COSRX BHA vs. AHA: Which Chemical Exfoliator Is Right for Your Skin?
By KSkinBio Editors · Updated 2026
COSRX makes two of the most beloved chemical exfoliators in K-beauty: the BHA Blackhead Power Liquid and the AHA 7 Whitehead Power Liquid. They’re often sold as a set. But using the wrong one for your skin concerns doesn’t just waste product — it can cause real irritation. Here’s exactly what each one does and which one you need.
BHA (Beta Hydroxy Acid): The Pore Specialist
COSRX’s BHA uses betaine salicylate — a gentler version of classic salicylic acid — derived from willow bark. BHA is oil-soluble, meaning it can actually penetrate inside the pore to dissolve the sebum and dead cell buildup that cause blackheads, whiteheads, and acne. AHA simply cannot do this — it can only work on the skin’s surface.
This is the product for: clogged pores, blackheads, acne-prone skin, excess sebum, and oily skin. Use it 2–3 times per week on areas where you have visible congestion (usually the nose, chin, and forehead T-zone).
COSRX BHA Blackhead Power Liquid
Betaine salicylate exfoliant that penetrates pores to clear blackheads, reduce congestion, and control sebum. Gentler than pure salicylic acid.
AHA (Alpha Hydroxy Acid): The Surface Resurfacer
COSRX’s AHA 7 uses glycolic acid at 7% concentration. AHA is water-soluble and works on the skin’s surface, dissolving the "glue" that holds dead skin cells together and causing them to shed more rapidly. The result: brighter skin, smoother texture, reduced fine lines, and fewer surface-level clogged pores (milia, whiteheads at the surface).
AHA is for: dull skin, rough texture, fine lines, surface pigmentation, and whiteheads. It’s not the right tool for deep blackheads — that’s BHA territory. Use it 1–2 times per week at night, always followed by SPF the next morning (AHA increases photosensitivity).
COSRX AHA 7 Whitehead Power Liquid
7% glycolic acid with apple water to resurface skin, smooth texture, and fade surface pigmentation. Use at night, always follow with SPF.
Can You Use Both? How to Alternate
Yes — but never on the same night. Layering two chemical exfoliants simultaneously more than doubles the irritation potential. Here’s a sustainable alternating schedule:
- Monday: BHA
- Wednesday: AHA
- Friday: BHA
- Remaining nights: No exfoliant — let your barrier recover
If you experience redness, tightness, or flaking: reduce to once a week for each and increase usage only when your skin has adjusted. Exfoliation tolerance is built over weeks, not days.
FAQ
Do I need to pH-prime my skin before using COSRX exfoliants?
Not necessarily. Both COSRX exfoliants are formulated at the correct pH (around 3.5–4.0) and are effective without pH-priming steps. Apply them on clean skin after a low-pH toner, wait 20 minutes before applying other products.
Can I use COSRX BHA or AHA with retinol?
Use them on separate nights. Both exfoliants and retinol increase skin cell turnover — combining them causes cumulative irritation. Alternate exfoliant nights with retinol nights.
Can sensitive skin use BHA or AHA?
Start slowly — once per week, rinsed off after 10 minutes rather than left on. COSRX’s betaine salicylate is gentler than pure salicylic acid, making the BHA better tolerated by most sensitive skin types than the AHA.