Lactic Acid (0.3%)
Lactic acid is an alpha-hydroxy acid (AHA) and the second most researched AHA after glycolic acid, with CAS number 50-21-5. It is naturally found in sour milk and functions as both an exfoliant and a humectant/moisturizer. Its larger molecular size compared to glycolic acid means it penetrates the skin less deeply, making it generally more gentle. It also serves a buffering role in formulations.
Lactic acid gently lifts dead skin cells to reveal fresher, smoother skin, and has strong moisturizing properties. At higher concentrations (10% and above) and appropriate pH (3–4), studies show it can improve skin firmness, thickness, and wrinkles affecting both the epidermal and dermal layers. The L-lactic acid isomer specifically demonstrates effective exfoliation with lower irritation potential compared to the D-isomer.
Increases photosensitivity — sunscreen use is strongly recommended when using AHA-containing products. Effectiveness is highly dependent on both concentration and pH; pH 3–4 is considered optimal for at-home use. At 0.3% concentration, exfoliant activity is minimal; higher concentrations (5–12%+) are needed for meaningful exfoliation and anti-aging effects. May cause stinging or burning, particularly at higher concentrations or lower pH values.
