✓ Glycolic acid verified
Nip + Fab Glycolic Fix Night Pads Extreme
Glycolic acid: 5% (+ salicylic + lactic + mandelic + hyaluronic acid)
Glycolic Acid vs Mandelic Acid: What the Studies Show
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Glycolic acid and mandelic acid are both alpha hydroxy acids, but they differ in size: glycolic acid weighs 76.05 g/mol and mandelic acid 152.15 g/mol, about twice as much. The size gap is a fact. Whether it makes mandelic acid gentler is a claim, and the evidence for it is narrow: a 2010 study found 10% glycolic acid exfoliated faster, reddened skin more and raised UV sensitivity more than mandelic acid. We found no study comparing consumer products, and many of the clinical trials test peels that combine mandelic acid with salicylic acid.
This page separates what each source measured from what comparison articles assume. Where a statement is our reading, it says so.
Glycolic Acid vs Mandelic Acid at a Glance
| Factor | Glycolic Acid | Mandelic Acid |
|---|---|---|
| Molecular weight | 76.05 g/mol, the smallest AHA (PubChem) | 152.15 g/mol (PubChem); an aromatic AHA with a phenyl ring |
| Penetration | Can penetrate deeper than other AHAs (Cleveland Clinic) | Not measured in any source we read |
| Exfoliation speed and redness | Faster exfoliation and more intense redness at 10% (2010 study, abstract) | Slower, described by the authors as safer, in the same study |
| Sun sensitivity | Higher photosensitizing effect than mandelic acid in the 2010 study; FDA study tested 10% (Kaidbey 2003) | Lower than glycolic acid in the 2010 study; the FDA's AHA warning covers any AHA by its wording |
| Consumer strength limit | The FDA reports the Cosmetic Ingredient Review panel found glycolic and lactic acid safe for consumers at 10% or less with a final pH of 3.5 or higher. The page does not name mandelic acid, so we found no equivalent ceiling for it. | |
| Studied for | Acne, melasma and keratosis pilaris in clinic peels (Cochrane, 2016, 2021) | Acne, dark circles and melasma in clinic peels at 10% to 45% (2020, 2025, 2016) |
| Rosacea | Cleveland Clinic lists rosacea among conditions needing caution | No study read |
What Is Glycolic Acid?
Glycolic acid is the smallest alpha hydroxy acid. Cleveland Clinic says it loosens the connection that holds dead skin cells together, can penetrate skin more easily than other acids, and advises starting once or twice a week. The FDA says how much an AHA exfoliates depends on its type and concentration, its pH and the other ingredients, so the percentage on a label is only part of the picture. Our percentage guide covers how strength is read.
What Is Mandelic Acid?
PubChem classes mandelic acid as an aromatic alpha hydroxy acid and notes it as an ingredient in topical cosmetic and drug products. The word aromatic here means a benzene ring in the molecule, which is part of why it weighs about twice as much as glycolic acid. A 2020 acne trial says it was studied for its antibacterial and anti-inflammatory properties; that is the authors' rationale for testing it, and the trial does not isolate those properties as the cause of any result.
Most of what is published on mandelic acid on skin concerns professional peels, often with salicylic acid in the same solution, so a result for a salicylic-mandelic peel is not a result for mandelic acid alone. In a 2018 study of 24 adults, a topical mandelic acid formulation applied twice a day for four weeks increased lower-eyelid skin elasticity by 25.4% and firmness by 23.8%, and the authors describe it as well tolerated; the abstract describes no comparison group, and the authors developed the formulation.
Is Mandelic Acid Gentler Than Glycolic Acid?
The honest answer is: in one study, yes; beyond that, not established. Here is what we read, and what each study can and cannot show:
- Glycolic vs mandelic, healthy skin (Rizza 2010). Researchers compared glycolic acid, mandelic acid and a grape juice acid mixture for how fast each exfoliated, how red skin became, and how much UV sensitivity rose. Glycolic acid at 10% w/w was faster, redder and more photosensitizing, and the authors describe mandelic acid as a slower and safer peeling action. We read the abstract only; it does not state the mandelic acid concentration, the number of participants or whether concentrations were matched, and we found no replication.
- Glycolic vs salicylic-mandelic peel, melasma (Sarkar 2016). In 90 Indian patients, a 35% glycolic acid peel and a peel of 20% salicylic acid with 10% mandelic acid cut pigmentation scores by about the same amount (62% and 61%). The authors say the salicylic-mandelic peel was better tolerated. Mandelic acid was one ingredient of three there, and all patients were primed with hydroquinone and tretinoin first.
- Glycolic vs salicylic-mandelic peel, acne (Cochrane 2020). There may be no difference in treatment response (one study, 40 participants, low-quality evidence), and the review is uncertain about minor adverse events because the evidence is very low quality.
- Mandelic vs lactic acid, dark circles (Malviya 2025). This trial of 70 people compared 30% mandelic acid with 30% lactic acid, not glycolic acid. Both improved pigmentation, lactic acid improved it more, irritation was more frequent with mandelic acid, and the authors say lactic acid may be better for sensitive skin. It is a warning against assuming mandelic acid is the gentlest AHA.
Put together, our reading is that mandelic acid looks milder than glycolic acid in the conditions tested, and is not shown to be milder than lactic acid. That is an inference from a few small studies, not a ranking any source gives.
Mandelic or Glycolic Acid for Sensitive Skin?
Cleveland Clinic lists sensitive skin, dry skin, rosacea, eczema and an active skin infection among the situations where glycolic acid calls for caution. Its facial-acids guide calls lactic acid one of the gentler AHAs and names azelaic acid, not mandelic acid, for redness and rosacea. That guide does not mention mandelic acid at all, and we found no study of mandelic acid in rosacea or in people who describe their skin as sensitive.
If you have sensitive skin, the sourced steps are the general ones: Cleveland Clinic advises testing on a small area first and starting slowly. See our sensitive skin guide for how glycolic acid fits in, and ask a dermatologist before using any acid on rosacea or eczema.
Mandelic or Glycolic Acid for Acne?
The head-to-head acne evidence is one study. The Cochrane review found that a glycolic acid peel and a salicylic-mandelic acid peel may not differ in treatment response, from 40 participants and low-quality evidence. A 2020 trial of 50 people found a 45% mandelic acid peel about as effective as a 30% salicylic acid peel, with salicylic acid better on non-inflammatory lesions and mandelic acid on inflammatory ones, and fewer adverse effects with mandelic acid. Neither trial tests a home product, and neither tests mandelic acid against glycolic acid alone.
For acne scars, we found no mandelic acid trial; a 2017 review of peels in acne lists mandelic acid among peeling agents in use without assessing it. For dark marks left by acne, Davis and Callender say post-inflammatory hyperpigmentation tends to affect darker skin more often and more severely, and that treatment needs care to avoid irritation. Which acid to choose for blemishes is therefore a decision to make with a dermatologist, not one a ranking settles.
When Glycolic Acid Is the Reasonable Choice
None of the sources we read tells you when to choose one acid over the other, so this is our reading, labelled as such:
- You tolerate acids and want a defined consumer ceiling. The FDA reports that the Cosmetic Ingredient Review panel found glycolic acid safe for consumer products at 10% or less and a final pH of 3.5 or higher; we found no equivalent figure for mandelic acid.
- Your concern is keratosis pilaris. A 2021 trial tested glycolic acid for it, at clinic strength; we found no mandelic acid trial for keratosis pilaris.
When Mandelic Acid Is the Reasonable Choice
- Glycolic acid has irritated you. The 2010 study found a slower, less reddening profile for mandelic acid than for glycolic acid, a 2020 trial found its peel better tolerated than a salicylic acid peel, and the authors of a 2018 formulation study call it well tolerated. That is the case for trying it. It is not a guarantee, given the 2025 result against lactic acid.
- You are weighing a gentler AHA and lactic acid is also an option. See our glycolic acid vs lactic acid guide: the only mandelic-versus-lactic trial we found favoured lactic acid.
Important: The FDA recommends that any cosmetic containing an alpha hydroxy acid carry a sunburn alert covering use and the week afterwards (FDA). The page does not name mandelic acid, and the UV study it cites tested glycolic acid. We use SPF 30+ as our line, which Cleveland Clinic advises with glycolic acid. See glycolic acid and sun exposure.
Can You Use Mandelic and Glycolic Acid Together?
We found no study of using the two together. Cleveland Clinic advises avoiding other exfoliants (lactic and salicylic acids), retinol and vitamin C serums when you are first starting glycolic acid, because fewer active ingredients lets you isolate what causes a reaction, and warns that overdoing it can cause irritation, dryness and increased sensitivity. Mandelic acid is not named, but it is another exfoliating AHA, so applying the same advice is our reading rather than a sourced rule.
What the literature does show is mandelic acid paired with salicylic acid in supervised peels, and one formula that combines several acids. The sensible course, again our reading: add one acid at a time, give your skin time to show how it responds, and if you want both, alternate nights before trying them in one routine. See how to layer glycolic acid for order and spacing.
Which Is Better for Darker Skin?
No source we read shows that either acid is safer for darker skin. The sourced point is a warning: Davis and Callender say post-inflammatory hyperpigmentation affects darker skin more often and more severely, and that all treatments need caution to prevent irritation. The nearest evidence is a peel trial in Indian patients, Sarkar 2016, whose abstract does not give skin types; it found similar efficacy for glycolic acid and a salicylic-mandelic peel, and its authors judged the salicylic-mandelic peel better tolerated. We cannot separate the mandelic acid from the salicylic acid in that result.
Product Note: A Pad That Contains Both
The only catalogue product we carry that contains both acids is a pad, and it is not a clean test of either one.
The Nip + Fab US product page states 5% glycolic acid for this pad, and its ingredient list includes mandelic, salicylic and lactic acids, niacinamide and sodium hyaluronate. The page gives no percentage for the mandelic acid, so we cannot say how much of it is present, and because several acids are listed the free acid from the glycolic portion cannot be calculated. The brand's UK page gives 3.5%, so check the label on the pack you buy. Because it mixes acids, it is a poor way to find out which one your skin prefers.
If you would rather test glycolic acid by itself first, here is a lower-strength option:
✓ Glycolic acid verified
Good Molecules Glycolic Exfoliating Toner
Glycolic acid: 3.5%
Good Molecules lists a 3.5% glycolic acid concentration for this toner, which is half the strength of The Ordinary's 7% toner. We have not tested it and have no published pH for it, so the free acid cannot be calculated. If you want to try glycolic acid on its own first, a lower label strength is a cautious start; introduce it alone, as Cleveland Clinic advises, once or twice a week to start.
What We Could Not Establish
We did not find a source for the claims that mandelic acid is suited to every skin type, that it is safe for rosacea, that it fades acne scars, or that it is the best AHA for sensitive skin, so this page does not make them. The strength comparison rests on a single abstract. A dermatologist who knows your skin is the right person to choose between these acids; this page cannot.
Frequently Asked Questions
Which is stronger, and which is gentler?
Glycolic acid is the stronger exfoliant in the one study we found that tested the two acids on their own, and mandelic acid was the gentler. In a 2010 in vivo study from the University of Catania, 10% glycolic acid produced faster exfoliation, more intense redness and a higher photosensitizing effect than the mandelic acid and grape juice acid mixtures, which the authors describe as a slower and safer peeling action. We read the abstract only; it does not give the mandelic acid concentration or the number of participants. Size points the same way: mandelic acid's molecular weight is 152.15 g/mol, about double glycolic acid's 76.05 g/mol, and Cleveland Clinic says glycolic acid's small size lets it penetrate deeper than other AHAs. We found no comparison of leave-on or rinse-off consumer products, so treat the gap as a reason to expect a difference, not a measured one.
Which suits sensitive skin or rosacea?
No source we read tests mandelic acid in rosacea, so we cannot say it suits it. Cleveland Clinic lists sensitive skin and rosacea among the conditions where glycolic acid calls for caution. For mandelic acid the evidence is about irritation in peels: a 2020 trial of 50 people with acne found fewer adverse effects with a 45% mandelic acid peel than with a 30% salicylic acid peel, while a 2025 trial of 70 people found irritation was more frequent with a 30% mandelic acid peel than with a 30% lactic acid peel, and its authors say lactic acid may be better for sensitive skin. So mandelic acid is not shown to be the mildest option. For redness and rosacea, Cleveland Clinic names azelaic acid, not mandelic acid. See our sensitive skin guide.
Which is better for acne, acne scars or dark spots?
It depends on the condition, and for each one the evidence is thin. Acne: the 2020 Cochrane review found there may be no difference in treatment response between a glycolic acid peel and a salicylic-mandelic acid peel (one study, 40 participants, low-quality evidence), and a 2020 trial found 45% mandelic acid and 30% salicylic acid peels about equally effective. Acne scars: we found no trial of mandelic acid for scars, and a 2017 review of peels lists mandelic acid only among the agents in use. Dark spots: in a 2016 melasma trial of 90 people, a 35% glycolic acid peel and a salicylic-mandelic peel reduced pigmentation scores by similar amounts. All of these were clinic peels, not home products, and in two of the three the mandelic acid was combined with salicylic acid.
Can you use them together, and what shouldn't you mix?
We found no study of using glycolic and mandelic acid together. Cleveland Clinic advises that when you are first starting glycolic acid you may want to avoid other exfoliants (it names lactic and salicylic acids), retinol and vitamin C serums, so you can isolate what causes a reaction, and warns that overdoing it can cause irritation, dryness and increased sensitivity. It does not name mandelic acid; applying its advice to mandelic acid is our reading, since mandelic acid is also an exfoliating AHA. Some products already combine them: the Nip + Fab Glycolic Fix Night Pads Extreme list both in one formula, with glycolic acid stated at 5%. If you want to try both, introducing one new acid at a time is the cautious route, and anything beyond that is untested.
What's the difference between mandelic acid and other AHAs?
The documented differences are chemical. PubChem describes mandelic acid as an aromatic alpha hydroxy acid, meaning it carries a phenyl (benzene) ring, and gives its molecular weight as 152.15 g/mol, against 76.05 for glycolic acid and 90.08 for lactic acid. The authors of a 2020 acne trial say they studied it for its antibacterial and anti-inflammatory properties, which is their stated rationale, not a result. What that size and structure change in everyday products has not been measured in anything we read.
What are mandelic acid peels used for?
In the studies we read, mandelic acid peels were clinic treatments for acne, pigmentation and thickened dark skin. Strengths and schedules in those studies: 45% every 2 weeks for six sessions for mild-to-moderate acne; 30% in three sessions over 4 weeks for dark circles around the eyes; and a peel pairing 10% mandelic acid with 20% salicylic acid for melasma. A salicylic-mandelic peel was also used for thickened, darkened underarm skin (acanthosis nigricans), with strengths not given in the abstract. A 2017 review lists mandelic acid among the peeling agents used in acne. In our reading those strengths belong to supervised treatment and are not a guide to what a home product at a lower strength will do; we found no study that tests a home mandelic acid product.
Which suits darker skin tones?
No source we read shows either acid is safer for darker skin. Davis and Callender say post-inflammatory hyperpigmentation tends to affect darker skin more often and more severely, and that every treatment needs caution to prevent irritation and worsening. The nearest evidence is a peel trial in Indian patients (the abstract gives no skin types): in a melasma trial of 90 people, 35% glycolic acid and a salicylic-mandelic peel were about equally effective, and the authors concluded the salicylic-mandelic peel was better tolerated and more suitable for Indian skin. That is the authors' conclusion about a combination peel in which mandelic acid was one ingredient, not a finding about mandelic acid alone. Whichever acid you choose, patch testing, a low starting strength and daily sun protection are the sensible reading of that warning.
Does mandelic acid raise sun sensitivity?
Probably, and treat it that way. The FDA recommends a sunburn alert on any cosmetic containing an alpha hydroxy acid, covering use of the product and the week afterwards; the page does not name mandelic acid, and the UV study it cites (Kaidbey 2003) tested glycolic acid. In the 2010 comparison, glycolic acid had a higher photosensitizing effect than mandelic acid, but that study does not show mandelic acid has none. Our house line is a broad-spectrum SPF 30 or higher, which Cleveland Clinic advises with glycolic acid. See our sun exposure guide.
Why is there so little head-to-head evidence?
We cannot say why; we can say what the gap looks like. Only one study we found, the 2010 Catania comparison, tests mandelic acid against glycolic acid alone, and we read only its abstract. The rest set mandelic acid against a different acid (salicylic or lactic) or fold it into a salicylic-mandelic peel before comparing that peel with glycolic acid, as the 2020 Cochrane review reports. Those trials ran 40 to 90 people for weeks to a few months, and all were clinic peels, so none speaks to a product bought off the shelf. Our reading is that this is why many comparison articles lean on molecular size, which is a fact, to argue for gentleness, which is a claim.