Star Ingredient(s): AHAs and BHAs

By request from the awesome Angelanrenee of BeautyandtheCat’s Beauty Blog, it’s time to talk about chemical exfoliation!

Exfoliation in general is vital to achieving bright, smooth, and healthy-looking skin. Unless removed, dead skin cells will build up on the surface over time, leading to a dull, rough appearance; flakiness; and possibly clogged pores and breakouts. Like a lot of people, I enjoy using a scrub once in a while, but physical exfoliation isn’t something I recommend doing every day. In the first place, it can be messy and labor-intensive, at least compared to chemical exfoliation, and in the second place, too much physical exfoliation can be irritating and lead to broken capillaries. For that reason, I prefer chemical exfoliation for day-to-day maintenance.

There are two main categories of chemical exfoliants: alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs). AHAs and BHAs serve different purposes and work very well together as part of a well designed daily skin care routine. They should be approached with caution at first, though. Don’t start using both products at the same time, and don’t use them every day until you know your skin will tolerate them well. I suggest starting with an AHA and working your way up from once every other day to once a day, then twice a day if you can stand the wait time in the morning, which I personally can’t. Same goes for BHAs.

Paula's Choice and Stridex chemical exfoliants
My preferred chemical exfoliators are Western.

AHAs explained

Alpha hydroxy acids are water-soluble chemical exfoliants that help to exfoliate surface skin by dissolving the bonds between cells so that dead skin can shed more easily. It’s important to note that they don’t dissolve the dead skin itself. Nor do they work instantly, as I’ve heard some people claim. At daily use concentrations of between 5 and 10 percent, AHAs simply accelerate and optimize the skin renewal process.

AHAs are useful for:

  • Brightening skin
  • Making skin tone more even
  • Reducing hyperpigmentation caused by acne scarring
  • Reducing fine lines
  • Hydrating

AHA cautions and best practices

When using AHA products, sunscreen is extremely important. AHAs are photosensitizing, which means that they increase your skin’s sensitivity to the sun. If you use AHAs, even if you only apply them at night, sun exposure without adequate UV protection will lead to increased sun damage. You know that I already consider sunscreen absolutely essential for fighting wrinkles and maintaining healthy, youthful skin. It is even more essential when using AHAs. If you use AHAs but choose not to wear sunscreen, you’ll be undoing any benefits you might get from your AHA product.

As a final note, the pH of AHA products will make or break the product’s effectiveness. In order to exfoliate, AHA products must be at a pH between 3 and 4. If the pH is below 3, the product is too acidic, and you’ll run the risk of chemical burns (luckily, however, I’ve never heard of an AHA product with a sub-3 pH). If the pH is higher than 4, it just won’t work.

BHAs explained

Beta hydroxy acids (BHAs) are oil-soluble chemical exfoliants that behave in a similar fashion as AHAs but that are able to get down into pores in order to clear them out at a deeper level than AHAs, thanks to the oil solubility of BHAs. The most commonly known and used BHA is salicylic acid, which is apparently not actually a BHA, but for the purposes of a chemical exfoliation discussion, it might as well be. For daily use, BHAs are typically found in 2% concentrations but sometimes 4% as well. BHAs are useful for:

  • Clearing dirt, oil, and dead skin cells out of pores, especially the typically more visible ones on and around the T-zone
  • Reducing inflammation

BHA cautions and best practices

Like AHAs, BHA products must be at a pH of between 3 and 4 in order to work properly while still being safe for skin. While BHA products will still provide some anti-inflammatory benefits at higher pH levels, they will not be able to exfoliate or clear pores. Additionally, many people find BHAs drying, so make sure you have enough hydration and moisturization in your routine before trying out a BHA.

Using AHAs and BHAs together

Since AHAs and BHAs are effective for different skin concerns, many people, including me, choose to use both in the same routine. Here are some tips for doing so:

  • Use your AHAs and BHAs as soon after cleansing as possible. The closer they can be to bare skin, the more effective they will be, and since they’re pH-dependent, you won’t have to worry about whether the higher pH of other products will interfere with the acids’ exfoliating actions. I use them right after my vitamin C serum, since my vitamin C serum is also at a pH of between 3 and 4.
  • Use your BHA first, then your AHA. That way, the BHA can get deeper into blocked or dirty pores as well as prepare the rest of your face for your AHA.
  • After applying your acids, wait at least 20 minutes before applying the rest of your routine. That’s about as long as it takes for the acids to neutralize, so waiting will allow your AHA and BHA products to work to their maximum potential.
  • Don’t bother with AHA or BHA cleansers or other wash-off products. They don’t stay on the skin long enough to have any exfoliating effect and are most likely not at the correct pH, anyway.

Why do I use Western AHAs and BHAs instead of Asian ones?

I may be wrong about this, but it seems to me that AHA and BHA products have only recently begun to gain some popularity in the Korean skin care market. That is, at least, how it looks to me. Asian lines often focus more on scrubs, “peeling”-type products, and other forms of physical exfoliation. Lines like CosRX are starting to gain traction for their AHA and BHA products, however, and Mizon makes an AHA serum, which I’ve heard is effective and at the right pH, so I’m sure I’ll be trying out some Asian chemical exfoliants in the future. For now, however, I’ll be sticking to my Stridex pads for BHA and my Paula’s Choice gel for AHA.

I’ve tried to break AHAs and BHAs down into something easy to understand, but if you want to take a deeper dive into the chemistry behind chemical exfoliation, check out Hoojoo Beauty’s post on chemical exfoliation.

Do you use any chemical exfoliants, or do you prefer physical exfoliation? Why?


43 thoughts on “Star Ingredient(s): AHAs and BHAs

  1. Well this certainly gave me something to think about. I exfoliate almost daily with a scrub (not loyal to any certain brand). To add insult to injury I use the scrub in conjuntion with an exfoliating glove. It has never occured to me there might be a better option that would not only be more effective, but kinder to my old skin. Thanks!


      1. Such a great article thank you! But I have a lot of questions. Ok first, I know you said we can use BHAs and AHAs together from day to day or everyday, what If the instructions on the bottle say to use 2x 3x a week? Is it really safe to use everyday or should we follow the manufactures instructions?

        Second question, I use CERA VE SA renewal cream which already has lactic (lactose to be exact) and salcylic acid, it literally works great, but I also have a 10% lactic acid serum, would that be bad to use together?


  2. Woohoo! Thanks for the shoutout. You’re awesome. This is a handy explanation.

    I actually just got the PC 2% BHA Liquid as a sample in my Birchbox and am excited to try. Currently, I use Peter Thomas Roth 10% Glycolic Toner and UNT Ex White Laserwave (mandelic acid)–not in the same routine–and occasionally use Neova Reveal Exfoliator as a peel (pH is 2 but it’s only on for 3 minutes).



  3. thank you for this great explanation! now i am planning to try using bha. is it ok to use a toner too? should i use before or after bha?

    Liked by 1 person

    1. What kind of toner are you considering? You can use a pH-adjusting toner (usually you can identify these because they will have a little bit of AHA and BHA ingredients) before your BHA. A hydrating toner (like Hada Labo or the many first essences) will go after your acid step(s).


      1. Thanks for your reply 🙂 I have oily skin and large pores so I’m using Innisfree Persimmon pore toner. It has willow bark extract in it (not sure if is it BHA). I live in a hot and humid country so I need something more to reduce oiliness without irritating my skin.

        Liked by 1 person

  4. Okay, that looks like a decent prep toner. If the pH is 5.5 and you are not using a low pH cleanser, it will be good to use immediately after cleansing. If you have a good low pH cleanser, then use the toner after your acid steps. FYI willow bark extract will not exfoliate, but it will have anti-inflammatory effects).

    If you’re looking for somewhat stronger toners, COSRX and Mizon both make AHA/BHA toners that may work a bit better for you.


    1. Will the PH level got affected? I have combination to oily skin, and have very congested pores as well. Need to work on that pores and little pimples all the time.

      Liked by 1 person

  5. Here is my current night routine, can you tell me if they’re in the right order? Also looking for a good night moisturizer for oily, combo, sensitive skin with mild acne. Any personal recommendations??
    – cleanse
    – Mizon AHA/BHA toner
    – Cosrx AHA Whitehead Liquid
    – Missha First Treatment Essence
    – Hada Labo Toner Lotion
    – Moisturizer

    Liked by 1 person

  6. Hi,
    i want to ask if my night routine is right:
    Unt ex white laserwave serum
    cosrx Aha/bha toner
    cosrx advanced snail 95 all in one cream
    cosrx ultimate moisturizing honey overnight mask
    cosrx ULTIMATE nourishing rice overnight spa mask
    i am littel bit confused because the sail cream has a ph level of 5.8 and the essence a ph level of 6.0. But normally you would put the cream after the essence on right?

    Between the mask i put the one on which i need for the day(of course not both at the same time haha 🙂 )


  7. Hi there! I love your blog. It’s my daily skincare bible. I’m from the Philippines where it’s extremely hot and humid (SUNSCREEN!!! – I love Biore too BTW) and I use tretinoin. Can I use AHAs and BHAs with tret as well?


    1. Hiii! Yes, you can use AHA and BHA with tret but you must be very very careful as it’s quite easy to go overboard! I’ve been doing BHA on my nose only 1x every day and AHA about once every third day; I’m very nervous to go more than that!


  8. Hi, do you wait in between applying your bhas and ahas? I currently have both the aha and BHA from COSRX and I want to use them both in the same routine to combat acne but I’m not sure if I should use them on alternating days or use them together. If you do them together do you apply the aha immediately after the BHA? Or do you wait thirty minutes in between?


    1. Hi, I don’t use them together anymore (tretinoin complicates things!). When I did use them together, I’d wait anywhere from 5-15 minutes in between each layer. These days I do BHA every morning on my nose only, with about a 5-10 minute wait, and AHA every third night in the evening right after cleansing, also about 5-15 minute wait time.


  9. H! Thanks for this informative post! I read that you’re using a vitamin C serum with AHA and BHA… How’s your skin reacting to it? Wouldn’t that be a bit too strong? I read from another reference that these stuff can’t be combined, so I’m a bit apprehensive to combine them. I currently have C20 vitamin C serum, Cosrx AHA 7 whitehead power liquid, and the Cosrx BHA skin returning a-sol… They’re just collecting dust in my beauty cabinet because I don’t know how to use them! Could these be used altogether, and if so, how do you layer them (waiting time between each product)? Thanks!


    1. Hi! It is definitely wise to be cautious with actives like these. I was fine using all three before I started using tretinoin, but the combination became too much when I added that prescription active to my routine. I have a newer post explaining how I deal with my AHA and BHA now (instead of using both of them over my whole face, I only use them where needed–BHA on my nose and AHA on any sections that have spots to fade or bumps to smooth out, and I don’t do it every day, more like 3-4x a week).

      Some people, like me before Curology, do use all the products daily without problems, but it depends on your individual skin’s tolerance. If you were to use all your products together, I would do it like this: C20 -> AHA -> A-Sol.

      Another thing to keep in mind is that vitamin C persists in skin for quite a long time after application, so you don’t really need to use it every day to maintain good antioxidant levels. Once every other dayis fine too!


  10. Lady – you have NO IDEA WHAT YOU’RE TALKING ABOUT!

    Please go do some real research or get a medical degree before you being dishing out false skincare advice on the internet.

    You are basically just wasting you’re expensive Vitamin C product when you make that combo. See below and any other reputable websites for more info.

    “Vitamin C and alpha hydroxy acids. “They change the pH of vitamin C enough to destabilize it, making the antioxidant ineffective,” says David Bank, a dermatologist in Mount Kisco, New York. If you’re wearing a serum with glycolic acid, pick serums with heartier antioxidants, like green tea and resveratrol.”


    1. I’d be curious to know the mechanism by which an AHA is said to change the pH of vitamin C. Products like these are typically buffered, making changing their pH quite challenging especially with the very small amounts of products being added to each other. Unfortunately, there are enough doctors out there offering contradictory quotes to various publications that I’m hesitant to take one quote as particularly authoritative.

      Anecdotal evidence from people who use both AHAs and L-AA and see the results expected have me confident to continue using acids and vitamin C together.

      I did also find a couple of interesting articles on the topic:

      This study uses a combo of L-AA and glycolic acid to treat striae alba (stretch marks) with success:

      This brief post directly addresses the assertion that AHAs and L-AA can’t be used together:

      I always welcome questions and corrections, but I’d hope that people would do so respectfully and in the spirit of honest discussion. I’d be happy to look over any peer-reviewed studies published in bona fide scientific journals, but mainstream entertainment media like Allure is not a recognized scientific source.


      1. you used a 1998 article which if you actually read…. says nothing about whether using the vitamin C was effective…. rather, the glycolic itself could have been the sole thing that was helping the stretch marks on that side of the leg. This does nothing to negate my earlier statement that using BHA with AHA makes the vitamin C null and ineffective!!! So you ARE WASTING MONEY BY ADDING ON THE VIT C AT THE SAME TIME. Hellooooo.

        your second source is your very scholarly blog …. Im not sure how that is better than Allure?
        Also, Allure is extremely reputable in this case, given that I am not quoting a journalist, but rather the world reknown dermotologists that are answering their questions in the article.

        You provided 2 lame examples because there isnt info to support what youre saying. ANECDOTAL EVIDENCE???lol. Basically stop dishing out false ancedotal skincare advice and dont fool other people into wasting their money. If you want to do it, thats fine, but others should beware that youre not the expert you pretend to be.
        Have a nice day.


    2. Wow why do you have to be so rude though? her blog has helped so many people so you don’t know what your talking about. If she did happen to make one mistake, that doesn’t make her entire blog “misleading”. Also she was willing to take in advice, and did some research after you brought it up. And besides that, looks like her skin routine is doing good for her anyways. But she was willing to take your shitty advice in, and you were still being rude which is so uncalled for. Go write your own blog if your so savy with face products, oh maybe you do have your own blog and your just upset because it doesn’t have nearly as many followers….

      Liked by 1 person

  11. Hi Fiddy, thanks for the great post! And also, sorry you’re getting flak from the last poster. It’s amazing that people can be so rude simply because they’re sitting behind a screen and dont think that bloggers have feelings too. I believe strongly that all of us who read blogs like your’s, Tracy’s and Snow’s understand that you’re blogging about your personal experience with products, and your understanding of the research supporting your hypotheses and/or experience. Nowhere have you or any of the others ever said that you were experts. At every point you’ve all pointed out that you’re not derms and that YYMV. I appreciate that, and always read multiple sources and do a bit of my own research before buying a product.

    While I appreciate constructive criticism and conflict, the way the last poster did it was just ugh! Basically the last poster has a shitty attitude is what I’m saying.


  12. Hello! Firstly, I love your blog and am so grateful you take the time to share your routine and help demystify the wonderful world of skin care ^.^ it can be so overwhelming for beginners, so thank you!

    I have a few questions and am hoping you can give me some clarity. I am thinking about incorporating an AHA/BHA step to my routine (currently cleansing, toning, moisturizing, and weekly exfoliation through clay mask) I am, however, still struggling with acne and have a suspicion it is due to dead skin cell buildup so I am hoping the chemical exfoliant can remedy this issue. My confusion lies in the idea of using the chemical exfoliant and then not washing the face afterwards. In my mind, once the dead skin has been lifted or broken down my immediate reaction is to want to wash it away and get far away from it as possible!

    Is there something I am missing about the process that makes not washing the face after okay and preferable? Also does applying the chemical exfoliant after a serum not break down or denature the serum as well?

    I know skin care is as unique to each person as the person themselves so what may work wonders for some, may not be the answer for everyone but I am hoping you could give me some insight!

    Thank you!


    1. Hi Rachel! Sorry for the late response! Daily use strength acids (say, 2% salicylic acid BHA or 8% glycolic AHA) work gradually to dissolve the bonds between dead skin cells and allow them to go away faster than they would otherwise, but it isn’t an instantaneous process–generally they’re not going to create a layer of dead gunk on your face the same night you put them on. That’ll be different for peel-strength acids though!


  13. Hi Fiddy. I love, love, love your blog! Very helpful and informative especially for a beginner like me.

    I just started Asian skincare routine about a week and am absolutely satisfied with the result. However I have some concerns with milia seeds on my eyelids and under my eyes. A bit scared about poking them with needles. I’ve read somewhere that AHA acids might help to reduce them. I’m considering COSRX AHA 7 Whitehead Power Liquid.

    Would love to hear some recommendations or points from you.

    Thank you!


  14. hello!! i have few questions… recently i bought the Cosrx Bha Blackhead Power Liquid and the Benton Aloe BHA Skin Toner, both new to my routine, but i did it before reading this post !! so is it ok for my skin to use both bha products at the same time? after using those i will apply the MIZON Snail Repair Intensive Ampoule, The Face Shop Chia Seed No Shine Hydrating Cream and my sunscreen. also, my skin is dry but with blackporesd on the t zone, it’s sensitve as well…


    1. Hi, I don’t think the Benton BHA toner is formulated to exfoliate effectively, so you should be okay, but I would go slowly at first to make sure your skin can indeed tolerate them together.


  15. Hi Fiddy! Thanks for the great post! I have just started using cosrx AHA power liquid and klairs vitamin C. I use vitamin C morning and night, AHA only at night. However AHA makes my skin so flakey the next day! I use 50 SPF (pa++++) every morning. What should I do to combat flakiness? It looks so bad under make up!


  16. Hi! 🙂
    I have combination skin (dry in cheeks, oily in T-zone, have whiteheads and blackheads on nose) so which acid toner will be best for my combination skin? AHA or BHA?


  17. I heard that aha and bha is not recomended to used together. Because both of them is a chemical exfoliants. Our face can be iritated and become sensitive. And also, don’t use a vitamin c serum when you are using aha or bha, because vitamin c is also exfoliate our face. For further information you can ask a dermatologist if you want 🙂


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