Is AHA or BHA better for acne?

BHA is usually the better choice for acne. Salicylic acid is oil-soluble, so it can get inside pores and loosen the oil and dead cells that form blackheads and whiteheads, and it has mild anti-inflammatory effects. AHAs can help fade post-acne marks, but they don't reach into pores the same way. For red, inflamed pimples, benzoyl peroxide may be needed alongside BHA.

Can I use AHA and BHA on the same day?

You can, but most people do better alternating them on different nights, especially at first. Using both at once increases the chance of redness, stinging and barrier damage. If your skin is oily and resilient, a product formulated with both acids, or applying BHA to your T-zone and AHA to your cheeks, can work. Avoid adding a retinoid on the same night.

Which is gentler, AHA or BHA?

It depends on the specific acid. Among AHAs, mandelic and lactic acid are gentler than glycolic acid because their larger molecules penetrate more slowly. Salicylic acid at 0.5–2% is generally well tolerated but can feel drying. PHAs such as gluconolactone are usually the gentlest option for sensitive skin. Whatever you choose, start two to three nights a week.

Do I need sunscreen when using AHA or BHA?

Yes. AHAs in particular make skin more sensitive to UV, and the FDA requires AHA products sold in the US to carry a sunburn alert because that sensitivity can last up to a week after use. Use a broad-spectrum SPF 30 or higher every morning while using any exfoliating acid, and reapply when you're outdoors for long periods.

How long does it take for AHA or BHA to work?

Skin often feels smoother within a week or two, but visible changes in clogged pores, dullness or dark spots usually take four to six weeks of consistent use. Improvements in fine lines and sun-damaged texture can take eight to twelve weeks. If you see no change after about three months, or you're getting irritation, consider adjusting the product or asking a dermatologist.

AHA vs BHA: Which Exfoliant Should You Use?

Choose a BHA (salicylic acid) if your main concerns are oily skin, blackheads, clogged pores or breakouts. Choose an AHA (glycolic, lactic or mandelic acid) if you want to smooth dry or rough texture, fade dullness and dark spots, or soften the look of fine lines. If you have combination skin with a bit of both, you can use both — just not in a way that over-exfoliates your skin.

The difference comes down to solubility. AHAs are water-soluble, so they work mainly on the surface, loosening the "glue" between dead skin cells. BHAs are oil-soluble, so they can move into oily pores and clear out the debris that turns into blackheads and pimples. Neither is "stronger" or "better" overall; they solve different problems.

Below, we break down how each acid works, which concentrations make sense for at-home use, how to combine them safely, and the mistakes that most often lead to irritation.

What AHAs and BHAs actually do

Both are chemical exfoliants. Instead of scrubbing dead cells off with grains or brushes, they loosen the bonds that hold dead cells to the skin's surface so those cells shed more evenly. The result, with consistent use over a few weeks, is skin that feels smoother, looks brighter and absorbs moisturizer more evenly.

Where they differ is where they work:

AHAs (alpha hydroxy acids) dissolve in water. They act on the outermost layer of skin, which is why they are good at improving rough texture, flakiness and uneven tone. Some AHAs, especially lactic acid, also act as humectants, helping the skin hold on to water.
BHAs (beta hydroxy acids) dissolve in oil. Salicylic acid — the only BHA you'll find in most skincare — can penetrate the oil inside pores and exfoliate the lining of the pore itself. It also has mild anti-inflammatory properties, which is part of why it is a staple in over-the-counter acne products.

The main types of AHAs

Not all AHAs behave the same. Molecule size affects how deeply and quickly an acid penetrates, which affects both results and irritation.

Glycolic acid has the smallest molecule, so it penetrates most readily. It is the most studied AHA for texture, dullness and photoaging, but it is also the most likely to sting.
Lactic acid is a larger molecule and is generally gentler. Its hydrating effect makes it a common pick for dry skin and first-time acid users.
Mandelic acid is larger still and penetrates slowly, which makes it one of the gentler options. It is often suggested for sensitive skin and for people with deeper skin tones who want to lower the risk of post-inflammatory hyperpigmentation from irritation.
Citric, malic and tartaric acids usually appear in lower amounts as supporting ingredients rather than the main exfoliant.

You may also see PHAs (polyhydroxy acids) like gluconolactone. These are close cousins of AHAs with an even larger molecule, and they're usually the gentlest option of all — worth considering if regular AHAs leave your skin red.

AHA vs BHA at a glance

	AHA (glycolic, lactic, mandelic)	BHA (salicylic acid)
Dissolves in	Water	Oil
Works mainly on	Skin surface	Surface and inside pores
Best for	Dryness, rough texture, dullness, dark spots, fine lines	Blackheads, whiteheads, oily skin, breakouts, visible pores
Typical OTC strength	Up to about 10% in leave-on products	0.5–2%
Hydrating effect	Lactic acid especially	No — can feel drying
Calming effect	No	Mildly anti-inflammatory
Watch out for	Stinging, sun sensitivity	Dryness; avoid if allergic to aspirin

Which one should you choose? (By skin type and concern)

Oily or acne-prone skin: start with BHA

If your T-zone gets shiny by midday, or you deal with blackheads, whiteheads and small breakouts, salicylic acid is the logical first choice. Because it reaches into the pore, it targets the clog that starts most acne lesions. A 2% leave-on toner or serum a few nights a week is a common starting point. For a deeper look at blackheads specifically, see our guide on how to get rid of blackheads.

If you have inflamed red pimples, salicylic acid alone may not be enough; benzoyl peroxide targets acne-causing bacteria in a way BHA doesn't. Our comparison of salicylic acid vs benzoyl peroxide explains how they differ.

Dry, dull or rough skin: start with AHA

If your skin feels tight, looks flat, or has a sandpaper-like texture, an AHA is usually the better fit. Lactic acid at 5–10% is a good beginner option because it exfoliates while helping hold in moisture. Always follow with a moisturizer.

Dark spots and uneven tone: usually AHA

AHAs help shed pigmented surface cells faster, which can make sun spots and post-acne marks fade more evenly over time when paired with daily sunscreen. If those marks come with ongoing breakouts, a BHA can help prevent new ones — so this is a case where using both (on different days) often makes sense.

Fine lines and sun-damaged texture: AHA

Glycolic acid has the most research behind it for smoothing the look of photoaged skin. Expect subtle changes over 8–12 weeks, not overnight transformations. For deeper wrinkles, a retinoid usually has more impact; see how to use retinol if you want to add one later.

Sensitive skin or rosacea: go slow, or skip

Sensitive skin can still benefit from exfoliation, but gentler options — mandelic acid, PHAs or a low-strength salicylic acid — used once or twice a week are a safer start. If you have rosacea or eczema, check with a dermatologist before adding any acid, since flare-ups are common.

Combination skin: both, used strategically

Many people have an oily T-zone and drier cheeks. You can apply BHA only where you get congested and AHA (or nothing) elsewhere, or alternate them on different nights. The right mix depends on your skin type, concerns and what else is in your routine — if you're unsure where to start, our free 3-minute skin assessment builds a routine around your answers.

Can you use AHA and BHA together?

Yes, but "together" doesn't have to mean "at the same time." Three common approaches, from gentlest to most intensive:

Alternate nights. Use BHA one night and AHA another, with plain moisturizer-only nights in between. This is the easiest way to get the benefits of both while limiting irritation.
Zone them. BHA on your nose, chin and forehead; AHA on your cheeks.
Use a combined product. Some formulas contain both, at strengths designed to be used together. This can work well for resilient, oily skin, but it's not the best starting point if you're new to acids.

What you generally shouldn't do is layer a strong AHA serum, a BHA toner and a retinoid in the same routine. Stacking multiple exfoliating actives is one of the fastest ways to damage your skin barrier.

How to start using an AHA or BHA

A simple, low-risk way to introduce either acid:

Pick one acid first. Don't start AHA and BHA in the same week. If you react, you won't know which caused it.
Patch test. Apply a small amount along your jawline for a few days before using it on your whole face.
Start 2–3 nights a week. Apply to clean, dry skin in the evening. Leave-on products (toners, serums) are more effective than cleansers, which rinse off quickly — but cleansers are a gentle way to start.
Follow with moisturizer. Look for one with ceramides, glycerin or panthenol to support the barrier.
Wear sunscreen every morning. This step is non-negotiable (more on why below).
Increase slowly. If your skin is comfortable after two to three weeks, you can add a night. Many people never need more than 3–4 nights a week. Our guide on how often to exfoliate covers frequency by skin type in more detail.

Mild tingling for a minute or two is common at first. Burning, lasting redness, peeling or a tight, shiny look means you're overdoing it — stop until your skin calms down, then restart less often.

Sunscreen, safety and common mistakes

AHAs increase sun sensitivity. The FDA requires AHA products sold in the US to carry a "sunburn alert" because AHAs can make skin more sensitive to UV for up to a week after use. Use a broad-spectrum SPF 30 or higher every day while using acids — not only on days you apply them. The American Academy of Dermatology's tips on how to safely exfoliate at home make the same point.

Watch the concentration. For leave-on, at-home products, AHAs at about 10% or below and salicylic acid at 0.5–2% are the standard OTC range. Higher-strength "peels" are best done by, or with guidance from, a dermatologist.

Other mistakes we see often:

Using a physical scrub on the same day as an acid
Applying acids on broken, sunburned or freshly waxed skin
Combining acids with a retinoid on the same night when you're just starting out
Expecting results in days — most people see a difference in 4–6 weeks
Continuing through irritation instead of pausing

Special situations. Salicylic acid is chemically related to aspirin, so skip it if you have an aspirin allergy. If you're pregnant or breastfeeding, ask your doctor before using salicylic acid, especially high-strength or full-body products; low-strength AHAs such as lactic or glycolic acid are often considered a lower-risk option, but it's still worth confirming.

When to see a dermatologist

Consider booking an appointment if:

Your acne is painful, cystic or leaving scars despite a few months of OTC treatment
You develop persistent redness, burning or rash after using an acid, even after stopping
You have rosacea, eczema or psoriasis and want to exfoliate safely
Dark spots aren't fading after three months of consistent use and daily sunscreen, or a spot changes in size, shape or color
You're interested in professional chemical peels

A dermatologist can recommend in-office peels or prescribe stronger topical treatments, such as prescription retinoids, when OTC acids aren't enough.

The bottom line

AHAs and BHAs are both effective chemical exfoliants, but they're built for different jobs. BHA (salicylic acid) works inside oily pores, making it the go-to for blackheads, breakouts and oily skin. AHAs (glycolic, lactic, mandelic) work on the surface, making them better for dryness, dullness, uneven tone and texture. Start with one, use it two to three nights a week, moisturize, and wear sunscreen daily. If your skin tolerates it well, you can add the other on alternate nights — and if it doesn't, less is almost always more.

This article is for general informational purposes and does not constitute medical advice. If you have a persistent or severe skin concern, consult a board-certified dermatologist.