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Lactic Acid

Depends on youExfoliantexfolianthumectantph-adjuster

Genuinely relevant for some people, or depends on dose and pH.

Also written as: AHA · Alpha Hydroxy Acid · 2-Hydroxypropanoic Acid

What it is

Lactic acid is an alpha hydroxy acid produced by fermentation (it is what makes milk sour) and is made industrially from sugars. Its molecule is larger than glycolic acid's, so it penetrates more slowly and generally stings less. It is also a humectant and part of skin's own natural moisturising factor, which is why it appears in masks aimed at dry, dull skin. Many products contain it purely as a pH adjuster at levels far too low to exfoliate.

What it does well

  • Exfoliates while also drawing water into the skin

    A controlled study found 5% lactic acid modified the skin surface and epidermis, while 12% also produced measurable changes in the dermis, alongside its well-known water-binding effect.

    Moderate evidence

  • Tends to feel milder than glycolic acid at the same strength

    The larger molecule penetrates more slowly, and the EU advisory committee set a higher recommended pH for lactic acid (5.0) than for glycolic acid (3.8), which also reduces sting. Head-to-head tolerability trials are limited.

    Limited evidence

Worth knowing

  • The AHA sun-sensitivity caution applies here too

    The EU advisory committee's UV findings covered alpha hydroxy acids as a class and recommended protecting skin from UV while using them. There is no EU-mandated warning text, but daily sunscreen is the sensible response.

    Matters most toAnyone using an exfoliating strength of lactic acid, particularly in summer.

  • Can sting on broken or over-exfoliated skin

    Discomfort is usually short-lived and dose- and pH-dependent; persistent burning or redness means the strength or frequency is too high.

    Matters most toPeople with a compromised barrier, eczema or active irritation.

Where the EU stands

No specific restriction

Not listed in Annexes II-VI of the EU Cosmetics Regulation, so there is no legal maximum. On precautionary grounds the Commission's advisory committee (SCCNFP) suggested lactic acid up to 2.5% at pH 5.0 or above for general consumer use, with warnings about eye contact and UV exposure. Products routinely exceed that advisory figure; safety is then the responsibility of the brand's safety assessor.

source ↗

Sources (2)

Every link goes to the original: a journal, a PubMed record or an EU document.

  1. [1]
    Position Paper concerning the Safety of alpha-Hydroxy Acids (SCCNFP/0370/00)

    SCCNFP, European Commission · 2000

    On the precautionary principle the committee suggested lactic acid may be used safely up to 2.5% at pH 5.0 or above, with consumer warnings about eye contact and UV protection.

  2. [2]
    Epidermal and dermal effects of topical lactic acid

    Journal of the American Academy of Dermatology · 1996 · doi:10.1016/s0190-9622(96)90602-7

    5% lactic acid altered the skin surface and epidermis while 12% also affected the dermis, showing that AHA benefits come from changes at several skin levels.

Masks that contain Lactic Acid