How to use AHA/BHA • K-Beauty Ingredient Spotlight

Let’s continue The Korean Beauty for Beginners series with detailed posts on your favorite ingredients. Today we will cover the two ingredients that we get the most questions about AHA & BHA.

Physical VS. Chemical exfoliators

Both AHA & BHA are so-called chemical exfoliants. Chemical exfoliators gently slough off dead skin cells with active ingredients such as Salicylic or Lactic acid. Physical exfoliating products include scrubs, exfoliating mitts, and cleansers, that often contain small particles that create friction to help exfoliate the skin. Friction can cause irritation or micro-tears on the skin, making it less suitable for those with acne-prone or sensitive skin. A big difference between these two is the frequency of use. You would use a scrub once a week and see results instantly, but you might be damaging your skin at the same time. The frequency of using chemical exfoliants completely depends on the percentage you are using. View the table below for a suggestion on how to use these popular Korean AHA and BHA products.

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How to use the AHA BHA Clarifying Treatment Toner

Can be used daily after cleansing. Spray directly onto (dry) skin or use a cotton pad to swipe the toner over the face. Also a great option for body acne!


How to use the BHA Blackhead Power Liquid

Can be used multiple times a week. Apply to the whole face after cleansing or after using a pH adjusting toner. Start slowly by using once a week then increase frequency when necessary.


How to use the Clear Skin 8% AHA Essence

Use once or twice a week after cleansing on dry skin. Preferably wait 30 minutes afterward before applying any other skincare. If you feel too much sensation when using it for the first time, rinse off after 10 minutes.

What is AHA?

Alpha Hydroxy Acid is a water-soluble chemical exfoliant that treats dry, dull, and patchy skin. AHA dissolves the binding material that holds together dead skin cells, making room for new skin cells to reach the surface of the skin. When you have too much dead skin, it can be hard for skincare products to penetrate and be effective. 

What are the benefits of AHA?

New skin cells make your skin appear brighter, less dull, and even out the complexion. Clear skin aside, AHA is known to thicken the epidermis (upper skin layer) and increases the collagen production. Some types of AHA such as Lactic acid can also help with redness. 

Different types of AHA

Glycolic Acid is the most popular and common AHA because of its small molecular size. Because of its small size, it easily and effectively penetrates the skin. The downside is, it can also easily irritate your skin if you use it too much. Start with a lower percentage once a week. You can also rinse it off after a few minutes to get used to the product. 

Lactic Acid,derived from milk, works great for tackling redness. Those with Rosacea or sensitive skin will benefit the most from this AHA. Its molecular size is bigger than the size of Glycolic Acid, but not as big as with Mandelic Acid.

Mandelic Acid has anti-bacterial and anti-microbial properties, making it great for those with acne-prone skin. Because it’s molecular size is the biggest of all of these AHA’s it takes longer to get into action but it makes it less irritating.

What is BHA?

Beta Hydroxy Acid is a popular acid for solving pore-related issues. It is most effective for acne-prone and oily skin types since it’s an oil-soluble active. BHA deeply sinks into the pores to remove excess oils and dirt, and clean out the pores. 

Salicylic Acid

Salicylic Acid is known for its anti-inflammatory properties, making it great for calming angry skin. Salicylic acid has all the great benefits of AHA, including brightening, firming, and increasing collagen production. However, Salicylic Acid doesn’t posses any humectant ingredients like AHA. Those with dry skin should be a little more cautious using salicylic acid and follow up with hydrating products to prevent the skin from drying out.

Can I combine AHA & BHA?

Unless you are a skincare pro, we recommend staying with one active at a time. Because acids can cause photosensitivity, we recommend using them at nighttime only. Follow up with sunscreen every morning to protect your skin and prevent pigmentation. Slowly introduce new acids into your skincare and preferably alternate AHA, BHA, and other acids like vitamin C in different routines. For those with oily skin, combining AHA and BHA might be beneficial, some products even contain both ingredients in one! Those with sensitive or dry skin should proceed with caution, minimizing irritation and drying of the skin. 


Hope this was helpful!

Love, Ichigo

23 thoughts on “How to use AHA/BHA • K-Beauty Ingredient Spotlight

  1. Anonymous says:

    Hi! I’ve been using BHA and AHA for a while and neither ever caused me irritation before. But the last couple weeks, both irritated my skin. The only thing that changed in my skincare routine is my cleanser. The one i have now does have some irritants in it. What cleansers would you recommend to use in a routine with CosrX 7% AHA and CosrX 4% BHA. Would the CosrX low ph gel cleanser work?

    • says:

      Hi Mathilde, I would not suggest the Cosrx Low pH Good Morning Gel cleanser as that also has salicylic acid in it. You might want to add a moisturizing cleanser in your routine because of your chemical exfoliation. Our personal favorites are the Pure Heals Propolis Foam Cleanser or the Etude House Soon Jung Whip Cleanser 😀

  2. Anonymous says:

    Hello! I just recently discovered your blog and I love how informative they are! I used to think that I have a clear understanding on the correct layering of the skincare products that I have but after reading your blog, I’m now a bit baffled. Lol! These are the products I currently have and how I layer them. Please help me check if I’m indeed doing it correctly or not.

    1. I just wash my face thoroughly with water in the morning
    2. COSRX One Step Original Clear Pads
    3. Klairs Freshly Juiced Drop Vitamin C
    4. COSRX Natural BHA Skin Returning A-sol (for spot treatment only; normally in T-Zone area)
    5. COSRX Galactomyces 95 Whitening Power Essence
    6. Mizon Skin Recovery Gel Cream (or other moisturizer that I’m trying out)
    7. Biore UV Aqua Rich Watery Essence SPF50+

    1. Etude house O-LE-MONG Sherbet Cleanser (used only at night time to remove make up & sunscreen)
    2. Hada Labo Whitening Face Wash
    ** I sometimes use Garnier Micellar Water only at night if I’m too tired to do double cleansing.
    3. COSRX One Step Original Clear Pads
    4. COSRX BHA Blackhead Power Liquid (used on alternate days with #5)
    5. COSRX AHA Whitehead Power Liquid (used on alternate days with #4)
    6. COSRX Natural BHA Skin Returning A-sol (for spot treatment only; normally in T-Zone area)
    7. COSRX Galactomyces 95 Whitening Power Essence
    8. Mizon Skin Recovery Gel Cream (or other moisturizer that I’m trying out)
    9. Laneige Water Sleeping Mask (2-3x a week) or 10. Face Mask

    ** I also use Aztec Secret Indian Healing Clay mask once a week after double cleansing. I go straight to #7 PM routine if I do so.

    Btw, is it safe to use A-sol for the whole face and not just as spot treatment? I know my comment is lengthy but I hope you can find time to respond. Thanks!

    • says:

      Hello Lainey, Thank you for dropping by on here! You’ve got a pretty set routine there and seem to understand the layering well no worries! From your post I can’t really tell what your skin type or your skincare goals are however based on the acids the routine looks good but maybe a bit drying? The only two suggestions I would make is adding more moisture and skipping the Cosrx pads in the morning. These pads also contain BHA so I would refrain from using them in the morning and just go straight to the Vitamin C or use a more hydrating toner beforehand like the Etude House Soon Jung Toner. Also, waiting 20 min after applying the vitamin C before applying any other skin care item is the way to go, same for the acids in the evening routine. Please let us know if you have any other questions 😀

      ‘xo Ichigo

  3. Anonymous says:

    I’m 20 years old. i want to use product that match my age so, what’s products that i can use.
    I read the detail of each product. some product for 40s 30s so I am afraid that i use the wrong product that I am just 20s and it do’t match my skin type. if i use all this i think my skin will get older

    • says:

      Hi there, It’s not so much a matter of which product matches your age but more so which matters your skin type and concerns. Hope that helps 🙂

  4. Anonymous says:

    Hi there!
    This post says to put aha/bha after toner, or as a toner, but if that’s the case why are there bha/aha serums? Isn’t putting on the serum at night and then letting the serum do its magic while you sleep also an option?

    • says:

      Hi Lydia, there are a variety of different type of products with actives like AHA & BHA including toners, serums and even creams. It’s best to apply these actives to directly to the skin after balancing its pH level. For example you can also use an hydrating/ balancing toner and use your serum with actives after that. Just make sure that you take note of the ingredients of the other products you are using and check if they aren’t in conflict with the actives you are using.

  5. Anonymous says:

    Hi there,
    Thanks for such n informative write up on usage of acids.. I have never used any acids products in my skincare routine before, my skin its generally clear excpt the t zone n cheeks area which I have a problem with on visible pores, whiteheads n blackheads.

    Can you recommend which or the type acids I should try to incorporate into my routine , something mild yet effective.

  6. Anonymous says:

    And the sequence of acid application its after say our regular hydrating toner , then acid say the Eg.Corsxr bha then let it seat on for 20 mins, then continue on to the next step of essence/serum, moisturiser it’s that right ?

    Thank so much, would be looking forward to your advice.

  7. Anonymous says:

    Hi! Is it still necessary to use a chemical peeling gel for exfoliation once/twice a week if you use an essence/serum with AHA + BHA in your evening skincare routine?

    • says:

      Hi Mia, if you are properly using your AHA/BHA already there should be no need for an additional peeling gel as both AHA and BHA are already chemical exfoliants 🙂

      • Anonymous says:

        Hello, I have a question about AHA and vitamin C. I have an AHA toner and vitamin C serum. Is it okay if I first use cleanser and go directly to the vitamin C skipping the AHA toner for morning routine? Can I use cleanser, then AHA toner and then the vitamin C serum for the evening routine?

        • says:

          Hi Alice, thank you for your comment! I think it depends a lot on the products you are using. Vitamin C and AHA can be combined in the same routine if the percentages are not too high and the skin is used to acids, however, to prevent irritation and to have the most benefits of the actives you are using I would use them separately. Also, vitamin C once a day is more than sufficient.

  8. Anonymous says:

    I m using vitamin c serum in my morning routine and aha/bha in the evening routine. I m a little confused with niacinamide, i m using secret key first treatment essence is it ok to use it after vitamin c in the morning and after aha/bha in the evening?

  9. Anonymous says:

    Hi, thanks for this informative post. I recently bought the Pyukang Essence and the Cosrx Whitehead AHA and would like to ask on how i can add to to my routine that includes a Retin A 0.05% that I’m currently using every 4th or 5th night as i just started out. I have very sensitive, dehydrated acne prone dry skin.

    Here’s my current routine:

    Wash my face with the Cetaphil gentle cleanser, spritz my face with Avene thermal water, use the Vichy 89 Mineral water, apply the Avene Tolerance Extreme and lastly use the La Roche Posay Ultra Sunscreen.

    Cleans my skin with the Bioderma H2O micellar water then the Avene tolerance extreme clensing lotion and wipe that off with a towel. Spritz my face with Avene thermal water, use the Vichy 89 Mineral water, apply the Avene Tolerance Extreme, wait for 30min, then apply my Retin – A every 4th night.

  10. Anonymous says:

    Hi, can i ask if it is safe to use an aha/bha toner as substitute to water to mix with bentonite clay mask?

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