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AHAs, BHAs, and how to choose between them. The category where more is not more — twice a week is the ceiling.
151 how-to's · Updated 27 April 2026 · Avg. 4 min per piece · Edited by Nelly · Beauty & Style Director
Editor's note
Chemical exfoliants are not the more-is-more category. Twice a week is the ceiling for most faces. The AHA group works on the surface. The BHA, salicylic acid, goes into the pore. Different mechanisms for different problems.
Other ingredients
What chemical exfoliation actually is
Chemical exfoliation uses acids to loosen and dissolve the bonds between dead skin cells, rather than scrubbing them off. Done correctly, it produces smoother texture and more even tone. Done too often, it is barrier damage that takes weeks to repair.
Myth, meet fact
- Myth: More exfoliation gives faster results. Fact: It accelerates barrier breakdown. Two nights a week is a ceiling, not a starting point.
- Myth: AHAs and BHAs do the same thing. Fact: AHAs exfoliate the surface. BHAs go into the pore.
- Myth: Chemical exfoliants make your skin thinner. Fact: Controlled exfoliation over time can thicken the epidermis. Over-exfoliation thins it.
Sub-topics on this page
AHAs — glycolic, lactic, mandelic
Alpha hydroxy acids work on the surface of the skin. Glycolic has the smallest molecule and deepest penetration. Lactic is gentler and also a humectant. Mandelic is the most tolerated on reactive or darker skin. Twice a week is the standard ceiling.
BHA — salicylic acid
Salicylic acid is oil-soluble, which allows it to penetrate the pore lining. The right choice for congestion, blackheads, and oily skin. 0.5–2% is the functional range.
Choosing between AHAs and BHA
Surface texture, tone, and fine lines respond to AHAs. Congestion and blackheads respond to BHA. Most people find they need one, not both.
The beginner's path
- AHAs: glycolic, lactic, mandelic — what makes each different (5 min)
- BHA: salicylic acid — the pore-focused one (4 min)
- How often to exfoliate — the honest answer (3 min)
- Choosing between AHA and BHA (4 min)
- Chemical exfoliants with retinoids — the alternating schedule (4 min)
Format and cadence
Glycolic acid toner for surface texture. Lactic acid for gentler AHA use. Mandelic acid for sensitive skin. Salicylic acid 0.5–2% for congestion and pores. AHA + BHA combination once a week maximum.
Everything we've published on chemical exfoliants
- Glycolic vs lactic acid — which to start with
- Salicylic acid for blackheads — the correct approach
- AHAs and BHAs in the same routine
- Mandelic acid — the exfoliant for sensitive skin
- How often to exfoliate — the plain-English answer