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Exfoliating acids

Lactic acid (ammonium lactate)

Also listed as ammonium lactate, L-lactic acid

A gentler AHA that also draws in water. As a 12% ammonium lactate lotion it has good trial evidence for very dry, rough and scaly skin.

Moderate evidenceTypical strength: 5-12%

What it is

Lactic acid is an AHA slightly larger than glycolic acid and part of the skin's own natural moisturizing factor, so besides loosening dead cells it acts as a humectant. Ammonium lactate is lactic acid partly neutralized with ammonia; at 12% it is a long-standing treatment for severe dry skin (xerosis), rough bumpy skin on the arms and legs, and inherited scaling conditions.

It shows up mostly in body lotions and 'smoothing' creams for rough skin.

How strong is the evidence?

Moderate evidence

A double-blind trial found 12% ammonium lactate lotion outperformed 5% lactic acid lotion for moderate to severe dry skin, with benefits lasting through a 3-week break. An 8% L-lactic acid cream modestly improved photodamage, mottled pigment and roughness in a 22-week vehicle-controlled trial. The trials are older and moderate in size.

What it's used for, checked

Very dry, rough or scaly skin

Holds up

12% ammonium lactate beat 5% lactic acid for moderate to severe dryness over 3 weeks.

Bumpy upper arms (keratosis pilaris)

Mixed

Commonly recommended and softens the bumps; they usually return when you stop.

Sun damage and mottled tone

Holds up

8% L-lactic acid cream beat vehicle on photodamage and mottled pigment over 22 weeks.

Works well with

  • A thick moisturizer on very dry skin
  • Sunscreen on exposed areas

Who should be careful

  • Stings on cracked, freshly shaved or broken skin; apply to intact skin.
  • Like other AHAs it can increase sun sensitivity; use sunscreen on exposed areas.
  • Avoid on inflamed eczema.

The studies

Every citation is checked against its PubMed record.

  1. Comparative efficacy of 12% ammonium lactate lotion and 5% lactic acid lotion in the treatment of moderate to severe xerosis.
    Rogers RS 3rd, Callen J, Wehr R, Krochmal L · Journal of the American Academy of Dermatology · 1989 · RCT

    In a double-blind trial in moderate to severe dry skin, 12% ammonium lactate lotion twice daily reduced xerosis more than 5% lactic acid lotion over 3 weeks, and the advantage held through a 3-week no-treatment period.

  2. Topical 8% glycolic acid and 8% L-lactic acid creams for the treatment of photodamaged skin. A double-blind vehicle-controlled clinical trial.
    Stiller MJ, Bartolone J, Stern R, Smith S, Kollias N, Gillies R, et al. · Archives of Dermatology · 1996 · RCT

    74 women with photodamaged skin used 8% glycolic acid, 8% L-lactic acid or vehicle cream twice daily for 22 weeks; at least one grade of facial improvement was seen in 76%, 71% and 40% respectively. Lactic acid also improved mottled pigment and roughness on the forearms. Benefits were modest and the creams well tolerated.