Obagi's Professional C 15% Serum with potent Vitamin C and 15% L-Ascorbic Acid is an impressive antioxidant treatment designed to protect skin cells against daily damage while dramatically boosting collagen production and correcting uneven tone at the surface. When used daily, this serum provides a high level of protection against environmental stressors and free radicals, shielding the skin from their effects and effectively minimising the early signs of ageing.