Lactic Acid 5% + HA is a mild alpha hydroxy acid solution that offers gentle yet effective exfoliation targeted at the skin's surface. It is supported with purified Tasmanian pepperberry extract, which has been shown to reduce irritation and sensitivity that can be associated with acid use. This water-based serum is ideal for dry and sensitive skin. The pH of this formula is approximately 3.8. Lactic Acid has a pKa of 3.8 and pKa is the most important aspect to consider in formulating with acids. pKa implies acid availability. When pKa is close to pH, there is an ideal balance between salt and acidity, maximising effectiveness of the acid and reducing irritation. Formulated to provide mild exfoliation, the Lactic Acid 5% + HA 2% Superficial Peeling Formulation from The Ordinary promotes a smoother, more evenly-toned complexion. The serum is fortified lactic acid, an exfoliating alpha hydroxy acid (AHA), to help improve the appearance of pigmentation, uneven skin tone and texture. The addition of a Tasmanian pepperberry derivative helps to soothe sensitive skin, while hyaluronic acid attracts and retains moisture. 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.