Mandelic Acid 10% + HA offers superficial dermal peeling that is gentler than other alpha hydroxy acids. The molecular weight of mandelic acid is 152.1 daltons which is larger than other alpha hydroxy acids (glycolic acid is 76.0 daltons for example). This larger size allows mandelic acid to penetrate the skin more slowly which in turn makes it very gentle & suitable for all skin types. You don't need a concentration of more than 10% because then you would simply be achieving an indirect peeling strength that is more easily offered through lower percentages of glycolic acid. Contraindications: This formula should not be used on sensitive peeling or compromised skin. Please refer to additional sun protection note & other warnings in provided Directions. Note: While exfoliating acids can result in quick visible benefits we generally suggest the use of indirect forms of skin exfoliation in favour of direct forms such as this formula due to potential inflammation & sensitivity associated with acids. Please refer to NIOD's Non-Acid Acid Precursor for such a suggested formula.