Ingredient glossary
Lactic acid
On your shelf ✓What Lactic acid does for your skin, who it suits, and what to watch for.
INCI: Lactic Acid · Also: AHA
In short: Lactic acid delivers exfoliation and hydration, suits most skin types, and the evidence behind it is moderate. One thing to know: clear it with your doctor if pregnant; introduce it gently.
- What it does
- Exfoliation, hydration
- Best for
- Most skin types
- Watch out
- Clear it with your doctor if pregnant; introduce it gently
- Evidence
- Moderate
- How long
- 3 months+
how it was measured
Measured on investigator-graded photodamage severity (roughness, mottled hyperpigmentation, sallowness); measured at the trial's end, so possibly sooner.PMID 8651713PMID 8784274
The molecule
The Glow take
One of the ingredients I trust most.
When your goal is deep, lasting hydration, Lactic acid delivers, with a solid amount of evidence behind it. Introduce it gently, and pair it with something soothing if your skin runs sensitive.
— Maya
What it does
- exfoliation
- hydration
moderate evidenceSignificant evidence for AHA exfoliation, improving texture, tone and photoaging signs at appropriate pH and strength.
Why we say this
- CIR safety review 40th Anniversary Overview and Rereview Summaries From 2011 to 2015
- CIR safety review Final Report on the Safety Assessment of Glycolic Acid and related ingredients
The AHA family, at a glance
7 AHA entries in the base, Lactic acid among them. 5 of the 7 are a supporting active.
- Glycolic acid76 Da
- Lactic acid90 Da
- Ammonium lactate107 Da
- Malic Acid134 Da
- Tartaric Acid150 Da
- Mandelic Acid152 Da
- Citric Acid192 Da
How much do you need?
8%+
The vehicle-controlled trials worked from 8%; no published dose comparison sets a ceiling.
The trials, and what they used
- Floor 8%: The percentage of patients using either 8% glycolic acid or 8% L-lactic acid creams on the face achieving at least 1 grade of improvement (using a scale from 0 through 9) in overall severity of photodamage was significantly greater than with the vehicle cream (76% glycolic acid, 71% lactic acid, and 40% vehicle; P < .05).
The pH it needs
The un-ionised acid (pKa 3.86) is the active form; permeation through human epidermis fell step by step as gel pH rose from 2.8 to 3.8 to 4.8.
pH 5.0 is above 3.8, past the line the study drew (human epidermis).
The greater amount permeated at all time intervals (6 h, 9 h, 12 h, and 24 h) was obtained when the concentration of lactic acid was 9% and the pH of the gel formulation was 2.8.
Drag the handle along the line. Only what was measured is drawn; between the marks nothing was. Your skin's surface: about 4.7 at rest, 5.1 on a normal day.PMID 18489300PMID 14528393
Who it's for, and who should skip it
Tends to suit
- dry
- normal
- combo
Approach with care
- very sensitive
- compromised barrier
- Clogs poresLow
- Irritation riskModerate
- pH-dependentIts effect depends on the product's pH
How it fits each skin type
- DrySuits
- CombinationSuits
- OilySuits
- SensitiveTake care
Take extra care if any of these apply to you: compromised barrier.
Where it fits in your routine
Increases sun sensitivity while you are using it, so sunscreen matters more than usual.
Why we say this
- Alpha hydroxy acid: FDA recommends AHA cosmetics carry a sunburn alert and daily sunscreen direction, based on studies in which AHA-treated skin showed increased UV sensitivity that reversed roughly a week after stopping.
FDA guidance for industry on labelling cosmetics containing alpha hydroxy acids (sunburn alert); CIR AHA safety assessment
Give it three months or more, and possibly less: that is simply when it was measured.
What was measured, and in whom
- Measured on: investigator-graded photodamage severity (roughness, mottled hyperpigmentation, sallowness).
- The load-bearing trial is a 22-week double-blind vehicle-controlled study in 74 women applying 8% L-lactic acid cream twice daily, reporting at its endpoint: on the forearms at week 22 lactic acid beat vehicle on overall severity of photodamage, mottled hyperpigmentation, sallowness and roughness, and on the face 71% of the lactic group gained at least one grade of improvement in overall severity against 40% on vehicle.
- So 22 weeks is a ceiling and surface smoothing almost certainly starts much earlier.
- One correction to how this row is usually written: only that trial is vehicle-controlled.
- The supporting 5% and 12% lactic acid study over three months had no placebo arm — participants applied one strength or the other — so it corroborates the direction and supplies the histology, not the attribution.
- The hydration side of the ingredient is probably a days-scale effect, but the trials showing fast xerosis relief used 12% ammonium lactate, a different salt and a different row.
- The immediate slip felt after one application is a sensory impression, not an outcome.
Stiller MJ, Bartolone J, Stern R, Smith S, Kollias N, Gillies R, Drake LA. Topical 8% glycolic acid and 8% L-lactic acid creams for the treatment of photodamaged skin. A double-blind vehicle-controlled clinical trial. Arch Dermatol 1996;132(6):631-6. PMID:8651713 (74 women, 22 weeks). Uncontrolled corroboration: Smith WP. Epidermal and dermal effects of topical lactic acid. J Am Acad Dermatol 1996;35(3 Pt 1):388-91. PMID:8784274 (5% and 12% lactic acid, 3 months, no placebo arm).
Plays well with
- humectants
- ceramides
Lactic acid, answered
Is Lactic acid safe during pregnancy?
Clear it with your doctor first. Lactic acid is flagged as use-with-caution during pregnancy and breastfeeding, so check with your doctor or midwife before adding it.
Who should avoid Lactic acid?
Approach Lactic acid with care if any of these apply to you: very sensitive and compromised barrier. Its irritation risk is moderate, so introduce it slowly and patch test first.
What concentration of Lactic acid actually works?
Its concentration is rarely printed on the label, so use the ingredient list as your clue: near the top third it is likely doing real work, near the bottom it is more of a sprinkle.
During pregnancy
Treat Lactic acid as a maybe rather than a yes for now. It is flagged as one to use with caution while pregnant or breastfeeding, so it is worth clearing before you carry on.
When in doubt, check with your doctor or midwife. They outrank any website, including this one.When it is worth booking →
Commonly confused with
- Glycolic acidBoth are AHAs. Glycolic is the smaller molecule that gets in deeper and stronger; lactic is gentler and also hydrates.
On the map
See Lactic acid on the clash map →Compare Lactic acid with
11 comparisons built, the 5 most looked-up above.
Can you mix Lactic acid with
25 pairings built, the 5 most looked-up above.
This, for every label you own
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Sources & how we reviewed this
- CIR safety review 40th Anniversary Overview and Rereview Summaries From 2011 to 2015summary page only, the document itself was not read
- CIR safety review Final Report on the Safety Assessment of Glycolic Acid and related ingredientssummary page only, the document itself was not read
What changed on this page
- : the pH it needs
- : the effective dose from trials, the highest dose tested
- : what the EU regulates