✓ Glycolic acid verified
The Ordinary Glycolic Acid 7% Exfoliating Toner
Glycolic acid: 7%
Glycolic Acid vs Lactic Acid: Which Is Right for You?
We independently evaluate products — verifying the ingredient list for every pick, and never accepting paid placement. Amazon links earn us a commission at no cost to you.
How we research · Affiliate disclosure →
Glycolic acid and lactic acid are both alpha hydroxy acids. They both exfoliate. They both show up in "best AHA" product lists. So what's actually different?
The difference most comparisons lead with is molecular size. Glycolic acid is the smallest AHA, at 76.05 g/mol, and Cleveland Clinic says that small size lets it penetrate skin deeper than other AHAs. Lactic acid is slightly larger, at 90.08 g/mol, about 18% heavier by simple division. What that size gap changes in practice is less settled than most comparison articles suggest: the two acids do several of the same things in lab and tissue studies, and we found no study that compares their depth or irritation head-to-head.
Glycolic Acid vs Lactic Acid at a Glance
| Factor | Glycolic Acid | Lactic Acid |
|---|---|---|
| Source | Sugarcane (Cleveland Clinic) | Milk and pickled vegetables (DermNet NZ); most lactic acid is made by fermenting cornstarch or beet sugar (Medical News Today) |
| Molecular weight | 76.05 g/mol (smallest AHA) | 90.08 g/mol |
| Penetration depth | Can penetrate deeper than other AHAs (Cleveland Clinic) | Not compared with glycolic acid in any source we read |
| Exfoliation intensity | No source ranks them. The FDA says it depends on the AHA's type and concentration, its pH and the other ingredients. | |
| Hydration | Exfoliating in general can be drying (AAD) | Lactic acid raised skin ceramides and barrier function in a 1996 Unilever-authored study; Medical News Today says it helps moisturize |
| Studied for | Keratosis pilaris at clinic strength (2021 trial); pigmentation, texture and clogged pores (Cleveland Clinic) | Firmness and lines at 12% (Smith 1996); dark spots and pores (FDA benefits listed by Medical News Today) |
| Irritation risk | Cleveland Clinic advises caution with sensitive skin; Medical News Today reports the AAD saying glycolic acid normally causes temporary irritation, especially in sensitive skin | Higher concentrations are more likely to irritate (Medical News Today). No source compares the two directly. |
| Sun sensitivity | The FDA says AHAs as a class may increase sun sensitivity. The UV study it cites (Kaidbey 2003) tested 10% glycolic acid on 29 people, and sensitivity returned to normal within a week of stopping. We found no equivalent lactic acid study, so we do not rank the two. | |
| Concentrations | FDA/CIR: safe for consumers at 10% or less with pH 3.5 or higher; professional peels 20–70% (DermNet NZ) | Home products usually 10% or less; superficial peels 10–30% (Medical News Today) |
| Results timeline | No comparable timeline in any source we read; Cleveland Clinic says over-the-counter products can take several months for pigmentation | Smith measured results after 3 months of twice-daily use; the lines-and-wrinkle effect was seen at 12% |
What Is Glycolic Acid?
Glycolic acid is an alpha hydroxy acid that Cleveland Clinic says comes from sugarcane. It is the smallest AHA, and Cleveland Clinic says that size lets it penetrate skin more easily than other acids.
Cleveland Clinic says it helps loosen the connection that holds dead skin cells together on the surface of the skin, and DermNet NZ describes AHAs as loosening the glue-like substances between surface cells so dead skin can peel off gently. Cleveland Clinic also lists collagen stimulation and a brighter, more even tone among its effects, and a 2006 study in Japanese volunteers found collagen I and procollagen I increased in the upper dermis after daily glycolic acid for 6 weeks. Medical News Today says it can inhibit bacterial growth at certain concentrations. For a full breakdown of how different concentrations work, see our percentage guide.
What Is Lactic Acid?
Lactic acid is another alpha hydroxy acid. DermNet NZ says it comes from milk and pickled vegetables, and Medical News Today says most lactic acid is produced by fermenting cornstarch or beet sugar, so some products suit vegans.
Its molecular weight is 90.08 g/mol, about 18% above glycolic acid's 76.05 by simple division. Whether that makes it gentler is not something we could source: no study we read compares the two acids' irritation or penetration directly.
On moisture, a 1996 study by Unilever researchers found lactic acid increased ceramide production by skin cells in culture, raised ceramide levels in the outer skin layer in volunteers using lactic acid lotions, and improved barrier function and resistance to dryness. Medical News Today says lactic acid helps moisturize the skin. We found no source that tests whether glycolic acid depletes moisture; the AAD says only that exfoliating in general can be drying.
Lactic acid is not unique in affecting pigment. A 2003 study of melanoma cells found glycolic acid and lactic acid both inhibited melanin formation, in a similar dose-dependent way, by directly inhibiting tyrosinase, and the effect did not depend on their acidity. In a 6-week study in Japanese volunteers, melanin was less prominent in skin treated daily with glycolic or lactic acid than with citric or acetic acid.
When to Use Glycolic Acid Instead of Lactic Acid
No source we read tells you when to choose one over the other. What follows is what the evidence supports, with our own reading labelled:
- Keratosis pilaris and underarm darkening, at clinic strength — glycolic acid has trial data in both: a 2021 KP trial used 50% or 70% glycolic acid, and a 2025 review of underarm hyperpigmentation found small glycolic acid studies. We found no lactic acid equivalent, and neither tested a home product.
- Pigmentation and fine lines — glycolic acid has evidence here, but so does lactic acid. Both cut tyrosinase activity in cells, and both raised collagen I in the 6-week study above. Nothing we read shows glycolic acid does it faster or better.
- You tolerate acids well and have stopped seeing results from a gentler product — this is our reading, not a sourced rule. If you are considering a step up, raise it with a dermatologist, and follow Cleveland Clinic's advice to start glycolic acid once or twice a week.
Important: The FDA says AHAs as a class may increase your skin's sensitivity to the sun, and the study it cites tested 10% glycolic acid (Kaidbey 2003). Cleveland Clinic advises broad-spectrum sunscreen of SPF 30 or higher, reapplied every two hours. We do not rank the two acids on sun sensitivity because no source we read does.
When to Use Lactic Acid Instead of Glycolic Acid
The same caveat applies: no source compares the two for these situations, so the reasoning below is ours except where cited.
- Sensitive or reactive skin — Cleveland Clinic advises caution with glycolic acid if you have sensitive skin, dry skin, rosacea or eczema. Medical News Today says higher lactic acid concentrations are more likely to irritate and recommends a patch test and a lower starting strength, so lactic acid is not free of the risk. Our reading is that a low-strength lactic acid product is a reasonable cautious start; that is not a finding.
- Dry or dehydrated skin — a 1996 study by Unilever researchers found lactic acid lotions raised skin ceramide levels and improved resistance to dryness, which is the evidence behind lactic acid's moisturizing reputation. We found no equivalent study of glycolic acid.
- Darker skin tones prone to hyperpigmentation — Davis and Callender say post-inflammatory hyperpigmentation tends to affect darker skin more often and more severely, and that all treatments need caution to prevent irritation. Neither acid is shown to be safer for this; choosing the gentler routine is the sensible reading of that warning.
- AHA beginners — Medical News Today recommends a patch test and a lower concentration before moving to stronger products. We do not give a build-up period, because no source we read does.
- Alternating with glycolic acid — some people rotate the two acids on different nights. That is our suggestion, not a tested regimen; see the next section.
Can You Use Both Glycolic Acid and Lactic Acid?
Probably, but not in the same routine while you are starting out. Cleveland Clinic says that when you are first starting out you may want to avoid using glycolic acid with other exfoliants such as lactic and salicylic acids, because reducing the number of actives helps you isolate what causes an issue if your skin reacts. We found no study of using the two together, so the options below are our suggestions, not tested regimens.
Alternating Days (Most Common)
Use glycolic acid on some nights and lactic acid on others, rather than layering them in one session. This is our suggestion; no source we read specifies how many nights of each.
Zoning (For Combination Skin)
If your T-zone is oily and congested but your cheeks are dry and sensitive, you can use glycolic acid on the oily areas and lactic acid on the drier areas. This is more work, but it addresses different needs on different parts of your face. It is our suggestion, not a tested approach.
Seasonal Rotation
Some people switch based on the season. This is a low-effort approach and an untested one; the point is to match strength to how your skin is behaving, not a calendar.
Important: Healthline lists these signs of over-exfoliation: irritation, burning or peeling, redness and inflammation, small breakouts, and new sensitivity to other products. It quotes a dermatologist advising you to stop exfoliating until your skin has healed, then restart about once a week, and suggests exfoliating no more than one to two times a week.
Products That Combine Both
Some formulas include glycolic and lactic acid together. We found no source on combined products, so follow the label and introduce them as a single new active. Some pads also add a third AHA, mandelic acid; our glycolic acid vs mandelic acid page sets out what is known about it.
Best Glycolic Acid Products to Start With
If you've read this comparison and decided glycolic acid is right for your skin, here are our recommended products — all verified to contain glycolic acid as a primary active ingredient.
Best glycolic acid toner for switching from lactic acid
The Ordinary's 7% toner is a reasonable starting point for someone moving from lactic acid to glycolic acid. Its 7% strength is under the 10% ceiling that the FDA reports the Cosmetic Ingredient Review panel concluded is safe for consumer products. We have not tested it, and we found no source on how quickly it works, so we make no timeline claim. Cleveland Clinic advises starting once or twice a week, and alternating with a lactic acid product on other nights is our suggestion rather than a tested routine.
Best glycolic acid toner for alternating with lactic acid
✓ Glycolic acid verified
Good Molecules Glycolic Exfoliating Toner
Glycolic acid: 3.5%
Good Molecules lists a 3.5% glycolic acid concentration, half the strength of The Ordinary's 7% toner. If you have been using lactic acid and want to try glycolic acid at a lower strength, that makes it a lower-strength option. It also suits the alternating-night idea above, which is our suggestion and untested.
Best glycolic acid cleanser to pair with a lactic acid leave-on
✓ Glycolic acid verified
L'Oreal Paris Revitalift 3.5% Pure Glycolic Acid Brightening Cleanser
Glycolic acid: 3.5%
A cleanser is a lower-commitment way to try glycolic acid. Medical News Today says leave-on formulas give the acid more time to work, so our reading is that a rinse-off formula exposes skin to it for less time, though we found no study measuring that. L'Oréal's cleanser lists 3.5% glycolic acid. If you keep using lactic acid as your leave-on treatment and add glycolic acid in the cleansing step, introduce one change at a time.
The Molecular Size Factor: What We Know and What We Don't
Most comparison articles focus on concentration, such as "use 10% glycolic acid for stronger results", and many claim molecular size matters more. The FDA frames it more broadly: the extent of exfoliation depends on the type and concentration of the AHA, its pH and the other ingredients in the product.
The sourced part about size is narrow: glycolic acid is the smallest AHA, and Cleveland Clinic says that lets it penetrate skin more easily and deeper than other AHAs. We did not find a source for the claims that lactic acid stays near the surface regardless of concentration, that glycolic acid stings because it reaches nerve endings, or that depth explains faster results and more irritation. Whether any concentration of lactic acid reaches as deep as glycolic acid has not been tested in anything we read.
On pH, the FDA reports that the Cosmetic Ingredient Review panel's conclusion covers products at 10% or less with a final pH of 3.5 or higher, and Medical News Today says most over-the-counter glycolic acid products have a pH around 4. We found no source that tests the claim that a well-formulated 10% lactic acid at pH 3.5 beats a poorly formulated 5% glycolic acid at pH 4.5. The practical point stands, which is the FDA's: read concentration, pH and format together rather than relying on the percentage on the label.
Frequently Asked Questions
Should I use glycolic acid or lactic acid?
No source we read compares the two head-to-head across skin types, so this is our reading of what is known. Cleveland Clinic calls glycolic acid the smallest AHA, says it can penetrate deeper than other AHAs, and advises caution if you have sensitive skin, dry skin, rosacea, eczema or an active skin infection. Medical News Today describes lactic acid as helping to moisturize as well as exfoliate and says home products are usually 10% or less. In the lab the two behave alike in some ways, including suppressing melanin formation. Our reading, not a sourced ranking: if you are new to exfoliation or your skin is dry or reactive, starting with lactic acid is a reasonable cautious choice, and moving to glycolic acid later is a decision for your skin's response, not a fixed timetable.
Which is stronger, 10% lactic acid or 7% glycolic acid?
No source we read compares them. The FDA says the extent of exfoliation depends on the type and concentration of the AHA, its pH and the other ingredients, so a percentage on a label does not settle it. Glycolic acid's molecular weight is 76.05 g/mol and lactic acid's is 90.08 g/mol, and Cleveland Clinic says glycolic acid's small size lets it penetrate skin more easily than other acids. Whether that makes 7% glycolic acid stronger than 10% lactic acid has not been tested in anything we read, so treat the size argument as a reason to expect a difference, not as a result.
Which is better for KP, lactic acid or glycolic acid?
No source we read compares them for keratosis pilaris. DermNet NZ lists moisturizers containing urea, salicylic acid, lactic acid or alpha hydroxy acids among treatments, with no ranking and no cure. The one glycolic acid KP trial we read, a 2021 study of 25 people, used 50% or 70% glycolic acid applied in a clinic, and we found no equivalent lactic acid trial. The idea that KP plugs sit deeper in the follicle and that glycolic acid's smaller molecules reach them better is not something we could source. See our keratosis pilaris guide for products.
Does glycolic acid pull out blackheads?
Cleveland Clinic lists removing dead skin cells and cleaning out clogged pores among glycolic acid's effects, and says it prevents blackheads and breakouts. As an exfoliant it works on the dead-cell buildup rather than extracting a blackhead, which is our description of the mechanism. DermNet NZ says salicylic acid slows the shedding of cells inside follicles, preventing clogging, and helps break down blackheads and whiteheads. We found no study of using the two together, and Cleveland Clinic advises avoiding other exfoliants such as salicylic acid alongside glycolic acid when you are first starting out, so introduce one at a time and follow the label. We do not give a frequency for blackhead results because no source we read does.
Does lactic acid fade dark spots?
It may, and the lab evidence is the same for glycolic acid. In a 2003 study of mouse and human melanoma cells, glycolic acid and lactic acid inhibited melanin formation in a similar dose-dependent way by directly inhibiting tyrosinase, independent of their acidity. In a 2006 study in Japanese volunteers, melanin pigment was less prominent in skin treated daily for 6 weeks with glycolic or lactic acid than with citric or acetic acid. Medical News Today lists reducing dark spots among the benefits the FDA associates with lactic acid. That means the tyrosinase pathway is not special to lactic acid. We found no source that tests whether lactic acid is gentler or better suited to melanin-rich skin; what is documented is that post-inflammatory hyperpigmentation affects darker skin more often and more severely, and that any treatment needs care to avoid irritation.
What's better than glycolic acid?
It depends on the goal, and no source we read ranks these. For sensitive skin, no source compares lactic with glycolic acid; mandelic acid is a larger molecule (152.15 g/mol), but in a 2025 trial of 70 people comparing 30% mandelic and 30% lactic acid peels for dark circles, lactic acid did better and mandelic acid caused irritation more often, so "even gentler" is not supported. For acne, DermNet NZ describes salicylic acid as a keratolytic that slows cell shedding inside follicles. For fine lines, Cleveland Clinic says retinol increases collagen production, and that vitamin C can help lighten dark spots and reduce fine lines and wrinkles. The claim that glycolic acid is the best AHA for surface resurfacing is not one we could source.
What should you never mix with glycolic acid?
No source we read says never, but Cleveland Clinic advises that when you are first starting out you may want to avoid using glycolic acid with other exfoliants (lactic and salicylic acids), retinol and vitamin C serums, so you can tell what is causing a reaction. The AAD says retinol, retinoids and benzoyl peroxide can make skin more sensitive or peeling, and that exfoliating while using them may worsen dryness or cause breakouts. For retinol specifically, Cleveland Clinic says to consider alternating days or using glycolic acid in the morning and retinol at night. We found no source on benzoyl peroxide deactivating glycolic acid or on a morning-and-night split for vitamin C; see our glycolic acid vs vitamin C guide.
What cannot be paired with lactic acid?
Medical News Today says to avoid lactic acid on the same days as retinol and to alternate between them instead. Cleveland Clinic lists lactic acid among the other exfoliants to avoid combining with glycolic acid when first starting out, and the AAD says exfoliating while using retinoids, retinol or benzoyl peroxide may worsen dry skin or cause breakouts. We found no source for a vitamin C concentration threshold. Cleveland Clinic's reason for using fewer actives is that it lets you isolate the cause if your skin reacts.
What do Koreans use for hyperpigmentation?
No source we read surveys Korean routines, so we cannot say what is typical. What a 2010 review of post-inflammatory hyperpigmentation in skin of color documents are the ingredients the question usually points to: topical tyrosinase inhibitors including hydroquinone, azelaic acid, kojic acid, arbutin and certain licorice extracts, plus other depigmenting agents including ascorbic acid and niacinamide, with a warning to avoid irritation. For niacinamide, a 2002 study by Procter & Gamble researchers found it inhibited melanosome transfer in a cell model and decreased facial hyperpigmentation after 4 weeks. We found no source on pairing lactic acid with niacinamide.
Which is best for hyperpigmentation, glycolic acid or lactic acid?
No source we read ranks them. The lab and tissue evidence points to similar effects: both inhibited tyrosinase in a cell study, and both left less melanin in the basal and squamous layers in a 6-week study. The idea that glycolic acid works faster because it penetrates deeper is not something we could source. On irritation, Medical News Today says strong or irritating skin care products can cause hyperpigmentation, and Davis and Callender say post-inflammatory hyperpigmentation tends to affect darker skin more often and severely and that all treatments need caution to prevent irritation. That applies to any acid, not only glycolic acid.
Is lactic acid safer than glycolic acid?
We found no source that compares irritation rates directly, and the widely repeated "clinical data shows lower irritation" line has no source we could find. What is documented: Cleveland Clinic advises caution with glycolic acid if you have sensitive skin; Medical News Today says higher lactic acid concentrations are more likely to irritate and recommends a patch test and a lower starting strength, and says the AAD notes glycolic acid normally causes temporary irritation, particularly in sensitive skin. The FDA sun-sensitivity warning covers AHAs as a class. On hydration, a 1996 study by Unilever researchers found lactic acid increased ceramide production in cell culture and raised skin ceramide levels and barrier function in volunteers using lactic acid lotions. Whether lactic acid is safer than glycolic acid at equal strength has not been tested in anything we read.
Is lactic acid anti-aging?
It has some evidence. In Smith's 1996 study, people applied 5% or 12% lactic acid twice a day for 3 months; the 12% group had increased epidermal and dermal firmness and thickness and clinical improvement in smoothness and in lines and wrinkles, while 5% changed the surface and epidermis but not the dermis (we read the abstract only). In the 2006 study, collagen I and procollagen I rose in the upper dermis after daily glycolic, lactic or citric acid for 6 weeks. So the collagen finding is not specific to lactic acid. We found no source that ranks lactic acid against retinol or glycolic acid for aging, or that shows its results are slower or that it is among the best alternatives.