K-Beauty Guides
AHA vs BHA vs PHA: Korean Exfoliants Explained
Korean exfoliants mostly rely on three families of acids: AHAs for dullness and rough texture, BHAs for oily skin and clogged pores, and PHAs for sensitive skin that cannot tolerate stronger acids. The Korean approach favours gentle, frequent-enough exfoliation over harsh peels, usually in a toner, pad or light serum. This guide explains the difference between AHA, BHA and PHA, how to choose one and how to use it safely.
Why exfoliate at all?
Skin naturally sheds dead cells, but the process slows with age, dryness, sun damage and cold weather. When old cells build up, skin can look dull, feel rough and absorb moisturizers less evenly. Pores can also fill with a mix of oil and dead cells, which shows up as blackheads, whiteheads or a bumpy texture.
Chemical exfoliants loosen the bonds between dead cells so they shed more evenly. Compared with gritty scrubs, they are usually more uniform and less likely to cause micro-tears when used correctly. Korean brands have built entire product lines around this idea, from daily toner pads to weekly treatments.
AHA vs BHA vs PHA: the key differences
| Exfoliant | Common examples | Dissolves in | Best for | Watch out for |
|---|---|---|---|---|
| AHA (alpha hydroxy acid) | Glycolic, lactic, mandelic acid | Water | Dullness, rough texture, uneven tone, dry or normal skin | Stinging, increased sun sensitivity |
| BHA (beta hydroxy acid) | Salicylic acid, betaine salicylate | Oil | Oily skin, blackheads, clogged pores, breakouts | Dryness; avoid if allergic to aspirin-type salicylates |
| PHA (polyhydroxy acid) | Gluconolactone, lactobionic acid | Water | Sensitive, reactive or dry skin, beginners | Slower, subtler results |
| LHA (lipo hydroxy acid) | Capryloyl salicylic acid | Oil | Oily or sensitive skin wanting gentle pore care | Less common, still an acid |
AHAs in more detail
Glycolic acid has the smallest molecule and works fastest, but it is also the most likely to sting. Lactic acid is gentler and adds some hydration, which makes it popular for dry skin in winter. Mandelic acid has a larger molecule that works slowly and is often chosen for sensitive or darker skin tones prone to irritation-related marks.
BHAs in more detail
Because salicylic acid dissolves in oil, it can work inside the pore lining where sebum builds up. Many Korean brands use betaine salicylate, a gentler salicylic derivative, in toners and liquids. Products such as COSRX BHA Blackhead Power Liquid and ANUA BHA 2% Gentle Exfoliating Toner are well-known Korean examples aimed at pores and texture.
PHAs in more detail
PHAs have large molecules that stay closer to the surface, which makes them less irritating. They also attract water, so they exfoliate while helping hydration. PHA toners are a good first step for anyone who has reacted to AHAs before.
How to choose the right exfoliant for your skin
- Oily skin with blackheads: start with a BHA toner or liquid. Our guide to Korean skincare for oily skin and large pores builds a full routine around it.
- Dry, dull or rough skin: try lactic acid or a PHA, followed by a rich moisturizer.
- Sensitive or rosacea-prone skin: choose PHA or a very gentle LHA, and introduce it slowly. Speak to a dermatologist if you have diagnosed rosacea or eczema.
- Combination skin: use BHA on the T-zone and a milder PHA on the cheeks, or alternate days.
- Uneven tone and texture: AHAs help, but sunscreen matters even more.
Toners, pads, serums or peels?
The format affects how strong an exfoliant feels as much as the acid itself.
- Exfoliating toners are usually leave-on and lightweight. They are easy to apply to the whole face or just the T-zone.
- Toner pads, such as ANUA Heartleaf 77 Clear Pad or Medicube Zero Pore Pad, are pre-soaked and convenient. Use light pressure; rubbing adds friction.
- Serums and liquids can be more concentrated. Apply a thin layer once you know your skin tolerates the acid.
- Wash-off peels and peeling gels stay on for a short time and are rinsed off, which some people find easier to control.
- Spicule and physical-chemical hybrids work differently again; see our guide to how often to use Dr. Melaxin Peel Shot for a weekly schedule example.
How to introduce a chemical exfoliant safely
- Patch test on the jawline or behind the ear for a few days.
- Start two evenings a week on clean, dry skin.
- Wait a few minutes before applying hydrating toner and moisturizer.
- Increase slowly to every other night if your skin stays calm for two or three weeks.
- Do not stack exfoliants: one acid product per routine is plenty for most people.
- Pause retinoids on exfoliation nights, or alternate them. Our Korean retinol guide explains how to schedule both.
- Wear sunscreen every morning, because AHAs in particular can increase sun sensitivity.
Signs you are over-exfoliating
More is not better. Stop all acids for a week or two and focus on gentle cleansing, hydration and a soothing moisturizer if you notice:
- Stinging when you apply plain moisturizer or water.
- A tight, shiny or “plastic” look to the skin.
- New redness, flaking or a rash-like texture.
- More breakouts than usual, especially small, itchy bumps.
- Products that never bothered you suddenly burning.
These are typical signs of a stressed skin barrier. If irritation persists, swelling appears or you suspect an allergic reaction, stop the product and see a pharmacist, doctor or dermatologist.
Exfoliating in winter
Cold air outside and dry indoor heating mean many people need to exfoliate less often between November and March. Switch from glycolic acid to lactic acid or PHA, cut back to once or twice a week, and pair exfoliation nights with a richer cream. Exfoliation can also help moisturizers sink in better on flaky patches, so the goal is balance, not stopping entirely.
A simple winter schedule might look like this: a PHA or lactic acid toner on Monday and Thursday evenings, a hydrating sheet mask on Saturday, and gentle cleansing with a barrier cream on every other night. If your lips and the corners of your nose get chapped, keep acids away from those areas altogether. When the weather warms up in spring and your skin feels oilier, you can return gradually to your usual exfoliation rhythm.
FAQ: Korean exfoliants
Can I use AHA and BHA together?
Some combination products, such as COSRX AHA/BHA Clarifying Treatment Toner, are formulated to include both at gentle levels. Combining two separate strong products is more likely to irritate; alternate them instead.
Should I use an exfoliating toner every day?
Only if the product is designed for daily use and your skin tolerates it. Many people get better results with two to four times a week.
Do I still need a hydrating toner?
Yes. After an exfoliating step, a hydrating toner or essence helps calm the skin. See our list of the best Korean toners for both types.
Is BHA safe during pregnancy?
Advice on salicylic acid during pregnancy varies with strength and product type. Ask your doctor or pharmacist before using any acid exfoliant while pregnant or breastfeeding.
Can exfoliants remove dark spots?
Regular exfoliation can make skin tone look more even over time, but persistent pigmentation often needs targeted ingredients, sun protection and sometimes professional advice.
This guide is general information and not medical advice. For an ingredient-by-ingredient approach to your routine, explore our Korean skincare routines.