AHA/BHA toner: Cosrx or Anua, and how to use it

The K-beauty question we hear most is about acid toners: “Cosrx or Anua?” Here is our honest answer: what AHA and BHA do, which toner suits which skin, what not to mix it with, and why one of Anua's best-known toners does not exfoliate at all.

What an exfoliating toner does

Skin renews itself all the time, but dead cells cling to the surface: skin looks rough and dull, and pores clog. A scrub removes them by friction; an acid toner dissolves the bonds that hold them together. That is chemical exfoliation. A toner stays on the skin and keeps working, so frequency and sun protection matter.

AHA, BHA and PHA in plain words

• AHAs are water-soluble acids, most often glycolic and lactic acid. They work on the surface: smoother texture, a fresher-looking tone. Worth knowing: AHAs make skin more sensitive to the sun.
• BHA is salicylic acid and its derivatives. It is oil-soluble, so it mixes with sebum and gets into pores. The pick for oily skin, blackheads and congested pores.
• PHAs (gluconolactone, lactobionic acid) are a newer generation of AHAs: they exfoliate similarly but sting less and help hold moisture, so they are often chosen for sensitive skin.

In our shop, AHA plus BHA in one bottle means Cosrx; BHA alone means Anua. We have no PHA toner right now. Anua's Heartleaf 77 Clear Pad contains PHA, but we do not sell it, and it is easy to confuse with the Heartleaf toner below.

Cosrx AHA/BHA Clarifying Treatment Toner: a gentle start

It contains glycolic acid (AHA), betaine salicylate (BHA), willow bark water and apple fruit water, plus panthenol and allantoin. Cosrx aims it at people new to chemical exfoliation: gentle exfoliation, daily use, all skin types including sensitive. Cosrx does not publish acid percentages, and we will not guess.

How to use it, per Cosrx: after cleansing, put the toner on a cotton pad and wipe over the face, avoiding the eyes and mouth. If you use it during the day, follow with a broad-spectrum sunscreen of SPF 30 or higher. Cosrx also warns not to use it with other acids, retinol or vitamin C, and to avoid it during pregnancy and breastfeeding.

Cosrx AHA/BHA Clarifying Treatment Toner — toner — 16,75 €

This toner is not for you if you already use retinol or another acid, or if your skin is irritated or sunburnt right now. And if pores and blackheads are your main issue, look at Anua's 2% BHA toner.

Anua BHA 2% Gentle Exfoliating Toner: for pores and oily skin

One acid here: salicylic acid, 2% according to Anua. Anua says it exfoliates dead skin cells to clear pores, panthenol and six ceramides help maintain the skin's moisture barrier, and tea tree leaf extract and hyaluronic acid soothe and calm. It is fragrance-free.

Anua is direct about frequency: once every 2–3 days, watching how your skin responds. Apply with hands or a cotton pad to face and neck; in the morning, only with SPF 30 or higher.

Anua BHA 2% Gentle Exfoliating Toner — toner — 21,39 €

This toner is not for you if your skin is dry and flaky with no congested pores or blackheads: that is exactly what BHA is for. And never use it on the same evening as the Cosrx toner.

Anua Heartleaf 77 is not an exfoliant

We checked the ingredient list on Anua's own site: there is no AHA, BHA or PHA in it. It is a soothing toner made with 77% heartleaf (Houttuynia cordata) and hyaluronic acid, which Anua says is designed to calm irritation and moisturise, morning and night. It will not clear pores, but it suits the days you skip acids and skin that does not tolerate them yet.

Anua Heartleaf 77% Soothing Toner — toner — 6,99 €

Which toner for which skin

• Oily skin, blackheads, visible pores: Anua BHA 2%, starting with two evenings a week.
• Combination skin (oily T-zone, normal cheeks): Cosrx AHA/BHA on the whole face, or BHA on the T-zone only.
• Sensitive skin: start with Heartleaf 77. If you want acids, try Cosrx, rarely and only after a patch test.
• Dry skin: acids no more than a couple of times a week, always followed by a moisturiser.

Rules of thumb, not laws: if your skin reacts differently, trust your skin.

How often, and in what order

Even if the maker allows daily use, start with 2–3 evenings a week and go up only if there is no redness or tightness. The American Academy of Dermatology puts the principle simply: the more aggressive the exfoliation, the less often it needs to be done.

1. Cleanse.
2. Acid toner on a cotton pad, no rubbing; let it dry.
3. Moisturiser.
4. In the morning, sunscreen as the last layer.

Moisturiser after an acid is not a formality: exfoliating dries the skin, and dermatologists advise moisturising straight afterwards. Cosrx describes its cream with 92% snail secretion filtrate as suited to freshly exfoliated skin.

Cosrx Advanced Snail 92 All in One Cream — face cream — 22,99 €

What not to combine

• Two acid toners in one routine: pick one.
• Retinol, retinoids and benzoyl peroxide: they already make skin more sensitive. Cosrx adds vitamin C.
• A face scrub on the same day.
• Sunburnt skin, cuts or open wounds: no acids on those days.

If you use prescription skin treatments, ask your doctor first.

SPF, the next day too

The US Food and Drug Administration (FDA) notes that AHAs increase the skin's sensitivity to UV, and advises sun protection for as long as you use them and for a week afterwards. So the morning after an evening acid starts with SPF, even on a grey Tallinn day. Both makers also ask for SPF 30 or higher when the toner is used by day.

We stock Cosrx Aloe Soothing Sun Cream SPF50+/PA+++: a light cream you apply generously 30 minutes before sun exposure and reapply during the day. It contains fragrance, so if your skin reacts to fragrance, patch test it first.

Cosrx Aloe Sun Cream — cream — 15,49 €

Patch test, and when to stop

The American Academy of Dermatology suggests testing a new product like this: apply it twice a day for 7–10 days to a coin-sized spot on the underside of your arm or the bend of your elbow. If you get redness, itching or swelling, wash it off and do not use it again.

Over-exfoliation looks similar: redness, tightness, and even your usual moisturiser stings. Pause the acids and keep a gentle cleanser, moisturiser and SPF. If the irritation does not settle, see a dermatologist.

Not sure which toner to pick? Come and see us at Mardi 1 in Tallinn and we will help. All face care is in Face care, with Cosrx and Anua on their own pages.