The Ordinary Lactic Acid 5% + HA 2% 30ml
This formula has a pH of approximately 3.8, which matches the pKa of Lactic Acid, also 3.8. The pKa is crucial in acid formulations as it determines the acid's availability. When the pKa and pH are closely aligned, it creates an optimal balance between salt and acidity, allowing for effective exfoliation with the right delivery of the acid, making it suitable for daily use.