Lactic Acid

Lactic acid is a member of the alpha hydroxy acid (AHA) family of exfoliants. Alpha Hydroxy Acids are chemical exfoliants that work by loosening bonds between dead skin cells, promoting shedding of dead skin cells and revealing brighter, smoother skin. Lactic acid can improve skin texture, reduce the appearance of fine lines and wrinkles, help fade dark spots, and hydrate the skin. It also has antimicrobial and antioxidant properties, making it beneficial for acne-prone skin and potentially protecting against environmental damage. 

Lactic acid is gentler on the skin than it’s cousin Glycolic Acid because it’s a larger molecule, but when formulated at a pH below 4.0 it penetrates the skin and has been shown to increase ceramide production in the skin.

Studies have shown that lactic acid, particularly in higher concentrations (10%), can lead to increased epidermal and dermal thickness, improving skin firmness and reducing the appearance of wrinkles. 

Lactic acid can help fade dark spots and even out skin tone by promoting cell turnover and reducing melanin production. It’s also a humectant, meaning it attracts and retains moisture in the skin, contributing to improved hydration. In one study comparing Lactic Acid to Glycolic acid, after 22 weeks, treatment glycolic acid  and L-Lactic acid were equally effective on photo damage and sallowness but Lactic Acid was also effective on mottled hyperpigmentation and roughness.

In a study comparing 25% glycolic, lactic, or citric acid, treatment with AHAs caused an approximate 25% increase in skin thickness. The epidermis was thicker and papillary dermal changes included increased thickness, increased acid mucopolysaccharides, improved quality of elastic fibers, and increased density of collagen

Sources:

Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function. Arch Dermatol Res. 1996

Topical 8% glycolic acid and 8% L-lactic acid creams for the treatment of photodamaged skin. Arch Dermatol. 1996

Epidermal and dermal effects of topical lactic acid. J Am Acad Dermatol 1996

Alpha-hydroxyacids in the treatment of signs of photoaging. Clin Dermatol 1996

Comparative effectiveness of α‐hydroxy acids on skin properties. Int J Cosmet Sci 1996

Effects of alpha-hydroxy acids on photoaged skin: a pilot clinical, histologic, and ultrastructural study. J Am Acad Dermatol. 1996