What is the difference between AHA and BHA?

Solubility, which decides where they work. AHAs are water-soluble and exfoliate the skin surface. BHAs are oil-soluble, so they dissolve into sebum and work inside the pore. That makes BHA the choice for congestion and AHA the choice for surface texture and tone.

It is the maximum for leave-on products under FDA limits, so it is at the ceiling rather than a low dose. The number is not comparable to AHA percentages, which commonly run 10 to 15 percent in consumer products. Different acids, different scales.

Can you use AHA and BHA together?

Most people should not, at least not at first. One acid used consistently beats two used cautiously, and layering them is a common route to a compromised skin barrier. If you have both congestion and dullness, alternate nights once your skin is comfortable with each on its own.

Which acid is best for sensitive skin?

Lactic acid or a low-percentage salicylic is generally gentler. Glycolic acid is the most potent common AHA because its molecule is smallest and penetrates furthest, which makes it both effective and the most likely to sting. Patch test, start every other day, and speak to a dermatologist if irritation persists.

AHA vs. BHA: Which One You Need

Chemical exfoliants get sorted into two families, and the difference between them is not strength. It is where they can physically go.

Get that one distinction right and the rest of the decision follows almost automatically.

The actual difference

AHAs are water-soluble. They work on the surface of the skin, loosening the bonds between dead cells so they shed more evenly. The common ones are glycolic acid and lactic acid.

BHAs are oil-soluble. That means they can dissolve into sebum, so they get down inside a pore rather than working across the top of it. Salicylic acid is the one you will meet.

That is the whole mechanism. Surface versus inside the pore.

Which one your skin wants

Choose a BHA if the problem is congestion. Blackheads, clogged pores, bumpy texture, oily skin, breakouts. Being oil-soluble is precisely what lets it work where the clog is.

Choose an AHA if the problem is the surface. Dullness, uneven tone, rough texture, sun damage, fine lines. AHAs also act as humectants, meaning they draw in moisture, which is why they suit drier skin better than BHAs do.

If your skin is sensitive, lactic acid or a low-percentage salicylic is generally the gentler entry point. Glycolic is the most potent of the common AHAs because its molecule is the smallest and it penetrates furthest, which is exactly what makes it effective and exactly what makes it sting.

The strengths that matter

BHA leave-on products max out at 2% under FDA limits, so a 2% salicylic product is at the ceiling rather than being unusually strong. That is worth knowing because the number looks small next to AHA percentages and is not comparable to them.

AHAs in consumer products typically run 10 to 15%. Higher exists, mostly in professional settings, and is not a home decision.

So a 2% BHA and a 10% AHA are not two points apart in strength. They are different scales entirely, and comparing the numbers directly is the most common mistake people make in the aisle.

How to start either one

Every other day at most, and less if your skin objects. Frequency causes more trouble than concentration for most people.

One acid at a time. Layering an AHA and a BHA, or either with retinol, is how a good routine turns into a compromised barrier. If you want retinol in the routine too, alternate nights rather than stacking.

Sunscreen, without negotiation. Exfoliation makes skin more sun-sensitive, and skipping SPF undoes the point of the exfoliant. Our SPF picks are here.

Expect a settling-in period, not a transformation week. If you get small uniform bumps in the places you normally break out, that is probably purging and it has a timeline. If you get stinging, tightness or new spots somewhere you never break out, that is irritation and you should stop.

Do you need both?

Most people do not. One acid, used consistently, at a frequency your skin tolerates, does more than two used nervously.

If you genuinely have both concerns, congestion in the T-zone and dullness elsewhere, using a BHA and an AHA on separate nights is reasonable once your skin is well established with each individually. It is not a starting position.

For the pick at each strength, the exfoliant settle has it, and Paula’s Choice at 2% salicylic is the reference point most people start from.

Frequently asked

What is the difference between AHA and BHA?: Solubility, which decides where they work. AHAs are water-soluble and exfoliate the skin surface. BHAs are oil-soluble, so they dissolve into sebum and work inside the pore. That makes BHA the choice for congestion and AHA the choice for surface texture and tone.
Is 2% BHA strong?: It is the maximum for leave-on products under FDA limits, so it is at the ceiling rather than a low dose. The number is not comparable to AHA percentages, which commonly run 10 to 15 percent in consumer products. Different acids, different scales.
Can you use AHA and BHA together?: Most people should not, at least not at first. One acid used consistently beats two used cautiously, and layering them is a common route to a compromised skin barrier. If you have both congestion and dullness, alternate nights once your skin is comfortable with each on its own.
Which acid is best for sensitive skin?: Lactic acid or a low-percentage salicylic is generally gentler. Glycolic acid is the most potent common AHA because its molecule is smallest and penetrates furthest, which makes it both effective and the most likely to sting. Patch test, start every other day, and speak to a dermatologist if irritation persists.