The Ordinary Lactic Acid 10 + HA - 1 fl oz - Ulta Beauty

"Lactic Acid is an alpha hydroxy acid (AHA) that offers superficial exfoliation to enhance smooth skin texture and radiance. This formula is supported by the addition of purified Tasmanian pepperberry extract to offer a comforting benefit to the skin in effort to reduce sensitivity that is associated with acid use. The formula is further supported with the inclusion of hyaluronic acid for multi-depth hydration. A milder 5% formula is available here. This pH of this formula is approximately 3.8 and Lactic Acid has a pKa of 3.8. The pKa value is the most important aspect to consider in formulating with acids as pKa implies acid availability. When pKa is close to pH, there is an ideal balance between salt and acidity, maximizing the efficacy of the acid and reducing the potential of developing irritation. Higher pH values in such a case would increase the concentration of salt, which counter-intuitively would make the formula even more irritating than if the formula was more acidic.Contraindications: Lactic Acid should not be used on sensitive, peeling or compromised skin. Please refer to additional sun protection note and other warnings in provided Directions. "