Lactic acid is an alpha hydroxy acid (AHA) found in body lotions, toners and peels. It smooths rough, dry skin and softens the look of fine lines. In a three-month study, 5% improved the surface, while 12% also firmed and thickened the deeper layer. Like other AHAs, it can raise sun sensitivity.
- Helps with
- rough dry skin, bumpy texture, fine lines, dullness
- Evidence
- Moderate. A three-month comparison of two strengths plus a controlled six-month AHA study; the trials are small.
- Typical strength
- 5% and 12% in the three-month study cited here
- Works well with
- moisturizer, daily sunscreen
- Be careful with
- unprotected sun exposure, other exfoliating acids on the same night
What does lactic acid do for skin?
Lactic acid is the acid people often pick for dry, rough skin: shins that look ashy, elbows and upper arms that feel like fine sandpaper, or a face that looks dull because flakes catch the light. It loosens the worn top layer so it sheds more evenly, which leaves skin smoother and softer to the touch.
Is 5% or 12% lactic acid better?
It depends on what you want. In a three-month study, people applied either 5% or 12% lactic acid twice a day. Both strengths made skin smoother and improved the look of lines and the outer layer. Only 12% also changed the deeper layer, making it firmer and thicker. The author’s summary: “12% lactic acid influences both the epidermis and the dermis.” In everyday terms, a lower-strength lotion is for texture, while a higher strength goes after firmness too.
A six-month forearm study points the same way: lotions with 25% glycolic, lactic or citric acid made treated skin about 25% thicker than the placebo side, with denser collagen.
Does lactic acid make you more sensitive to the sun?
Plan as if it does. A sun-sensitivity trial on AHAs opens by noting that “Several studies suggest that AHAs can increase the sensitivity of skin to ultraviolet (UV) light.” That trial then showed it directly with 10% glycolic acid, a close relative, and the effect wore off within a week of stopping. Use sunscreen on any area you treat with lactic acid.
How long until you notice a difference?
The firmer, thicker skin in the lactic acid study was measured after 3 months of twice-daily use.
How do you use lactic acid?
On the body, apply a lactic acid lotion after showering on rough areas; see how to exfoliate your body without irritation and, for small rough bumps on the legs, strawberry legs. On the face, use it in the evening and follow with moisturizer. It belongs to the same family as glycolic acid, so pick one rather than layering both.
Who should be careful with lactic acid?
If it stings, stop and let skin settle before trying again. Patch test first, and keep sunscreen on treated areas.
- Smith WP. Epidermal and dermal effects of topical lactic acid. J Am Acad Dermatol. 1996;35(3 Pt 1):388-91.
- Ditre CM, et al. Effects of alpha-hydroxy acids on photoaged skin: a pilot clinical, histologic, and ultrastructural study. J Am Acad Dermatol. 1996;34(2 Pt 1):187-95.
- Kaidbey K, et al. Topical glycolic acid enhances photodamage by ultraviolet light. Photodermatol Photoimmunol Photomed. 2003;19(1):21-7.
- Kornhauser A, Coelho SG, Hearing VJ. Applications of hydroxy acids: classification, mechanisms, and photoactivity. Clin Cosmet Investig Dermatol. 2010;3:135-42.
Editorial content, not medical advice.