What is the difference between AHA and BHA?

AHAs (alpha hydroxy acids) are water-soluble and work on the surface of the skin to loosen dead skin cells. Common AHAs include glycolic acid and lactic acid. BHAs (beta hydroxy acids) are oil-soluble and can penetrate inside the pore lining — the most common BHA is salicylic acid. This difference makes BHAs particularly effective for oily and acne-prone skin.

Can you use AHA and BHA together?

Yes, but with care. Some products combine low concentrations of both. If using separate products, apply on alternating evenings rather than layering them in the same routine — using both simultaneously increases the risk of over-exfoliation. Always follow with a moisturiser and use SPF the following morning.

Which is better for acne?

BHA (salicylic acid) is generally better for active acne. Because it is oil-soluble, it can penetrate inside the pore to break down the sebum and dead skin cells that cause congestion. AHAs are more useful for post-acne marks (PIH) and surface texture, but are less effective inside the pore.

Which is better for anti-ageing?

AHAs, particularly glycolic acid at higher concentrations (8–10%+), have stronger evidence for improving fine lines, skin texture, and collagen stimulation. Lactic acid is a gentler AHA option with humectant properties. BHA has some anti-ageing benefits but is primarily used for oil control and pore clearing.

How often should I use chemical exfoliants?

Most people do well with 2–3 times per week for either AHA or BHA. Daily use is possible with very low concentrations (some toners contain 1–2% AHA for gentle daily use) but higher concentrations need more recovery time. If your skin becomes red, tight, or sensitive, reduce frequency. Over-exfoliation is one of the most common causes of damaged skin barrier in skincare enthusiasts.

Ingredient Comparison

AHA vs BHA

AHAs (like glycolic acid and lactic acid) are water-soluble exfoliants that work on the skin surface — best for dryness, dullness, and anti-ageing. BHAs (like salicylic acid) are oil-soluble and penetrate inside the pore — best for oily, acne-prone, and congested skin. Both increase photosensitivity, so SPF is essential when using either.

Sarah TaylorK-Beauty Specialist

BSc Cosmetic Science · 12 years in Korean skincare · Former K-beauty product consultant

Published June 2025 · Last reviewed June 2025

TL;DR — Quick Summary

✦AHAs are water-soluble — they exfoliate the skin surface. Best for dry, dull, and ageing skin.
✦BHAs are oil-soluble — they exfoliate inside the pore. Best for oily, acne-prone, and congested skin.
✦Salicylic acid is the most common BHA; glycolic and lactic acid are the most common AHAs.
✦Both increase sun sensitivity — always use SPF the morning after.
✦Use 2–3 times per week maximum; over-exfoliation damages the skin barrier.

Factor	AHA	BHA
Solubility	Water-soluble	Oil-soluble
Where it works	Skin surface	Inside the pore
Common types	Glycolic acid, lactic acid, mandelic acid	Salicylic acid (most common)
Best for	Dryness, dullness, fine lines, hyperpigmentation	Oily skin, acne, blackheads, congestion
Anti-ageing evidence	Strong (especially glycolic at 8%+)	Moderate
Increases photosensitivity?	✓ Yes	✓ Yes
Safe for sensitive skin?	Lactic & mandelic acid — yes. Glycolic — use caution	Often yes, at low % (0.5–1%)
Typical concentration	5–10% (treatment); 1–2% (daily toner)	0.5–2% (daily); 2–4% (treatment)

Frequently Asked Questions

Ingredient guide

Salicylic Acid (BHA) →

Ingredient guide

Azelaic Acid →