AHA, BHA and PHA exfoliants: which one for your skin, and how often

Chemical exfoliation has replaced grainy scrubs in most Korean routines, and for good reason: it is more consistent, gentler and better targeted. But between AHA, BHA and PHA, pads, serums and ampoules, it is easy to pick the wrong product or the wrong frequency, and end up with a damaged skin barrier. Here is how these three families of acids work, which one matches your skin, and how often to use it.

Why exfoliate, and why chemically?

The epidermis renews itself in about four weeks, longer with age. When dead cells build up on the surface, skin looks dull, texture becomes uneven and pores clog. A chemical exfoliant dissolves the bonds holding those cells in place, without rubbing. Unlike mechanical scrubs, it works evenly and does not nick the skin's surface.

Korean skincare has taken this logic further than most: low concentrations, practical formats (soaked pads, daily serums) and formulas that pair the acid with soothing agents. The goal is not a dramatic "peel", but light, regular exfoliation.

AHA, BHA, PHA: the three families explained

AHA: the surface exfoliant

Alpha hydroxy acids (glycolic, lactic, mandelic) are water-soluble and work on the surface of the epidermis. They smooth texture, restore radiance, fade superficial dark spots and soften fine lines. Their intensity depends on molecule size: glycolic acid, the smallest, penetrates quickly and irritates more; mandelic acid, the largest, is the gentlest. AHAs are photosensitising: sunscreen the next day is essential.

BHA: the pore exfoliant

Beta hydroxy acid is salicylic acid. It is oil-soluble, so it can pass through sebum and clean inside the pore. This is the acid for blackheads, comedones and combination to oily skin. It also has an anti-inflammatory action, useful for blemish-prone skin. In Europe, cosmetics cap it at 2%, and Korean formulas often sit well below that.

PHA: the sensitive-skin exfoliant

Polyhydroxy acids (gluconolactone, lactobionic acid) are larger molecules that penetrate less and exfoliate more gently. They also have a hydrating and antioxidant effect. A twelve-week study showed no loss of effectiveness on signs of ageing compared with a classic AHA, with less irritation. This is the entry point for reactive skin, mild rosacea and anyone who has never tolerated acids.

Which AHA BHA PHA exfoliant for your skin?

• Combination to oily skin, visible pores, blackheads: BHA first, possibly combined with a PHA or a gentle AHA. The Medicube Zero Pore Pad pairs BHA and PHA on a double-sided pad: the textured side exfoliates, the smooth side polishes. The pad format is practical and well dosed for regular use.
• Normal skin with uneven texture: a low-dose AHA + BHA combination. The Zero Pore Pad 2.0 pairs lactic acid and BHA with panthenol, for surface smoothing with less tightness.
• Skin that wants a very gentle daily exfoliant: the numbuzin No.3 Skin Softening Serum is a serum, not a pad: a low-concentration AHA, BHA and PHA complex in a milky texture that does not sting. It slips into the evening routine, up to daily if the skin tolerates it.
• Dull skin, first signs of ageing: an AHA/BHA used as a course. The Dr.Melaxin Peel Shot Ampoule is more concentrated than a serum, to be used two or three evenings a week, alternating with soothing evenings.
• Sensitive or reactive skin: PHA alone, once a week to start. If even PHA causes redness, the skin does not need an exfoliant for now; focus on the barrier with our sensitive skin selection.

All our references are gathered in the AHA/BHA/PHA exfoliants collection, along with our targeted products for acne and pores.

How often should you exfoliate?

This is the question that matters most, and the one people get wrong most often. The right rhythm depends on the product and the skin, but a few guidelines apply to everyone.

• To start: once or twice a week, in the evening, for two weeks. Watch for: no persistent redness, no tightness the next day, no "thin skin" feeling.
• At cruising speed: two to three times a week for a pad or an ampoule; up to every evening for a very gentle serum like the numbuzin No.3, if the skin tolerates it.
• The warning sign: skin that shines oddly, reddens at everything, stings on contact with water. That is a skin barrier damaged by over-exfoliation. Stop all exfoliants for two to four weeks and hydrate with ceramides.

Skin does not need daily exfoliation to be clear. A twice-weekly rhythm kept up for months gives better results than daily exfoliation abandoned after three weeks because the skin reacts.

The mistakes that damage the skin barrier

• Stacking acids. An AHA/BHA pad, then an exfoliating serum, then an acid toner: three exfoliants in one evening. One exfoliating product per evening is enough.
• Exfoliating and applying retinol on the same evening. Both stimulate renewal; together, they irritate. Alternate evenings.
• Exfoliating damaged skin. Sunburn, eczema, persistent redness, peeling skin: wait for the skin to recover.
• Forgetting sunscreen. AHAs increase UV sensitivity for several days. Without SPF the next day, you trade radiance for dark spots. Our guide to Korean sunscreen helps you choose one you will enjoy wearing daily.
• Judging by sensation. An exfoliant that stings hard is not more effective; it is too strong for you. A light tingle for a few seconds is acceptable, burning is not.

How to fit an exfoliant into your evening routine

After cleansing, on dry skin, apply the exfoliant (pad, serum or ampoule), avoiding the eye contour and lips. Wait a minute, then follow with a soothing serum (centella, niacinamide), and finish with a moisturiser, richer than usual on exfoliation evenings. On the following evenings, keep the routine to hydrating and soothing products. In the morning, sunscreen.

Allow two to four weeks for smoother texture and a brighter complexion, eight to twelve weeks for a visible effect on pores and superficial dark spots.

FAQ: AHA, BHA and PHA exfoliants

Can you use AHA and BHA together?

Yes, in a single formula designed for it (like combined pads) or on alternating evenings. What you should avoid is layering several separate exfoliating products on the same evening.

Are chemical exfoliants suitable for sensitive skin?

Yes, provided you choose a PHA or a gentle AHA (mandelic, low-dose lactic), once a week, and listen to your skin. Low-concentration BHA is also well tolerated by many reactive, blemish-prone skins.

Do you need to rinse off an exfoliating pad?

No, Korean pads are designed to be left on the skin, like a toner. Rinse only if a burning sensation appears.

Chemical exfoliant or grainy scrub?

The chemical exfoliant is more consistent and less aggressive on the skin's surface. Coarse scrubs create micro-lesions; if you are attached to a scrub, keep it for the body.