Cosrx BHA Power Liquid Exfoliant Review & My Descent Into BHA Research Madness

This has been a difficult post.  It was supposed to be merely a review of the Cosrx BHA Blackhead Power Liquid with a delicious little snack science on the side, like I did in Milky Dress Vita C+ Powder Review & It's Time to Get Nerdy About Vitamin C. Fun, crisp, & fluffy, with a satisfying aftertaste.

Unfortunately, this was not to be; I've spent days hunting down studies, tracking the muddled pawprints of sources in roving bands of reference herds, stalking my prey through stacks of marginally related papers, and all I've managed to uncover is some seedy research practices and what appears to be a multi-decade ongoing game of academic telephone.

Thankfully, there's more to products than just their INCI profile, and having gone through a good four or so empties of the Cosrx BHA Blackhead Power Liquid, a daily BHA (beta hydroxy acid) chemical exfoliant, I feel confident in discussing my personal experiences with this product even if the exact details of its scientific pedigree remains murky.

Cosrx BHA Blackhead Power Liquid beta hydroxy acid exfoliant
Emptying a bottle and cracking into a fresh one is so satisfying!
Ultimately, reviews are (or should be) our thoughts on products that we've used, and I've certainly used this enough, by both time and volume, to be ready to review it; I just never did so as there's already excellent reviews of this product out there, such as fellow Snailcast podcaster Fifty Shades of Snail, and Sheryll of The Wanderlust Project.  However, I was keen to do another review-with-a-slice-of-science post, since I enjoyed the last one so much, so I decided to take advantage of our household's as-yet-unexpired university library subscription and hit the research papers.  I sort of regret that, but we'll plumb those depths of despair later.

In this post:

  • Why chemical exfoliants are swoon-worthy
  • Product details
  • Ingredients & short review
  • A research overview on the benefits of BHA and salicylic acid
    • BHAs don't do what we think they do
    • Why use BHA at all?
    • Photoprotection, not photosensitivity
    • Does it work on acne?
  • Final thoughts

I'm going to keep the review portion short and sweet, so I can focus on the results of my research efforts; this way you can bail out of the rabbit hole if you're not into descending into nerdy madness.

Just as a quick reminder: this blog uses both affiliate and non-affiliate links, and if you choose to click the fomer before you shop, your purchase may contribute a tiny amount to the maintenance of this blog.  See full details at the end of this post! #receipts

Why chemical exfoliants are swoon-worthy

Having read upward of a dozen papers recently, I can say with confidence that hydroxy acid exfoliants (like our BHA in this review) work by weakening the bonds gluing your skin cells together.  That might sound like a terrible idea, but it's actually brilliant; if you've ever soaked a pot with burned-on food residue to loosen it, instead of violently scraping away and damaging the pot, you've experienced the same kind of mechanism.

There are many, many forms of acid exfoliants, which means that you may be overwhelmed with options when trying to choose one; the upside is that you have a lot of alternative options if some of the standard ones don't work for you.  For a basic primer on acid exfoliant types, I recommend checking out Hoojoo's post on AHAs and BHAs-- if podcasts are more your style, acids were the topic of a recent Snailcast episode.

If you're not sure where an acid exfoliant would go in your skincare routine, I recommend checking out Putting your products in order, including pH dependent acids.

Product details

Full product name: Cosrx BHA Blackhead Power Liquid
Purpose: A chemical exfoliant, specifically BHA (beta hydroxy acid) in a low concentration at a pH suitable for exfoliation, making it weak but gentle enough for OTC use.
Scent: Er.  I'll need to go sniff it; it's not pleasant but it's very forgettable.
Texture: A fluid gel that spreads easily and can be a bit sticky.
Quantity: 100ml
Rating:  4/5, I've tried other BHAs and returned to this one over and over.
Where to get it:   Amazon | eBay | Jolse | Bisou Beauty Bar  | KoreaDepart | RoseRoseShop
Repurchase:  Repurchased many times; I'm on my 5th bottle.

Ingredients & short review

According to Cosrx's EN site, the ingredients in the BHA Blackhead Power Liquid are:
Salix Alba (Willow) Bark Water, Butylene Glycol, Betaine Salicylate, Niacinamide, 1,2-Hexanediol, Arginine, Panthenol, Sodium Hyaluronate, Xanthan Gum, Ethyl Hexanediol
Cosrx has a reputation among K-Beauty fans for having simple, uncluttered ingredients lists.  There are no significant flags in this product per a Cosdna analysis, and it's got a small but solid lineup of functional ingredients.  Korea has harsh restrictions on OTC sales of salicylic acid, the most commonly used and studied BHA, which is something to keep in mind if you're looking for chemical exfoliants.  Acid exfoliants are usually dependent on both concentration and pH, which means you need to be aware of both when choosing a product.

Don't laugh: this was my emergency setup
 when testing my digital pH meter
As far as I know, there is currently one study that supports salicylic absorption at a higher pH; but absorption doesn't necessarily translate to effect.  Having spent the last few days reading study after study that places the salicylic acid solutions actually used in the studies measuring the effects on human skin, at around pH 3.5 or lower (I've seen the upper range capped at 4.2 elsewhere), I'm going to stick with that until something compelling comes along.  (Check out Labmuffin's post for more details on the relevance of pH to acid exfoliation.)

Information about the concentration and pH is easier to find in western products, from what I've experienced, which is why you'll note that many K-Beauty bloggers will have hybrid routines featuring western acids + Asian hydrators, creams, and sunscreens.

Korea restricts OTC salicylic acid to 0.5% or less; this product sidesteps that by using betaine salicylate in an equivalent concentration (4%) to the the 2% salicylic acid found to be effective in clinical studies. (More on that later)

In addition to this gentler form of beta hydroxy acid (formed by combining betaine and salicylic acid), this product also contains niacinamide and hyaluronic acid, which are known for whitening (brightening, not bleaching) and hydrating (humectant) benefits respectively.

That makes sense considering my experience with the product: it was non-irritating and gentle enough for twice-daily use OR as one active in a weekly lineup that featured other actives, it loosened sebaceous filaments, blackheads, and clogged pores from my skin, allowing them to easily slide out during cleansing.  I'll get into this later, but from my dive into the studies on salicylic acid, one of the ways which BHA has been observed to impact acne prevention/treatment is by affecting the development of pore clogs (microcomedones), and "non-inflamed" breakouts, like blackheads (open comedones) and whiteheads (closed comedones) rather than the terrifying later forms of acne which I urge you not to google.

In addition to keeping my pores clean (at least cleaner vs skipping a BHA or nuclear option like a retinoid or azelaic acid) and therefore forestalling non-hormonal breakouts, the BHA Blackhead Power Liquid also lightly smoothed my skin without drying it out, and in fact it was hydrating enough that during the humid summer months, I haven't wanted to use anything but a low-pH cleanser, pH toner, and this BHA.  If I went outside, my routine would balloon into essences and serums and primers and sunscreens, but for a bare minimum, indoors-all-day-until-nightfall routine, this was pretty much it.

Left: my daily routine for the last week, right: my pretty Sulwhasoo cushion which was a recent giveaway prize
As I've mentioned in previous posts, I prefer to use a pH-adjusting toner to 'boost' the impact of my weak acids, such as this BHA.  I've tried other (stronger) BHAs, including a 3% serum from MUAC, and the iconic Stridex in the red box (which I purchased from Amazon, but it's also available in Walmart, Walgreens, etc.) and I found them to be much, much harsher and more irritating on my skin without being more effective.  For that reason, I've returned back to the Cosrx BHA over and over.

When I don't use it, I notice a difference in how quickly/easily my skin becomes clogged, and I've been very satisfied with the alternatives.  I'm currently awaiting a shipment of western BHA products, and will likely do a side-by-side comparison of them.  Unless I'm wowed and amazed, I'll continue purchasing the Cosrx  BHA for the foreseeable future.

Where to get the Cosrx BHA Blackhead Power Liquid:  Amazon  | eBay | Jolse  | Bisou Beauty Bar  | KoreaDepart | RoseRoseShop

Warning, beyond this point lies gratuitous, non-mind-safe levels nerdiness, you have been warned!

A research overview on the benefits of BHA and salicylic acid

I've actually completely cut what I had planned for this section, and will be posting it as a stand-alone post later.  After throwing myself into the available research on the skin benefits of BHAs and salicylic acid, I've come to some troubling conclusions about the reliability of sources.  However, there are a few SA (salicylic acid) benefits that I am reasonably confident including here.

BHAs don't do what we think they do

Salicylic acid is a keratolytic, which means that it exfoliates layers of skin.  I was not expecting this; I've been hearing from casual sources for years that AHA (like glycolic acid) was the go-to acid for desquamation (a fancy term for "descaling/peeling of the layers of the skin") which thins the skin, releasing trapped comedo demons, loosens skin flakes, and smoothes the texture of the skin.  As it turns out, Salicylic does the same thing[1] which would be logical considering that it's technically an AHA, but unlike glycolic acid (the OG of AHAs), salicylic acid is a "phenolic, hydrophobic, lipophilic compound [...] chemically unrelated to the AHAs."[2]  With the exception of one publication, all others referred to SA as the most well-known BHA, and that's why it's taking center stage here as the BHA of choice for our research excursion.

Of all the studies I read, I did not see any compelling evidence that indicated it was an effective anti-acne treatment due to anti-inflammatory or anti-bacterial properties.  Over and over, the primary driver for its effects against acne lesions was identified, at least by the authors, as being related to its keratolytic properties.  This was hugely disappointing and not at all what I was expecting.

Why use BHA at all?

So if SA does little else more than 'desquamate like an AHA', what's the point in using it?  It goes back to the part about "chemically unrelated to the AHAs"; even if SA gets you to the same place, it takes a different route.  Unlike glycolic acid, "Salicylic acid is unique among the hydroxy acids, because it can enter the milieu of the sebaceous unit, inducing exfoliation in the oily areas of the face."[2]  Translation: SA has no issues powering through the oily goo on your skin and in your pores, but it acts like an AHA all the same.  

I found no references to it 'dissolving' the oil in your pores, just that it's able to do it's AHA peeling business without becoming cockblocked by the presence of oil like a regular AHA would:
On the other hand, AHAs are unable to exfoliate optimally in the oily areas of the face, such as the central forehead, nose, and chin. Thus their activity in the treatment of acne is not as great, nor do they produce peeling in oily complected individuals unless the face has been thoroughly degreased.[2]
There are other benefits to peeling via SA instead of glycolic acid, namely photosensitivity.  Unlike glycolic acid, SA does not increase photosensitivity to the sun[3], and this is especially important if you're at high risk of sun damage due to your Fitzpatrick type, amount of sun exposure, sensitivity to sunscreen filters, etc.

Photoprotection, not photosensitivity

One of the only positive-yet-unexpected benefits I unearthed is a tantalizing implication of a photoprotective effect: "SA at 4% showed a photoprotective activity, reducing the carcinogenicity of [Solar simulated radiation]." as well as having a "pronounced filter effect when applied prior to UVB exposure" in a study on UVB therapy for psoriasis.[3]  Sadly, OTC products are limited by the FDA to concentrations under 3%, so it has little relevance to a daily BHA exfoliant!

Still, it's good to know that it doesn't have the increased photosensitization risk that glycolic acid does, but it's important to note that it's still keratolytic.  That means it's thinning your skin by coming for your skin cell layers, and thinner skin = more susceptible to sun damage.[4]  So no skipping your sunscreen!

The last thing I wanted to mention in the 'murky with unknown practical application' section is that SA might just boost the penetration of your skincare goodies: "Salicylic Acid is reported to enhance percutaneous penetration of some agents (e.g., vitamin A)"[4]

Does it work on acne?

The short answer is: yes.  Keratolytics do, in general.  They work by thinning the skin, including over closed comedones (i.e. whiteheads and clogs that haven't come to a head) so the face demons can escape.  Even if solid sources for the supposed anti-inflammatory and anti-microbial properties of SA are suspiciously absent, there are a few studies out there with clinical trials on the effect of SA on acne in concentrations available OTC.

This is important, because most of the drool-worthy studies on salicylic acid out there, and the lion's share of the materials, are about heavy-duty chemical peels, not daily exfoliants.  In The benefit of 2% salicylic acid lotion in acne a placebo-controlled study (Eady et al, 1996) the authors conducted a clinical trial of 2% SA lotion infused pads as treatment of mild to moderate acne.  The study was 12 weeks long, finished with 99 participants, who were university students between the ages of 16-25.  It was a stratified, randomized, double-blind, parallel-group, placebo-controlled study.  When I asked Dr. Mr. The Pear for his thoughts on the relative e-peen of such a study, he remarked that it's a "complicated design" but refused to comment on whether that's a good thing as this isn't his particular flavour of science.

Unfortunately, the study is difficult to interpret as it doesn't use practical measurements for effect size, it uses p-values, which is a fresh kind of hell of which I was unaware until Lab Muffin gave me a crash course.  If you want to plumb the depths of why p-values are a bane, google 'p-hacking' and prepare to be enraged.  I'll get into the shadiness I uncovered in another post, but Eady et al state their study results showed "conclusively the clinical superiority of salicylic acid pads compared with placebo."

Per this study, at first SA had an effect on baby acne imps, but not the full-fledged face demons.  By the end of the study, the population of facial hellbeasts had decreased overall, demon and imp alike, and they suggest this is due to SA dealing with them in imp form, before they managed to erupt into their final terrifying form.

If you've ever seen me mention I use BHA to 'prevent' acne, this next bit should make perfect sense:
It is now accepted that inflamed lesions arise from noninflamed lesions 11, and our observation that the salicylic pads reduced the inflamed lesions at a later time-point fits this concept."[5]
You know what they say, "an ounce of prevention is worth a pound of cure!"

Final thoughts

Ultimately, what matters to me most is whether a product actually worked or not.  As someone with combination-oily, dehydrated skin that's clog-prone, keeping my pores clear of baby face demons is the easiest approach for me.  I'm disappointed to find there's so little out there on the non-exfoliation benefits of BHAs (such as the anti-aging) in the concentrations suited to practical use, but at least I know that I have a reliable, affordable, readily available BHA that works well for my skin.

Even if it doesn't have the pedigree I thought it did.

With that, I'm so, so done.  I'm absolutely exhausted and very ready to do a single-subject non-randomized, non-controlled, no-placebo study on how many drinks it takes for me to forget the pangs of this research.

Have you found an original scientific source on benefits of BHA or SA in OTC concentrations?  Hit me up on Facebook or Twitter and let me know!

Have something you'd like to share with me in general?  Snap a pic and tag me on Instagram at @snowwhiteandtheasianpear because I'd love to see it!

All the best,

Works Cited:

1. Alikhan, A. (2010). Keratolytic treatment of acne. In R. Baran, & H. I. Maibach (Eds.), Textbook of Cosmetic Dermatology, Fourth Edition (pp. 352-364). CRC Press.
2. Draelos, Z. D. (2000). α‐Hydroxy acids, β‐hydroxy acid, and other topical agents. Dermatologic Therapy, 13(2), 154-158.
3. Kornhauser, A., Coelho, S. G., & Hearing, V. J. (2010). Applications of hydroxy acids: classification, mechanisms, and photoactivity. Clin Cosmet Investig Dermatol, 3, 135-142.
4. Cosmetic Ingredient Review Expert Panel. (2003). Safety assessment of Salicylic Acid, Butyloctyl Salicylate, Calcium Salicylate, C12-15 Alkyl Salicylate, Capryloyl Salicylic Acid, Hexyldodecyl Salicylate, Isocetyl Salicylate, Isodecyl Salicylate, Magnesium Salicylate, MEA-Salicylate, Ethylhexyl Salicylate, Potassium Salicylate, Methyl Salicylate, Myristyl Salicylate, Sodium Salicylate, TEA-Salicylate, and Tridecyl Salicylate. International journal of toxicology, 22, 1.
5. Eady, E. A., Burke, B. M., Pulling, K., & Cunliffe, W. J. (1996). The benefit of 2% salicylic acid lotion in acne a placebo-controlled study. Journal of dermatological treatment, 7(2), 93-96.

Works Consulted:

Mills, O., Adler, D., & Verdicchio, R. (2007). Pharmacology of salicylic acid (SA) in acne vulgaris. Journal of the American Academy of Dermatology,56(2), AB22.
Kligman, D. (2001). Technologies for cutaneous exfoliation using salicylic acid. Dermatologic Therapy14(3), 225-227.
Schwarb, F. P., Gabard, B., Rufli, T., & Surber, C. (1999). Percutaneous absorption of salicylic acid in man after topical administration of three different formulations. Dermatology198(1), 44-51.
SHALITA, A. R. (1976). Acne vulgaris: current concepts in pathogenesis and treatment. International journal of dermatology15(3), 182-187.
Whitney, K. M., & Ditre, C. M. (2011). Management strategies for acne vulgaris. Clin Cosmet Investig Dermatol4, 41-53.
Okano, Y., Abe, Y., Masaki, H., Santhanam, U., Ichihashi, M., & Funasaka, Y. (2003). Biological effects of glycolic acid on dermal matrix metabolism mediated by dermal fibroblasts and epidermal keratinocytes. Experimental dermatology12(s2), 57-63.
Green, B. (2005). After 30 years… the future of hydroxyacids. Journal of cosmetic dermatology4(1), 44-45.
Ghosh, V. K., Nagore, D. H., Kadbhane, K. P., & Patil, M. J. (2011). Different approaches of alternative medicines in acne vulgaris treatment. Oriental Pharmacy & Experimental Medicine11(1), 1-9.
FETIL, E., Sebnem, O. Z. K. A., SOYAL, M. C., ILKNUR, T., ERDEM, Y., & GUNES, A. T. (2002). Effects of topical petrolatum and salicylic acid on the erythemogenicity of UVB. European Journal of Dermatology12(2), 154-6.

**Disclaimer: All products I review on my blog are 100% purchased with my own money, with a single exception of a press sample I tested & reviewed in 2015 which swore me off of them forever.  This blog contains  both affiliate and non-affiliate links, and clicking the former before you shop means that this blog may receive a small commission to assist in this blog supporting itself.  Please see my Contact Info & Disclaimer policy for more information.


  1. Thank You for the effort. This is such an informative and reader-friendly entry. The drinks are well deserved! :) Cheers !

  2. Damn, awesome job! I can only imagine how difficult it was to stay sane while analysing all those scientific papers. Even your post gave me way too much to think about and a minor headache (technically an AHA but chemically unrelated to the AHAs? whaaaat?).
    I don't really know what I'm talking about but I'm wondering... Salicylic acid is almost insoluble in water, but it's said to be soluble in alcohol and oils (I don't have scientific sources to confirm this, only information from a cosmetic ingredient supplier, a vague memory of a table of substances SA dissolves in and a jar of SA in my drawer that I could experiment with). I guess that it would make sense that besides inducing exfoliation SA mixes with the oily gunk in our pores, making it thinner and easier to remove, right? At the same time it would probably be "cockblocked" by water, the same way AHAs are by oil, because it's not soluble in water. This is how I understand it at least. You definitely deserve a drink. Cheers!

    1. that might be due to the molecules being polar and non-polar. Water is polar and therefore mixes well with other polar substances. alcohol molecules has a polar and non-polarside so it can mix with polar and non polar substances. Oil is non-polar and water is polar so that is why they can't b mixed.
      I don't know if SA is polar or non-polar or what it looks like on a molucelar level but based on your story it could mean it's non-polar or it has bot polar and non-polar properties (like alcohols).
      i have know idea if this helped or gave you another headache :P

  3. You got me inspired to work on my skincare routine and try these products. Thank you!

  4. I love your sense of humour, you crack me up yet keep me informed with all the nerdy stuff without boring me to death. So thank you.
    Coincidentally, I just purchased a bottle of CORSX Blackhead Power Liquid a few days. Perfect timing. And I love your blog.

  5. Hi dear,

    Many thanks for your post. I sooo appreciate your research efforts and the organised way you're building your post. You go gurl!

    I've been using this product religiously once a week for over 9 months but still, I couldnt appreciate significant changes.
    Good news is, I have far less blackheads but my pores look so dilated, bumpy and visible though (nothing I can do).

    The thing is, I'm not quite sure of the 'how to' and exact purpose T_T

    Is it meant to kinda loose down the gunk and push it outside your pores? I havent experienced wiping out vermicelli that would exit my nose pores lol

    After using that product, what would you do exactly?

    Usually, the following night, I use a clarisonic to coax the baddies out via vibrations. Or sometimes, I'd use a soft pore brush while travelling. But not sure this really penetrates the pores and oust the gunk...

    Many thanks in advance for your practical advices.


  6. Thanks for your research. I prefer reading blogs like yours, instead of scientific papers. I also have a more casual approach to testing products. First I got into the cult favorite P-50. Then I thought to try the Paula's Choice BHAs, then the CosRx BHA. Then the CosRX AHA, then their toner. People generally seem to suggest AHAs and BHAs are different enough to warrant using both. But having tried this and that, and alternating this and that, I've decided all I really need is the one CosRx BHA. I thought the toner was a keeper too, for the mornings when I didn't want to be making my skin all photosensitive, but pfft, looks like all I really need/ want is the one. This is good. I like things simple. Thanks again.

  7. Awesome and perfectly researched post. I do not comment often, but still I'm a frequent reader of your blog :). Just one point: salicylic acid belongs to the nonsteroid antiinflammatory drugs which is stated by quite a bunch of papers actually.There is actually a reason why One of the most used papers is by Higgs, Salmon, Handerson and Vane (PubMedID: PMID:3103135). If you'd like to read it let me know, I can send it to you. That's also the reason for the anti-inflammatory effect of Acetylsalycilic acid (Aspirin) after all.

    1. Yes indeed! In fact the night before I posted this (well technically really early that morning) I was reading about NSAIDs and the conversion to salicylic acid, etc. I'm aware of it having anti-inflammatory properties for internal use, and even checked into some studies about the possible benefits of applying it topically for pain relief instead of ingesting it. :) However, since there wasn't anything that was applicable to treating acne, which was the kind of anti-inflammatory I was looking for, I didn't get into any of those details. :) I knew it would be confusing enough already! ;)

    2. You're totally right, it is confusing and you probably really had a hard time writing it up all together. I think since they have not only anti-inflammatory properties but also anti-microbial properties they will work the same topically because their effect on what causes our pimples to inflamate. This makes them act calming on acne because it prevents the microbes to spread...anyways, great work and great article :*

  8. This was a really interesting read! I never thought that my CosRX BHA was essentially scientifically speaking an AHA. I also love it because it's so much more gentle than western alternatives and have seen a difference in acne appearance for the better.

    Sophie | MapleTreeBlog

  9. Thanks for your hard work!!

    By the way, my sister sent me this article, and I wonder how true...anyone can shed some light on this?

  10. You've got a knack for explaining this stuff conversationally! I too love the Cosrx BHA for being gentle and hydrating AND a nice little exfoliant.

    My issue with the Cosrx BHA -- which I use -- is that it has niacinamide, which is supposed to turn into irritating niacin when mixed with an acid... offhand do you know anything about that?


  11. Hi!

    Thankyou for posting this entry
    I've been going back and forth deciding which chemical exfoliant should I buy
    In the end, after reading your research, I decided to buy the COSRX BHA Blackhead Power Liquid!
    I hope it will work in my face hehe :)

    Anyway, I've got one question, will this acid exfoliant work even if we don't use a pH-adjusting toner?

    Thank you in advance and have a nice day!

  12. Great post! I'm a cosmetic formulator and I so enjoy acid science. The only thing that keeps me from buying the Cosrx BHA is the inclusion of niacinamide. I love me some niacinamide, but at a pH under 5.5 it converts to Nicotinic acid and can become pro-inflammatory. It's probably in such a minute amount as to not be a big issue, but I don't understand the inclusion of it here. I use the Paula's Choice Resist 2%, it's much better than her original 2%; the Resist is like water on the skin.

  13. Just keep in mind that if you're allergic to aspirin, you should avoid salicylic acid products as well. Learned that the hard way.

  14. You do it again by backing up beauty with science :) Thanks so much for the super in-depth post as always. You're one of the most adept writers I know of in the community.

  15. This was so interesting! I'm currently using Paula's Choice AHA and BHA and this post reinforces what I was thinking about them - namely that the effects don't seem that different from each other and that I think they're a bit too strong for my skin. I'm going to try cutting the AHA and I'm definitely going to try the COSRX soon!

    1. I think there's definitely a difference in effect based off my personal experience, namely that AHA lifts my CCs to the surface, and BHA loosens my pore clogs, but I think BHA exfoliates the skin more than people realize. If you feel like they're too strong for you (and the BHA is pretty strong-- I have not tried the AHA yet) you could definitely look at trying a more gentle acid. :D

  16. Hi! I am sorry if this post does not belong here 😅.. i am going to purchase mizon aha 8% peeling serum for my mum and you mentioned that you said if we use acids, our skin is going to be thinner. Does it mean that it is going to be more prone to tanning? Thank you 😍😘😘😍

    1. Yes, and AHA is also photosensitizing. If you are going to use exfoliants, a good sunscreen is definitely a must. :)

  17. Benzoyl peroxide has research backing up its effectiveness for erradicating acne causing bacteria in a few minutes. So I wash it off after I let it sit on areas of my face for a few minutes and haven't seen a pimple rear its head since ...... Drum roll***MAY

    1. That's awesome that it's working so well! :D

  18. Hey! Sorry to leave a comment on a relatively old-ish post, but I noticed in the photo that you posted at the top that the BHA liquid is slightly yellow tinged. I noticed that my COSRX BHA has also been changing colour since I purchased it earlier in 2016, and wanted to ask if this is normal/is the product still usable? I've been using it all the same but I'm wondering if I should stop because the colour shift indicates some kind of degradation of the product.

  19. Can you post a how to as well? I'm not sure I'm using it right.thanks!

  20. Apparently Cosrx has since updated the pH of their BHA Blackhead Power Liquid to 4.5 +- 0.5:


    With it already being a milder BHA to begin with, do you think it's still worth using with the much higher pH?

  21. Wow your blog is amazing! I love how you incorporate scientific research/thinking into your reviews and the science behind the ingredients!