What is the difference between AHA, BHA and PHA?

AHAs (alpha-hydroxy acids) are water-soluble acids that work on the skin surface, loosening the bonds between dead skin cells so they shed more easily. Common AHAs include lactic acid, glycolic acid and mandelic acid. BHAs (beta-hydroxy acids) — the main one in skincare being salicylic acid — are oil-soluble, which means they can penetrate into pores through oil and sebum. This makes BHA particularly effective for oily, congested and acne-prone skin. PHAs (polyhydroxy acids) such as gluconolactone and lactobionic acid are larger-molecule acids that work more slowly on the surface — making them gentler and better-tolerated by sensitive skin.

How often should I exfoliate?

Most skincare professionals and dermatologists recommend starting with 1-2 times per week for chemical exfoliants and assessing how your skin responds before increasing frequency. Some people with resilient oily skin may tolerate 3x per week; sensitive skin may only tolerate once every 1-2 weeks. Physical exfoliants (scrubs) should be used more sparingly and gently. There is no single universal frequency — pay attention to how your skin responds, and reduce frequency if any signs of irritation or barrier disruption appear.

What are the signs of over-exfoliation?

Over-exfoliation is one of the most common causes of barrier damage. Signs include: skin that stings or burns when normally-tolerated products are applied; unusual tightness or dryness that persists despite moisturising; increased redness, sensitivity or flushing; a shiny, tight feeling rather than a healthy glow; and breakouts appearing in areas not typically prone. If you notice these signs, stop all exfoliants immediately and focus on barrier repair for at least 2-4 weeks.

Can I use AHA and BHA together?

Using both AHA and BHA at the same time, in the same routine session, is generally not recommended — particularly for beginners or sensitive skin. Together, they significantly increase the risk of barrier disruption and irritation. A more sustainable approach is to alternate: use AHA on some nights and BHA on others, or use a combined product formulated specifically to balance the two acids. Never use chemical exfoliants on the same night as retinoids.

Do Korean exfoliators work differently from Western ones?

The active exfoliating ingredients (AHAs, BHAs, PHAs) are the same in both Korean and Western formulations. What differs is sometimes the approach and format: Korean exfoliating toners are a popular format — a toner-consistency liquid applied with cotton pad or patted in, rather than a separate mask or thick cream. These feel gentler in format and are easy to incorporate into a layered routine. Many Korean exfoliators are also formulated alongside calming ingredients (centella, niacinamide) to balance the potentially irritating acid step.

Product Guide

Korean Exfoliators

Exfoliation — the removal of dead skin cells from the surface — is a beneficial step in most skincare routines when done correctly. Korean skincare tends to favour chemical exfoliation over physical scrubs, using acids that work gently and precisely at a cellular level rather than relying on abrasive friction.

This guide explains the different types of chemical exfoliants found in Korean skincare, how to use them safely, how often to exfoliate, and the important warning signs of over-exfoliation.

General Information Only. This page provides educational skincare information and is not medical advice. If you have persistent acne, eczema, rosacea, allergies, skin irritation, pigmentation changes or any medical skin condition, please consult a qualified dermatologist or healthcare professional before changing your skincare routine. Individual results vary. Always patch test new products.

Caution: Those with aspirin allergy or salicylate sensitivity should avoid salicylic acid (BHA). Those who are pregnant should check with a healthcare professional before using any acid exfoliants. Do not use on broken or sunburned skin. Always patch test new exfoliants before full-face use.

Chemical vs physical exfoliation

Chemical exfoliation

Uses acids (AHAs, BHAs, PHAs) to dissolve the bonds between dead skin cells, allowing them to shed naturally. Works without physical friction. More predictable and less likely to cause micro-tearing.

Preferred in Korean skincare

Physical exfoliation

Uses abrasive particles (sugar, rice bran, microbeads) or tools to mechanically remove dead cells. Effective when used gently, but requires care — aggressive scrubbing can cause micro-tears and barrier damage.

Use sparingly and gently if at all

AHA, BHA and PHA compared

AHAs — Alpha-Hydroxy Acids

Examples: Lactic acid, glycolic acid, mandelic acid

Best for: Dry, dull, uneven tone, mature skin; surface texture improvement

How it works: Water-soluble; work on the skin surface to loosen dead cell bonds

Caution: Increase sun sensitivity — always wear SPF when using AHAs

BHA — Beta-Hydroxy Acid

Examples: Salicylic acid (0.5–2%)

Best for: Oily, acne-prone, congested, blackhead-prone skin

How it works: Oil-soluble; penetrates through sebum into pores to clear congestion

Caution: Avoid with aspirin allergy; not for pregnancy; can be drying if overused

PHAs — Polyhydroxy Acids

Examples: Gluconolactone, lactobionic acid

Best for: Sensitive skin, those new to chemical exfoliation, redness-prone skin

How it works: Larger molecules than AHAs — work more slowly on the surface

Caution: Gentler than AHAs/BHAs but still worth patch testing

How to incorporate exfoliation safely

Start with once a week and assess your skin's response before increasing frequency.

Use exfoliants in the evening — AHAs temporarily increase sun sensitivity.

Always follow with moisturiser and SPF the following morning.

Do not use on the same evening as retinoids.

Do not combine AHA and BHA in the same session — alternate nights instead.

Patch test any new exfoliant on a small area (inner arm or behind the ear) before full-face use.

Stop immediately and focus on barrier repair if you notice signs of over-exfoliation.

Signs of over-exfoliation — stop and repair

Stinging or burning when applying products that were previously tolerated
Unusual tightness or dryness despite moisturising
Increased redness, sensitivity or flushing
A shiny, tight, almost raw-feeling complexion
New breakouts in areas not normally prone

If these signs appear, stop all exfoliation immediately. Focus on gentle cleansing, ceramide moisturiser and no actives for 2-4 weeks.