Short answer: AHAs and BHA are both exfoliating acids. Alpha hydroxy acids, such as glycolic and lactic acid, are water-soluble exfoliating acids that help loosen dead cells at the skin’s surface. Beta hydroxy acid, which in skincare usually means salicylic acid, is oil-soluble, so it can also work within the opening of a pore. People often reach for an AHA for rough, dull-looking skin and for BHA where oil and congested-looking pores are the concern, but those are tendencies. The complete formulation, and your own skin, decide what suits you.
The two families often sit side by side on ingredient lists, sometimes inside the same product.
What the two have in common
Both are chemical exfoliants. They loosen the bonds that hold dead cells together at the surface, so those cells shed more evenly. Physical vs Chemical Exfoliation explains the two routes.
Both also depend on the product around them. The FDA notes that how much an AHA exfoliates depends on the type and concentration of the acid, its pH and the other ingredients in the product, and salicylic acid products vary with their formulations too. The acid’s name tells you its family, not its strength.
This article covers cosmetic exfoliation. Products sold to address acne are a different category: in the United States they are regulated as over-the-counter drugs, and salicylic acid is one of the ingredients the FDA permits in them.
AHAs: water-soluble acids that work at the surface
The FDA names glycolic acid and lactic acid as the most common AHAs in cosmetics. They are water-soluble exfoliating acids that help loosen dead cells at the surface. Solubility is part of the picture, not a complete explanation of how they work.
Glycolic acid has the smallest molecule of the group. Lactic acid is larger and is often considered gentler. What Is Glycolic Acid, and Who Is It For? goes into the first of these in detail.
BHA: oil-soluble, reaching into the pore opening
In skincare, “BHA” usually means salicylic acid. Chemically, salicylic acid is not a true beta hydroxy acid, as the FDA itself notes, but the label stuck.
You may also see willow bark extract on ingredient lists. It is a botanical extract, not the equivalent of a formulated salicylic acid ingredient.
The useful property of salicylic acid is that it is oil-soluble. It can mix with the oil on your skin and work within the opening of a pore as well as on the surface. Large Pores covers what can and cannot change about how pores look.
Who tends to reach for which
Skin that feels rough or looks dull. AHAs are often chosen here, because the complaint sits on the surface.
Skin that runs oily, with congested-looking pores. BHA is often chosen here, because oil is part of the picture.
Skin that reacts easily. Suitability depends on the whole formulation, not on the acid’s family. Start with informed selection: know what a product is intended to do, whether it suits your skin, how to use it and what it contains. For particularly reactive skin, a small test in an area that makes sense for the product’s intended use can be an additional precaution.
Skin that is cracked, sore, sunburned or currently irritated should not be exfoliated with either acid until it settles. That is different from skin that is generally sensitive, which may still suit a carefully chosen product.
One product with both acids is not stacking
Many products combine AHAs and BHA in one formulation. That is a formulation decision, made with the complete formulation in mind.
Stacking means something else: layering several separate exfoliating products into one routine, such as an acid toner, an acid serum and a scrub. That is where irritation tends to start, and more exfoliation does not bring faster results. Avoid combining multiple exfoliating products unless their directions or your skincare professional specifically recommend doing so, and follow the directions for each.
If you overdo it, the signs are familiar: tightness, stinging from products that never stung, papery flaking and redness that hangs around. Pause, go back to a gentle cleanse and a moisturizer, then resume less often or less intensely. How Often Should You Exfoliate? covers the timing question.
Sun and other products
Research conducted by the FDA found that skin became more sensitive to UV during regular AHA use, and FDA guidance recommends a sunburn alert on AHA cosmetics. The FDA advises sun protection with BHA products too. Daily broad-spectrum sunscreen is recommended as part of the routine either way.
Combining exfoliating acids and retinoids can increase irritation for some people. Retinol is generally used at night, and the directions for each individual product are the ones to follow.
Victoria’s approach
Victoria Nash, founder of Esenté Skincare, has been a licensed aesthetician since 2003. She also owns and operates Younger You Clinique and is an experienced skincare educator. She draws on her professional experience at Younger You Clinique when evaluating skincare products and their performance. Her view of exfoliation applies to both acid families: there is no universal exfoliation schedule. Victoria considers the individual’s age, skin condition, the method of exfoliation and how the skin is responding, and the aim is to exfoliate when needed rather than because a set number of days has passed.
The Esenté range offers different exfoliating approaches rather than a routine to combine. The Liposome Alpha-Beta Serum is an 8% AHA/BHA serum. The Very Berry Exfoliating Cleanser puts exfoliation inside the cleansing step. Oligo-Peel Exfoliation Crème provides physical exfoliation with aluminum oxide, in a formulation that also includes botanical extracts and skin-conditioning ingredients. Each carries its own directions. These are examples, and other Esenté formulations may suit you depending on your individual regimen. If you have known sensitivities, check each complete ingredient list on the Esenté website. Esenté works with boutique manufacturers to develop and select formulations that meet the brand’s ingredient, performance and quality criteria. Weighing one against another? Ask on the Ask Victoria page.
Frequently asked questions
Neither is better as a category. BHA is often chosen for oily skin because it is oil-soluble, but an AHA product can suit oily skin too. The complete formulation and your skin’s response decide it.
Neither family is gentler by definition. Strength depends on the specific acid, its concentration, the pH and the rest of the formulation. Lactic acid is often considered one of the gentler AHAs, but the finished product is what counts.
A single product formulated with both is common and is not the same as stacking. Layering several separate exfoliating products is what tends to cause irritation. Follow the directions for the product you use.
In skincare, yes. Chemically, salicylic acid is not a true beta hydroxy acid, as the FDA notes, but the label is used across the industry.
FDA research found increased UV sensitivity during regular AHA use, and the FDA advises sun protection with BHA products as well. Daily broad-spectrum sunscreen is recommended as part of the routine regardless.
About the author. Victoria Nash, founder of Esenté Skincare, has been a licensed aesthetician since 2003. She also owns and operates Younger You Clinique and is an experienced skincare educator.
Reviewed by Victoria Nash, licensed aesthetician, founder of Esenté Skincare and owner of Younger You Clinique. This article is educational and is not medical advice. Ask your dermatologist or licensed skincare professional about products appropriate for your own skin and medical history.
