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Lactic acid

Lactic acid in skincare: Exfoliant, humectant. What it does on skin, how strong the evidence behind the claim actually is, the concentrations in normal use, who reacts to it, and where it stands in pregnancy and sunlight. On a label it appears as Lactic Acid.

Exfoliating acidsExfoliant, humectantEvidence: Strong

On the label: Lactic Acid. Also called: AHA, alpha hydroxy acid.

This is an ingredient reference, not a diagnosis and not a treatment plan. It describes what substances are and what the published evidence supports; it does not tell you what your skin has or what to put on it. A rash that spreads, hurts, weeps, does not settle, or comes with feeling unwell is a reason to see a doctor or pharmacist, not to change serum.

What it is

An alpha hydroxy acid with a bigger molecule than glycolic acid, so it moves into the skin more slowly and generally stings less. It is also one of the substances skin makes itself: lactate is part of the natural moisturising factor, the mix of small water-binding molecules inside the outer cells. That dual identity is why it both exfoliates and hydrates, which most acids do not.

What it does on skin

Like other AHAs it loosens the dead surface layer so it sheds evenly. Unlike them it also raises the water content of that layer directly, because lactate holds water. On the body it is the standard answer for the rough, bumpy or scaly skin of the upper arms and shins, where a 10-12% lotion both softens the plugs and stops the skin drying back out between applications.

What the evidence is worth

Evidence: Strong

Body lotions in the 10-12% range have a long clinical record in dry, scaly and rough skin and this is the best-supported use. For pigment and fine lines the evidence is thinner than for glycolic acid, mostly because less of it has been done. As a gentler entry point for someone who cannot tolerate glycolic acid, the reasoning is sound and the tolerability difference is real.

How it is used

On the face, an evening serum or toner in the 5-10% range, a few nights a week. On the body, a 10-12% lotion daily is normal and works better than intermittent use. Apply body lotion to skin still damp from the shower, which is the single change that makes the biggest difference in a dry Nordic winter.

Typical concentration in normal use: 5-12%, higher in body lotions. That is a description of the market, not a recommendation, and it is not a dose.

Who reacts to it

Milder than glycolic acid for most people but still an acid: stinging on freshly shaved legs, on eczema patches or around the nostrils is common. It should not be used on cracked heels or fissured skin, where it will burn and delay healing.

Pregnancy and breastfeeding

Generally considered fine

Treated the same way as other topical AHAs: poorly absorbed, generally considered acceptable, and worth mentioning to your midwife anyway. Skin sensitivity often changes in pregnancy, so a product you tolerated before may sting now.

Sunlight

More sun-sensitive

Same as the other AHAs — increased ultraviolet sensitivity during use and for roughly a week after. On the body this matters less in winter but it matters a great deal on a summer holiday.

Rules and labelling

Covered by the same alpha hydroxy acid framework as glycolic acid: consumer concentrations and minimum pH are constrained, higher strengths are professional-use, and sun-protection wording is expected on the label.

What it goes with, and what it does not

Lactic acid and urea in the same body lotion is a genuinely good combination, because one exfoliates and both hold water. On the face, keep it away from a retinoid on the same night unless you already know you tolerate both.

One thing people get wrong

The myth is that lactic acid is made from milk, so a product containing it cannot be vegan. Cosmetic lactic acid is produced by fermenting plant sugars — beet, corn, cane — with bacteria, and the finished molecule is identical whatever it came from. The word "lactic" records where chemists first found it in the 18th century, not where the bottle on your shelf got it.

Sources: EU Cosmetics Regulation (EC) No 1223/2009 and its annexes, as published in the European Commission's CosIng database, for every statement about what is permitted, restricted or banned · opinions of the Scientific Committee on Consumer Safety (SCCS) and safety assessments of the Cosmetic Ingredient Review (CIR) for the concentration positions · standard dermatology reference material for mechanism, tolerability and contact-allergy patterns · checked 2026-09-06. Deep links are deliberately omitted where a stable public URL could not be confirmed.

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