AHAs and BHAs are chemical exfoliants that loosen the bonds between dead skin cells so they shed evenly, without the scratching of a physical scrub. Alpha hydroxy acids (AHAs) are water-soluble and work on the skin's surface, so they suit dull, dry or sun-damaged skin. Beta hydroxy acid (BHA, salicylic acid) is oil-soluble, so it works inside the pore and suits oily, congested or acne-prone skin. Used gradually and with daily SPF, both are among the most reliable everyday tools for smoother, brighter skin.
This guide is written by Dr Vishal Patel at Dental & Wellness London in Islington. It explains how each acid works, how to choose one for your skin type, and how to introduce it without irritation. If you would rather have a clinician choose for you, our professional chemical peels use the same acids at controlled, in-clinic strengths.
AHA vs BHA: the core difference
The difference comes down to solubility. AHAs dissolve in water, so they act on the outermost layer of skin, evening tone and texture and improving how light reflects from the surface. BHAs dissolve in oil, so they travel into the follicle and clear the mix of sebum and dead cells that forms blackheads and whiteheads. Many people with combination skin use both: a BHA on the T-zone and an AHA elsewhere, on different evenings.
The AHA family
- Glycolic acid has the smallest molecule and penetrates furthest, so it gives the most visible resurfacing but is also the most likely to sting. Best for normal, resilient skin with dullness or early sun damage.
- Lactic acid is a larger molecule and also helps the skin hold water, so it suits drier and more sensitive skin.
- Mandelic acid is larger again and penetrates slowly, which makes it a gentle choice for sensitive skin and for darker skin tones that are prone to pigmentation after irritation.
- Tartaric and citric acids usually appear in blends to support the main acid rather than on their own.
The BHA family
Salicylic acid is the main BHA in skincare, usually at 0.5–2% in leave-on products. As well as clearing pores, it has a mild anti-inflammatory effect, which is why it is a mainstay of an evidence-based acne routine. People with an aspirin allergy should avoid it.
Choosing by skin type
- Oily or congested skin: salicylic acid two to three times a week, building up as tolerated.
- Dull or uneven skin: glycolic or lactic acid once or twice a week. See our page on dull skin for in-clinic options.
- Dry or sensitive skin: lactic or mandelic acid once a week, with a simple moisturiser afterwards.
- Pigmentation-prone skin: mandelic or low-strength lactic acid, with strict daily SPF; our pigmentation page explains clinical treatment.
How to use chemical exfoliants
Start with one evening a week on clean, dry skin and increase slowly over four to six weeks. Expect mild tingling; stop if you see persistent redness, burning or flaking. Avoid using an acid on the same evening as a retinoid until your skin is used to both, and do not exfoliate broken, sunburnt or freshly waxed skin. Acids make skin more sensitive to the sun, so a broad-spectrum SPF 30 or higher every morning is essential.
Why chemical exfoliation beats physical scrubs
Scrubs remove dead cells by friction, which tends to be uneven and can leave micro-tears, particularly on acne-prone or sensitive skin. Chemical exfoliants work evenly across the surface at a controlled strength, so the result is more predictable and kinder to the skin barrier.
Common mistakes
- Using several acid products at once, or daily from the start.
- Skipping sunscreen.
- Expecting overnight change: visible improvement usually takes four to eight weeks of regular use.
- Continuing through irritation rather than pausing to let the barrier recover.
Exfoliating in pregnancy
Low-strength lactic and mandelic acids are generally considered acceptable during pregnancy, and leave-on salicylic acid is best discussed with your midwife or GP, though some practitioners advise caution. High-strength chemical peels are deferred until after pregnancy.
Cost
- Drugstore chemical exfoliants: £8-£25
- Mid-range: £20-£60
- Professional-formulary: £60-£150+ (compare in-clinic options in our guide to HydraFacial, microdermabrasion and chemical peels)
- Skin consultation at DWL: £65, redeemable in full against treatment
Book a consultation
Free 20-minute discovery call. Skin consultation £65, redeemable in full against treatment, includes a chemical exfoliation recommendation. Clinic options include medical-grade facials.
