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A chemical exfoliant works by dissolving the bonds between dead skin cells rather than scrubbing them off, and which acid you reach for should depend on your skin type more than which one is trending. The Ordinary’s Glycolic Acid 7% Toning Solution (an AHA) is the strongest and best suited to normal-to-dry skin dealing with dullness or uneven tone. Paula’s Choice 2% BHA Liquid Exfoliant is oil-soluble and gets into pores, making it the better choice for oily, acne-prone, or blackhead-prone skin. CosRX’s Good Night Soft Peeling Gel (a PHA) is the gentlest of the three and the one to reach for if you have sensitive or rosacea-prone skin that reacts to the other two.
At a Glance
Best for dullness and uneven tone: The Ordinary Glycolic Acid 7% Toning Solution — a water-soluble AHA that works on the skin’s surface. Best for oily or acne-prone skin: Paula’s Choice 2% BHA Liquid Exfoliant — oil-soluble, so it can get inside congested pores. Best for sensitive skin: CosRX Good Night Soft Peeling Gel — a PHA with a larger molecule size that exfoliates more gently.
What Actually Separates AHA, BHA, and PHA
The difference isn’t marketing — it’s molecular. AHAs like glycolic acid are water-soluble and work on the skin’s surface, which makes them effective for dullness and texture but means they can’t get inside a pore. BHAs like salicylic acid are oil-soluble, so they can penetrate into pores clogged with sebum, which is why dermatologists commonly recommend them for blackheads and acne. PHAs like gluconolactone have a larger molecular structure that exfoliates more slowly and gently, which is why they’re the go-to recommendation for rosacea-prone or reactive skin, according to overviews from dermatology-focused skincare resources.
AHA vs. BHA vs. PHA Chemical Exfoliants Compared
| Product | Acid Type | Size | Approx. Price | Best For | Typical Frequency |
|---|---|---|---|---|---|
| The Ordinary Glycolic Acid 7% Toning Solution | AHA (glycolic) | 240ml | ~$13 | Dullness, uneven tone, texture | Nightly |
| Paula’s Choice 2% BHA Liquid Exfoliant | BHA (salicylic) | 4oz / 118ml | ~$34–$36 | Oily skin, blackheads, acne-prone pores | Nightly |
| CosRX Good Night Soft Peeling Gel | PHA (gluconolactone) | 120ml | ~$18–$22 | Sensitive or rosacea-prone skin | 2–3x per week |
The Real Monthly Cost of Each Acid
Bottle price alone is misleading here, because these three products aren’t used the same number of times per month. The Ordinary’s toner is applied with a soaked cotton pad nightly, using roughly 2ml per application, which stretches a 240ml bottle to about 120 uses. Paula’s Choice BHA is a few drops applied directly nightly, using roughly 1ml per application from its 118ml bottle, for about 118 uses. CosRX’s PHA gel is recommended only 2–3 times a week rather than nightly because it doubles as a gentle peeling gel, so a 120ml bottle used at roughly 3ml per application across 2.5 uses per week lasts considerably longer in real time, even though it’s used less frequently per bottle.
| Product | Bottle Price | Uses Per Bottle | Cost Per Use | Approx. Monthly Cost |
|---|---|---|---|---|
| The Ordinary Glycolic Acid 7% | ~$13 | ~120 (nightly, ~4 months) | ~$0.11 | ~$3.25 |
| Paula’s Choice 2% BHA | ~$35 | ~118 (nightly, ~4 months) | ~$0.30 | ~$8.75 |
| CosRX PHA Gel | ~$20 | ~40 (2–3x/week, ~4 months) | ~$0.50 | ~$5 |
The takeaway: The Ordinary’s toner is the cheapest acid here by a wide margin per use, but Paula’s Choice BHA and CosRX’s PHA gel both land in a similar monthly range once you account for how often each is actually meant to be applied — the sticker price gap overstates the real difference.
Where Each Acid Wins — and Its Dealbreaker
The Ordinary’s Glycolic Acid 7% wins on value and surface-level brightening — it’s the cheapest per use and one of the most-repurchased toners in its category. Its dealbreaker: at 7% concentration in a toning solution, it can sting on already-irritated or very sensitive skin, and like all AHAs it increases sun sensitivity, so daily sunscreen isn’t optional while using it.
Paula’s Choice 2% BHA wins for anyone dealing with clogged pores or blackheads, since salicylic acid’s oil solubility is what lets it work inside the pore rather than just on the surface. Its dealbreaker: it’s the priciest of the three per bottle, and it isn’t the right tool for dullness or dry-skin texture concerns, since that’s an AHA’s job.
CosRX’s PHA gel wins on gentleness — it’s the acid most likely to be tolerated by rosacea-prone or reactive skin that can’t handle glycolic or salicylic acid. Its dealbreaker: it’s also the mildest exfoliant of the three, so it won’t deliver the same visible results for dullness or acne that the other two can.
How We Compared
This is general information, not a substitute for advice from a dermatologist, especially if you have a diagnosed skin condition like rosacea or eczema. This comparison draws on manufacturer product listings, ingredient concentration data, and general dermatology-education resources on how AHAs, BHAs, and PHAs differ. We did not personally test these products. Cost-per-use figures are estimates based on typical application amounts and frequency and will vary by individual use. Prices are approximate, current as of publication, and change frequently — confirm the latest price with the retailer before buying. See our editorial standards for more on how we research every comparison.
Frequently Asked Questions
Can I use AHA, BHA, and PHA together?
Most skincare routines only need one exfoliating acid at a time. Layering all three, or even two, increases the risk of irritation, redness, and a compromised skin barrier. If you want to try more than one, alternate them on different nights rather than applying them in the same routine.
Which acid is best for sensitive skin?
PHAs like the gluconolactone in CosRX’s Good Night Soft Peeling Gel are generally considered the gentlest option because their larger molecule size slows how quickly they exfoliate, making them the acid most commonly tolerated by sensitive or rosacea-prone skin.
Do chemical exfoliants increase sun sensitivity?
Yes, AHAs and BHAs both increase how easily skin sunburns, so daily broad-spectrum sunscreen is essential while using them. PHAs are generally considered lower-risk in this regard, but daily sunscreen is still good practice for any exfoliating routine.
How often should you use a chemical exfoliant?
This depends on the specific product and your skin’s tolerance. Some AHA and BHA formulas are labeled for nightly use, while gentler formulas or higher concentrations may only be recommended two to three times a week. Always follow the specific product’s instructions rather than assuming all exfoliants share the same schedule.
Building out the rest of your routine? See our comparisons of moisturizers, facial cleansers, and anti-aging actives, or browse our full skincare coverage.
