Ingredient Comparison
AHA vs BHA
AHAs and BHAs are the two main families of exfoliating acids. AHAs, such as glycolic, lactic and mandelic acid, dissolve in water and work on the skin’s surface. BHA, which in skincare almost always means salicylic acid, dissolves in oil and works inside pores.
Choose an AHA if your skin is dry, rough, dull or showing sun damage; lactic or mandelic acid are gentler starting points than glycolic acid. Choose a BHA if your skin is oily, congested or prone to blackheads. If you have combination skin, start with whichever matches your biggest concern, and add the other on separate days only if you need it.
- AHAs work on the surface and suit dry, dull or rough skin; BHA works inside pores and suits oily, congested skin.
- Not all AHAs feel the same: lactic acid is reported to be less irritating than glycolic acid.
- AHAs increase sun sensitivity, so daily sunscreen is essential while using them and for a week after stopping.
At a glance
How AHAs and BHAs differ
Both families exfoliate. The practical differences are where they work, which skin types they suit and how they affect sun sensitivity.
| Factor | AHA (alpha hydroxy acids) | BHA (beta hydroxy acid) |
|---|---|---|
| Common examples | Glycolic, lactic and mandelic acid. | Salicylic acid. |
| How it dissolves | Water-soluble; works mainly on the outer surface layer. | Oil-soluble; mixes with sebum (skin oil) and works inside pores. |
| Best-matched skin | Dry, normal, rough or sun-damaged skin. | Oily, combination or acne-prone skin. |
| Best-matched concerns | Dullness, rough texture, uneven tone and dryness. | Blackheads, whiteheads and clogged pores. |
| Extra effects | Lactic acid also helps hydrate dry skin. | Mild anti-inflammatory action, because it is related to aspirin. |
| Typical leave-on strengths | Cosmetic products considered safe at 10% or less, with a pH of 3.5 or higher. | 0.5% to 2% in over-the-counter acne products. |
| Sun sensitivity | Increases UV sensitivity; fades about a week after stopping. | A controlled study found no significant increase; FDA still advises sun protection. |
| Pregnancy | Glycolic acid has no published reports of harm. | Low risk on small areas; AAD suggests limiting strengths above 2%. |
Evidence profile
How confident is this comparison?
Confidence is shown in plain categories, not a numerical score.
Both families are widely studied, but much of the comparative evidence uses in-clinic peels or glycolic and salicylic acid specifically, not every acid in each family.
AHAs loosen surface cell bonds, and small studies support improvement in sun-damaged texture and dry skin.
Salicylic acid is lipid-soluble and concentrates in the pore lining, and it is conditionally recommended for acne in the 2024 US guideline.
In a controlled study, 10% glycolic acid increased UV-induced redness and DNA damage, while 2% salicylic acid caused no significant change.
Glycolic acid is the best studied. Lactic and mandelic acid are often called gentler, but fewer trials compare them directly in everyday products.
Choose by goal
Which one fits your skin?
Your skin type and main concern usually point clearly to one family. You rarely need both from the start.
Dry, flaky or tight skin
An AHA such as lactic acid exfoliates while helping hold water in the skin, which suits dry skin.
Lean toward: AHA, ideally lactic acid
Shiny skin with clogged pores
BHA dissolves in oil and reaches into pores, which suits oily skin and congestion.
Lean toward: BHA
Blackheads and whiteheads
Salicylic acid works where blackheads form, inside the pore lining.
Lean toward: BHA
Dullness, rough texture or sun damage
AHAs are the better-studied family for surface renewal and sun damage. Daily sunscreen is part of the deal.
Lean toward: AHA
Oily T-zone, drier cheeks
Start with the acid for your biggest concern. Some people use BHA on the T-zone and an AHA elsewhere, on different nights.
Lean toward: Start with one
Your skin reacts easily
Try a gentle option such as mandelic acid or a PHA, once or twice a week, or wait until irritation settles.
Lean toward: A gentle AHA or PHA
Strengths and limits
What each acid family does well, and where it falls short
AHA
Where it does well
- Smooths rough texture and dullness
- Lactic acid also helps hydrate dry skin
- Options range from gentle to strong
- Supported for sun-damaged skin in small studies
Where it falls short
- Increases sun sensitivity while in use
- Glycolic acid can sting and peel
- Works on the surface, not deep in pores
BHA
Where it does well
- Works inside oily pores
- Targets blackheads and whiteheads
- Mild anti-inflammatory action
- Did not raise sun sensitivity in a controlled study
Where it falls short
- Less suited to dry or flaky skin
- Limited effect on surface dullness
- Only one common ingredient to choose from
- Not for large areas over long periods
Starting an exfoliating acid
How to start without over-exfoliating
Match the acid to your skin
Dry or dull skin points to an AHA; oily or congested skin points to a BHA.
Start two or three times a week
Apply in the evening on clean, dry skin, then follow with a plain moisturizer.
Watch for over-exfoliation
Stinging with every product, tightness, shine or flaking means you should cut back or pause.
Judge results at 6 to 8 weeks
Give one acid a fair trial before switching or adding another.
Using both and routine fit
Can you use AHA and BHA together?
Using both
You can, but there is little reason to start that way. Alternate nights work better than layering, and combination products are best saved for skin that already tolerates one acid.
What pairs well
Niacinamide, ceramides and a simple moisturizer pair well with either. Keep retinoids and benzoyl peroxide on separate nights unless a clinician advises otherwise.
Why AHA products carry a sunburn warning: FDA recommends a sunburn alert on AHA products. They can make skin more prone to sun damage while in use and for about a week afterward. FDA also advises sun protection with BHA products, so daily sunscreen is wise with either.
Safety and professional-help boundaries
When this choice needs more than a product switch.
- Do not apply exfoliating acids to sunburned, broken or actively irritated skin.
- If your skin stings with every product, looks shiny and tight or flakes, you may have over-exfoliated skin; pause all acids until it settles.
- Avoid using salicylic acid over large areas for long periods, especially in children, because of the rare risk of salicylate poisoning.
- Persistent burning, swelling or a rash is not normal; stop and seek medical advice.
- Use a broad-spectrum SPF 30 or higher every morning, especially while using an AHA.
Frequently asked questions
Short answers to common questions
What is the difference between AHA and BHA?
AHAs, such as glycolic and lactic acid, are water-soluble and exfoliate the skin’s surface. BHA, which in skincare means salicylic acid, is oil-soluble and works inside pores, so it suits oily and congested skin.
Is AHA or BHA better for acne?
BHA is usually the better fit for blackheads and clogged pores because it works inside the pore. For inflamed or persistent acne, treatments such as benzoyl peroxide or adapalene have stronger evidence than either acid family.
Is AHA or BHA better for dry skin?
AHAs, especially lactic acid, are generally the better choice for dry skin. They exfoliate the surface and lactic acid also helps hydrate, while BHA can feel drying.
Can I use AHA and BHA together?
Yes, but most people do better starting with one. If you add the other, use them on alternate nights rather than layering them, and stop if your skin becomes tight, red or flaky.
Does BHA make you sensitive to the sun?
A controlled study found that 2% salicylic acid did not significantly increase UV sensitivity, unlike 10% glycolic acid. FDA still advises sun protection with BHA products, so daily sunscreen remains sensible.
Which AHA is the gentlest?
Lactic acid is reported to be less irritating than glycolic acid, and mandelic acid is often used for sensitive skin. PHAs are a related, gentler group to consider if AHAs sting.
How often should I use AHA or BHA?
Start two or three evenings a week and increase slowly only if your skin stays comfortable. More often is not always better, and over-exfoliation can damage the skin barrier.
Editorial Record
- Editorial status
- reviewed
- Medical reviewer
- Dr. Abdurrahman Efem
- Practical reviewer
- Merve Akkaya
- Last reviewed
- November 13, 2026
Related pages
Continue from here
Compare and go deeper
Side-by-side comparisons and practical guides
Sources reviewed
Evidence behind this comparison
- Kornhauser A, Coelho SG, Hearing VJ. Applications of hydroxy acids: classification, mechanisms, and photoactivity. Clinical, Cosmetic and Investigational Dermatology, 2010.
- Kornhauser A, et al. The effects of topically applied glycolic acid and salicylic acid on ultraviolet radiation-induced erythema, DNA damage and sunburn cell formation in human skin. Journal of Dermatological Science, 2009.
- Arif T. Salicylic acid as a peeling agent: a comprehensive review. Clinical, Cosmetic and Investigational Dermatology, 2015.
- Tang SC, Yang JH. Dual effects of alpha-hydroxy acids on the skin. Molecules, 2018.
- US Food and Drug Administration: Alpha hydroxy acids.
- US Food and Drug Administration: Beta hydroxy acids.
- Bergfeld WF. Cosmetic use of alpha-hydroxy acids. Cleveland Clinic Journal of Medicine, 1997.
Sources support the general editorial conclusions shown here. They do not replace personal medical advice from a qualified clinician, and they do not prove that every product containing these ingredients will perform the same way.