to their AHA toner which is quite popular for being basic but gentle.
I haven’t tried their BHA myself but thought it’d be worth mentioning so people know they have an option for an alcohol-free, pH-correct salicylic acid exfoliant other than Paula’s Choice and Stridex.
Ok . This answers my question I asked you in the PC BHA post . I was using the Cosrx twice daily . I had zero irritation and only saw a mild flake or 2 on my nose . Face looked like a baby’s but until day 7 . Then Doug started working his way onto my chin . I’m hopping no homies follow . The weird thing is that I really don’t think I had anything to purge out . My pores are the clearest they’ve been since high school. I’ll just take a break for several days . Then I’ll reintroduce BHA twice a week . It was just so damn fun using the Cosrx BHA ! It made my face so soft and glowing . I’m impatient. Gotta slow it down or return to Pazzifacetonfieldville ???? Thanks again !!
Hi. Do you think using bha regularly for years would cause some side effects? Ive been using it hut now I am wondering how salicylic acid gets remived from the body once you applied it topically.
Hi! what if i don’t use any toner (sometimes i use a geranium floral water) after cleansing (my cleanser has a ph of 5.5) will the bha still be as effective ?
Hi, f.c. I’ve been binge-reading your site for a week now! Thank you from the bottom of my heart for creating this wonderful blog. I just want to fully understand something about your instruction of introducing BHA for a newbie like me. Does “once a week” really mean only one use (morning OR night) for a whole week? Or does it mean one-day use (morning AND night) a week? I’m really sorry for this stupid question.
Also, are you using BHA daily now? How many weeks did it take your skin to get use to it and allow for you use it daily?
I have been using Paula’s choice 2% skin perfecting for over a year and love the results. I use it once a day at night. I always wear sunscreen, but I will be in the tropics in a few weeks. Should I stop the BHA prior to traveling and all the sun exposure I will get? Just don’t want to do anything that might result in skin damage or irritation.
Hi there! I would like to know that does that mean cleansers that contain Salicylic Acid are actually…pointless? Since most of them don’t have pH as low as 4, and one of the low pH cleansers that contain Salicylic Acid (Betaine Salicylate) which is CosRX Low pH Good Morning Gel Cleanser also has a pH of 5 (should be higher if mixed with water I guess).
Does “purging” would still occur in this case?
Thank you in advance!
Do you find the different versions of the Paula’s Choice BHA to be less drying? I know they have the regular strength and the gel… do you have any experience with those?
What are your thoughts on Paula’s choice’s higher concentrations of BHA such as the 4% and 9%? I used to use the 2% lotion type daily, then I switched to the 4% 1-2 times per week. I feel like my skin has built up an SA tolerance and its not as effective anymore, could that be true? I have been contemplating getting the 9% and using it once a week.
hi! Thank you for your wonderful blog. I am from Austria and it is difficult to get the products you recommend, for example I would like to buy the stridex pads or the cosrx products but they are not availlable, the only availlable products are some paula’s choice products on amazon. Is there any other product with bha you would recommend for malassezia acne?
Hi. I just wanted to ask. I am using the neutrogena blackhead eliminating toner. It contains BHA(Salicylic acid) as well as gylcolic acid. Is it safe for me to use it twice everyday? And did i still need to use scrub to exfoliate my skin?
Hi. Just started using the cosrx BHA blackhead power liquid last week and I can see the purging effect. I got several white bumps all over my forehead and chin. I’m afraid this could go worse but just like you said, it could last 3 to 4 weeks. Did you also experience the purging? Thanks.
Could you recommend a different product for dry and sensitive skin (dermatitis) because the one you posted for that category skin (Corsx BHA) got very bad reviews. OR if you could provide me with a link to a website that gives acurate instructions on how to make your own Salicylic Acid concentrations. Thank you I know its asking a lot but would REALLY appreciate 🙂
you said that AHA aggravate erythema but in another post you said that AHA can treat/heal PIE. Can’t understand. hope that you can reply because I am finding a solution for my PIE. I suffer acne and PIE for 1 year. Hope you can help me.
Hi, I’m just curious as to whether I should use my hydrating toners before Salicylic acid or after.. does anyone know the answer?
I have a quick question about the cerave SA renewing cleanser. Since it exofliates and contains ceramides 1, 3, 6-II as well as hyaluronic acid, should i treat it like any other exfoliater and use it once a week? I have oily, sensitive, acne prone skin. And where in my routine should i use it?
Why not be a little less jokey and childish? It is actually great on content – thank you for that – but you mar it by talking down to the reader by using “
cutesy-pie” language. Frank Sternberger