AHA vs BHA vs PHA: Which Exfoliant Suits Your Skin Type?

I'm Dr. Hongseok Kim, a board-certified Korean dermatologist with 21 years of practice and the medical director of VOS Dermatology Clinic in Gangnam, Seoul, in front of Dosan Park. At VOS I see every patient myself, from the consultation to the treatment.

"AHA vs BHA, which one do I need?" is a question I hear every time the seasons change and skin starts to flake. Some people say never exfoliate, others say always exfoliate; neither is right, because it depends on your skin. This page is based on my YouTube video from October 2024, where I explain the three exfoliating acids, how often to use them and who should hold back; I rewrote it for readers abroad. The video above can be watched with translated captions.

Physical scrubs or chemical exfoliants?

Short answer: I don't prefer scrubs and grainy products; if you exfoliate, use the acids in your skin care instead (in the video at 00:52).

When day and night temperatures swing in autumn, many people find their skin rough and flaky (in the video at 00:28). There are two ways to deal with it: remove dead skin physically, with grains or gommage-type products, or let ingredients in a product loosen it. Physical exfoliation can leave skin sensitive and cause more problems later, so I'm not a fan (in the video at 01:06). If you are going to exfoliate, the ingredients approach is the one I recommend. There are only three to remember: alpha hydroxy acids (AHA), beta hydroxy acid (BHA) and polyhydroxy acids (PHA) (in the video at 01:29).

AHA: for most skin, at low strength

Short answer: AHAs such as glycolic and lactic acid can be used on any skin type at the small amounts found in cosmetics, but I don't recommend chasing high strengths (in the video at 01:42).

People who want faster results look for 5% or 10% glycolic acid. I don't recommend that (in the video at 02:05). If your skin is completely healthy, it may be fine; if not, the chance of sensitivity, irritation and redness is high. Choosing a lower-strength product helps more.

Here is how these acids work. Skin renews itself: cells from the bottom layer of the epidermis move up and are finally shed, a cycle of about a month (in the video at 02:34). That last shedding step depends on pH. Skin sits at about pH 4.5 to 5.5, lower than the rest of the body, and when pH drops, enzymes that let surface cells separate become more active (in the video at 03:01). Tightly packed dead cells loosen, moisturizing ingredients slip into the gaps, and skin looks smoother and more hydrated. Exfoliating acids use this principle.

BHA: for oily and acne-prone skin

Short answer: BHA, mainly salicylic acid, dissolves sebum, so it is the usual choice for oily or acne-prone skin (in the video at 03:41).

If your face produces a lot of oil or breaks out easily, salicylic acid is the typical exfoliant. If breakouts are frequent or deep, though, an acid alone won't be enough, which I explain in my page on Korean face care for acne and its limits.

PHA: for sensitive skin

Short answer: PHAs such as gluconolactone have larger molecules that penetrate less, so they are gentle enough for sensitive skin (in the video at 03:58).

A polyhydroxy acid is, as the name says, a molecule with many hydroxy groups. Because each molecule is larger, it doesn't penetrate deeply, so it is less likely to irritate. That is why PHA is used as the exfoliant for sensitive skin.

How often, and which acid for which skin type

Short answer: two to three times a week, about twice for sensitive skin and three times, alternating, for sturdy skin (in the video at 04:53).

Using an exfoliant every day lets your skin get used to the faster turnover, so you stop feeling the effect, and if that continues, skin becomes sensitive (in the video at 04:36). By skin type (in the video at 05:09):

• Dry skin: PHA or AHA.
• Oily skin: AHA, BHA and PHA are all fine.
• Sensitive skin: PHA such as gluconolactone; if sensitivity is mild, AHA can also be enough.

When you read an ingredient list, remember that ingredients near the front are present in larger amounts and those near the end in smaller amounts. An acid listed toward the back is a gentler place to start (in the video at 05:35).

Exfoliating toner pads help too, since most contain AHA, BHA or PHA. Soak the pad generously instead of dabbing a little on it, and wipe gently; that cuts friction. Very sensitive skin should skip them, and for everyone else, a leave-on product alone can be enough (in the video at 06:01). If you would rather have dead skin cleared in the clinic, HydraFacial at VOS combines gentle exfoliation, deep cleansing and serum infusion in about 30 minutes, and my guide to Korean HydraFacial explains when it fits.

Who should hold back from exfoliating

Short answer: dry, sensitive skin such as atopic dermatitis and oily, sensitive skin such as rosacea need caution; if treatment is needed, choose with your doctor (in the video at 07:18).

Oily, acne-prone skin with large pores can run into trouble with a cleanser that is too mild, because sebum is not cleared; these people benefit from a deeper cleanser combined with exfoliation (in the video at 06:56). At the other end, the typical problem for dry, sensitive skin is atopic dermatitis, and for oily, sensitive skin it is rosacea. Exfoliating on your own here can make things worse for a long time, so discuss it with a doctor (in the video at 07:34). My guide to Korean rosacea treatment covers that side. Too much is as bad as too little: moderate, regular exfoliation keeps skin healthier (in the video at 07:49). For related habits that make texture worse, see my video note on textured skin, and our creator experiences at VOS show what a visit looks like.

Results vary from person to person, and the right plan for your skin is decided at an in-person consultation.

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Results, swelling and recovery vary from person to person. This page is general information from VOS Dermatology Clinic based on Dr. Kim's video and does not replace an in-person consultation.