Potassium Lactate

Potassium lactate is a humectant and buffering agent commonly used in leave-on products at low-to-moderate levels (often ~1–5%) and is generally well tolerated, even in sensitive skin. However, as a salt of lactic acid it can increase stinging on compromised barriers (eczema, post-procedure) and higher concentrations can be irritating due to osmotic effects and pH/ionic strength, so it is not fully inert. Given its overall good tolerability but real sting potential in reactive populations, a gentle-but-not-exceptional score is most consistent with patient-safety data. Safety Notes: In commercial skincare, potassium lactate is most often used as a minor pH adjuster/humectant at trace-to-low levels (~0.05–0.5%) in cleansers, toners, and emulsions, where the lactate function is supportive rather than a headline active. Higher levels are seen in strongly humectant, NMF-style body lotions/hand creams and some urea/lactate foot creams where lactate salts are used for moisturization and mild keratolytic support; consumer-available leave-on products are commonly 2–5% and can reach ~10–12% when formulated for very dry/rough skin with appropriate buffering (higher levels are limited mainly by tack, saltiness/irritation risk, and pH/stability constraints). No specific global maximum is universally set for potassium lactate in cosmetics (it is generally allowed), so observed limits are primarily practical/formulation-driven rather than regulatory.