Walk down any skincare aisle, and you will meet two sets of initials over and over again. AHA. BHA. They sit on cleansers, serums, toners, and masks, and they are frequently sold as interchangeable. They are not.
Dr. Paul Banwell, founder and clinical director of PANTHEONS Clinic, was recently asked to explain the difference for British Vogue's expert guide to acids. You can read the full feature here: AHA vs BHA: an expert guide, British Vogue.
Below, we have expanded on the topic to help you decide which belongs in your skincare routine.
“A simple way of looking at it is that AHAs tend to be better for concerns on the surface of the skin, while BHAs are particularly good when congestion and oil are involved.” - Dr. Paul Banwell
AHA stands for alpha-hydroxy acid. The family includes glycolic acid, lactic acid, mandelic acid, and citric acid.
AHAs are water-soluble, which means they work across the surface of the skin. They loosen the bonds holding dull, dead cells to the outermost layer, so those cells shed more readily. Skin cell turnover slows with age and with accumulated sun exposure, and that slowdown is a large part of why skin starts to look tired, uneven, or rough to the touch.
AHAs are generally the better choice for:
Glycolic acid has the smallest molecule of the group and penetrates most readily, which makes it effective and also the most likely to sting. Lactic and mandelic acids are larger, slower, and better tolerated by reactive skin.
BHA stands for beta-hydroxy acid, and in skincare that nearly always means salicylic acid.
The important distinction is solubility. BHAs are oil-soluble, so rather than working only across the surface, they travel into the pore lining and break down the mix of sebum and dead cells that sits there. Salicylic acid is also anti-inflammatory, which is why it calms the redness that surrounds a breakout rather than simply drying it out.
BHAs are generally the better choice for:
The honest answer is that it depends less on which acid is stronger and more on what your skin is actually doing.
If your concern is how your skin looks, an AHA is usually the starting point. Dullness, texture, and uneven tone are surface problems, and a surface exfoliant addresses them.
If your concern is what your skin is doing, a BHA is usually the starting point. Congestion, blackheads, and breakouts originate inside the pore, and an oil-soluble acid is the one that can get there.
If your skin is dry, sensitive, or reactive, begin with lactic or mandelic acid two evenings a week and build slowly. If your skin has never met an acid before, begin at the lowest concentration available rather than the highest. Tolerance is built, not assumed.
Yes, though rarely on the same evening when you are starting out.
Many well-formulated products combine both, and for oily skin with visible sun damage that combination can be genuinely useful. The risk is not the pairing itself, but the frequency. Over-exfoliated skin looks tight, feels stripped, stings under moisturiser, and often becomes more reactive and more congested than it was before, which tempts people into exfoliating harder.
A more sustainable approach is to alternate. A BHA on two evenings, an AHA on two others, and simple hydration on the rest of the week will do more for most skin than a daily acid.
Two combinations worth handling with care:
Both acid families increase the skin's sensitivity to ultraviolet light, and AHAs do so substantially. Daily broad-spectrum SPF is not an optional finishing step to an acid routine. It is the part that protects the result.
This matters more at PANTHEONS than a standard skincare disclaimer might suggest. Alongside his aesthetic surgical practice, Dr. Banwell founded MASCU, the Melanoma and Skin Cancer Unit in East Grinstead, and has spent a significant portion of his career in skin cancer surgery and reconstruction. If you are using an acid through the summer and you are not using sun protection, you are removing the layer that absorbs some of that exposure while doing nothing to replace it.
Chemical exfoliants are effective within a defined range. Outside it, they tend to produce disappointment rather than harm.
Acids will not resolve textural change caused by volume loss or laxity. They will not lighten deep dermal pigmentation. They will not flatten a raised or tethered scar. And they will not settle persistent, inflammatory, cystic acne, which is a medical rather than a cosmetic problem and deserves guidance from a dermatologist.
Any new or changing mole, lesion, or patch of skin should be assessed clinically, not treated with an exfoliant.
At PANTHEONS, skin health sits alongside the surgical practice rather than beneath it. A consultation begins with an assessment of what your skin is actually doing, and the recommendation follows from that. Sometimes the recommendation is a better home routine and nothing more.
Is AHA or BHA better for sensitive skin?
Neither category is inherently gentler, but individual acids differ considerably. Mandelic and lactic acids are the most tolerable AHAs because their molecules are larger and penetrate more slowly. Salicylic acid is often well-tolerated by sensitive, breakout-prone skin because of its anti-inflammatory effect. Start at a low concentration, twice weekly, on non-consecutive evenings.
How long before I see a difference?
Texture and brightness usually respond within two to four weeks. Congestion and blackheads often take four to eight weeks. Pigmentation is slower still, and improvement is measured in months rather than weeks.
Should acids go in a morning or evening routine?
Evening, for most people. It reduces the window of ultraviolet exposure on freshly exfoliated skin and avoids layering conflicts with vitamin C.
Can I use acids on my chest and neck?
Yes, and the décolletage is frequently neglected despite showing sun damage early. Use a lower concentration and less frequently than on the face, because the skin there is thinner.
Do I still need in-clinic treatment if I use acids at home?
Not necessarily. Home acids are formulated for maintenance at low concentrations, and for many people that is sufficient. Professional treatment becomes relevant when the concern sits deeper than a home product can reach, which is a judgement best made in person.
Dr. Banwell consults on skin health at the McIndoe Surgical Centre in East Grinstead and at Harley Street in London. Consultations are thorough, and an assessment of your skin is where any recommendation begins.
Book a consultation | Call 01342 330302
This article is general information about skincare ingredients and is not medical advice. Individual assessment is required before beginning any treatment. Dr. Paul Banwell is on the GMC Specialist Register for Plastic Surgery and is a member of BAAPS, BAPRAS, and ISAPS.
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Disclaimer: Please be aware that these notes have been made for purely information purposes and make no recommendations for surgery.
