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Lactic acid

INCI: LACTIC ACID · also An alpha hydroxy acid (AHA)

An AHA that smooths skin, and makes it more sensitive to the sun.

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C3H6O390.08 g/mol
oxygencarbonhydrogen
3D shape from PubChem 612

How common

All products6.5%
In conditioners17%
In shower gels14%
In body lotions9.9%

967 of 14,784 products with a full ingredient list in Open Beauty Facts; No. 43 of all the names found on their labels.

What it is

  • An alpha hydroxy acid (AHA), also formed when sugar ferments.

    2 sourcesHide
    concluded that products containing the AHAs glycolic and lactic acid are safe for use by consumers if[1] US Food and Drug Administration · open source
    A normal intermediate in the fermentation (oxidation, metabolism) of sugar.[2] PubChem (US National Library of Medicine) · open source

Why it is in products

  • To exfoliate and smooth the skin (fine lines, texture, tone, pores), or simply to set the product’s pH.

    2 sourcesHide
    Products containing AHAs are marketed for a variety of purposes, such as smoothing fine lines and surface wrinkles, improving skin texture and tone, unblocking and cleansing pores, and improving skin condition in general.[1] US Food and Drug Administration · open source
    Sometimes AHAs are used in cosmetics for other purposes, such as to adjust the pH (the degree of acidity or alkalinity).[1] US Food and Drug Administration · open source

What it does

  • It makes the surface skin shed (exfoliation). How much depends on the acid, its concentration, the product’s pH and its other ingredients.

    Well establishedskinSourceHide
    AHA-containing products cause exfoliation, or shedding of the surface skin. The extent of exfoliation depends on the type and concentration of the AHA, its pH, and other ingredients in the product.[1] US Food and Drug Administration · open source

  • For very dry skin, in double-blind studies a 12% lactate lotion (a salt of lactic acid) worked better than a 5% lactic acid lotion, and its benefit lasted longer after stopping than a plain moisturiser’s.

    Good evidenceskin2 sourcesHide
    patients receiving 12% lactate lotion, compared with those treated with nonlactated emollient lotion, had had significantly greater reductions in the severity scores of xerosis[3] Study · 1983 · open source
    Results showed 12% ammonium lactate lotion was significantly more effective than 5% lactic acid lotion in reducing the severity of xerosis[4] Study · 1989 · open source

  • It may strengthen the skin barrier: in lab and skin tests, lactic acid (most of all its L form) raised the skin’s ceramide levels and improved barrier function.

    Some evidenceskin2 sourcesHide
    In vivo, lactic acid increased the levels of stratum corneum ceramides.[5] Study · 1996 · open source
    Significant improvements in barrier function and resistance to the appearance of skin xerosis were observed following L-lactic acid and D,L-lactic acid, but not following D-lactic acid treatment.[5] Study · 1996 · open source

Downsides and safety

  • Like other AHAs, it makes skin more sensitive to the sun. In FDA studies, four weeks of an AHA cream raised sensitivity to sunburn by 18%; the effect was gone a week after stopping. Use sun protection.

    Well established4 sourcesHide
    These studies confirmed previous industry studies indicating that applying AHAs to the skin results in increased UV sensitivity.[1] US Food and Drug Administration · open source
    After four weeks of AHA application, volunteers' sensitivity to skin reddening produced by UV increased by 18 percent.[1] US Food and Drug Administration · open source
    One week after the treatments were halted, researchers found no significant differences in UV sensitivity among the various skin sites.[1] US Food and Drug Administration · open source
    If you are using AHAs, it is advisable to use sun protection.[1] US Food and Drug Administration · open source

  • Strong products can hurt: the FDA received reports of burning, rashes, swelling and pigment changes, most often from strong “skin peelers”.

    Good evidence2 sourcesHide
    The reported adverse experiences included burning (45), dermatitis or rash (35), swelling (29), pigmentary changes (15)[1] US Food and Drug Administration · open source
    The more serious adverse reactions appear to occur most often with products that cause the greatest degree of exfoliation, such as "skin peelers."[1] US Food and Drug Administration · open source

Where it works

SurfaceOuter layer(stratum corneum)Living layer(epidermis)Dermis

In the skin’s outer layer, which it loosens and sheds.

Well establishedSourceHide
AHA-containing products cause exfoliation, or shedding of the surface skin.[1] US Food and Drug Administration · open source

Rules

European Union

  • No EU limit: it is not on the regulation’s lists of banned or restricted substances, preservatives or UV filters.

    How we checkedHide
    We searched Annexes II to VI of the EU regulation (consolidated text of 18 May 2026): no entry.open the list

United States

  • The FDA advises a “Sunburn Alert” on AHA products: use a sunscreen, protective clothing and less sun while using the product and for a week after.

    2 sourcesHide
    Sunburn Alert: This product contains an alpha hydroxy acid (AHA) that may increase your skin's sensitivity to the sun and particularly the possibility of sunburn.[1] US Food and Drug Administration · open source
    Use a sunscreen, wear protective clothing, and limit sun exposure while using this product and for a week afterwards.[1] US Food and Drug Administration · open source

  • The US expert panel considers it safe at up to 10% with a final pH of 3.5 or more, when the product guards against sun sensitivity or tells users to protect their skin daily; in salon products up to 30%, applied briefly by trained professionals.

    3 sourcesHide
    are safe for use in cosmetic products at concentrations less than or equal to 10%, at final formulation pH greater than or equal to 3.5, when formulated to avoid increasing sun sensitivity or when directions for use include the daily use of sun protection[2] PubChem (US National Library of Medicine) · open source
    These ingredients are safe for use in salon products at concentrations less than or equal to 30%[2] PubChem (US National Library of Medicine) · open source
    when applied by trained professionals[2] PubChem (US National Library of Medicine) · open source
About these studies

The ceramide and barrier findings come from Unilever researchers. The FDA notes that the US expert panel’s AHA conclusions rested on industry-sponsored studies, and calls the panel the industry’s self-regulatory body.

2 sourcesHide
Unilever Research, Edgewater Laboratory[5] Study · 1996 · open source
Based on industry-sponsored studies, the Cosmetic Ingredient Review (CIR) Expert Panel — the industry's self-regulatory body for reviewing the safety of cosmetic ingredients[1] US Food and Drug Administration · open source

Sources

  1. Alpha Hydroxy Acids | FDA US Food and Drug Administration
  2. PubChem: Lactic acid (CID 612), record description PubChem (US National Library of Medicine)PubChem (US National Library of Medicine)
  3. 12% lactate lotion for the treatment of xerosis. A double-blind clinical evaluation Dahl MV et al., Archives of dermatology, 1983Study
  4. Comparative efficacy of 12% ammonium lactate lotion and 5% lactic acid lotion in the treatment of moderate to severe xerosis Rogers RS et al., Journal of the American Academy of Dermatology, 1989Study
  5. Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function Rawlings AV et al., Archives of dermatological research, 1996StudyAuthors include staff of Unilever

Checked against these sources on 4 November 2026. Spot a mistake? Tell us.