Scrubs with grains have lost the argument: modern exfoliation is done with acids. But “exfoliating acid” covers two families that do quite different jobs, and choosing the wrong one means, at best, seeing no change and, at worst, irritating your skin for nothing.
In short
AHAs (glycolic and lactic acid) are water-soluble chemical exfoliants that work on the surface of the skin; BHA (salicylic acid) is oil-soluble and goes down into the pores. Choose an AHA for radiance and skin texture, and a BHA for blackheads and the T-zone. Either way: two to three evenings a week, never the same evening as retinol, and an SPF every morning.
The difference in one sentence
AHAs work on the surface of the skin; BHA goes down into the pores. Everything else — which product, for which goal, how often — follows from that sentence.
The comparison
| AHA (glycolic, lactic…) | BHA (salicylic acid) | |
|---|---|---|
| Soluble in | Water, so it works on the surface | Oil, so it goes into the pores |
| What it improves | Radiance, and the appearance of skin texture and marks | The appearance of blackheads and congested pores |
| Typical profile | Normal to dry skin, dull complexion | Oily T-zone, combination skin, blemishes |
| Relative gentleness | Lactic is the gentlest of the AHAs | Generally well tolerated at a low concentration |
| Key precaution | Sun sensitivity: SPF is a must | Take care with high strengths during pregnancy |
If your main concern is blackheads, the answer is BHA: it is the only one of the two that goes after them where they form. If your concern is a complexion that lacks radiance, it is AHA.
The rules that apply whichever you choose
- Two to three times a week is enough. Daily exfoliation is rarely useful and often counterproductive: over-exfoliated skin feels tight, turns red and gets shinier.
- In the evening, and never the same evening as retinol. You alternate active evenings rather than stacking them. That is the whole principle of skin cycling, in its sensible version.
- SPF in the morning, without exception. AHAs in particular increase the skin’s sensitivity to the sun. That is documented by the FDA and is not excess caution. An exfoliant without sun protection the next day is one step forward and two steps back.
- One exfoliant at a time. AHA and BHA in the same routine is only for skin that already tolerates everything, and even then the benefit is debatable.
How to tell whether it is working
Give it six weeks, at two or three applications a week. Encouraging signs: skin that feels smoother to the touch, a more even complexion, pores that look less congested. Warning signs: persistent tightness, redness, a raw feeling. That means over-exfoliation, so space it out or stop while your skin rebalances.
And if you are still undecided between the two families after all this, perhaps exfoliating is not your priority. A solid basic routine of cleanse, moisturise and protect changes the appearance of skin more than any acid applied on top of shaky foundations.
The last word
AHA for the surface, BHA for the pores, never every day, always SPF. Follow those four rules and exfoliation goes from irritating gimmick to a quiet lever that makes a difference over time.
Frequently asked questions
Can you use an AHA and a BHA at the same time?
It is rarely useful. One exfoliant at a time is enough for most skin, and combining them mainly raises the risk of irritation. If you want both, alternate them on different evenings.
Can you exfoliate on the same evening as retinol?
No. The American Academy of Dermatology points out that retinol already makes skin more sensitive, and that exfoliating on top can dry it out further. Alternate instead: exfoliant one evening, retinol another.
Should you moisturise after an exfoliant?
Yes. Exfoliation can dry the skin out, so a moisturiser straight afterwards helps keep it comfortable.
Why is SPF essential with an AHA?
Because AHAs increase the skin’s sensitivity to the sun, as the FDA documents. Sun protection every morning stops the evening’s exfoliation from working against you.