Vitamin C Ester Brightening Serum is a powerful, multi-tasking formula targeting uneven skin tone and discoloration. This light and refreshing herbal-citrus vitamin C serum for face features Vitamin C Ester, a more potent and less irritating form of vitamin C. This serum promotes the appearance of collagen-rich skin by visibly smoothing, brightening and minimizing discoloration. Our potent and best Vitamin C serum also contains squalene and rosemary leaf extract to hydrate, visibly reduce fine lines and tighten the appearance of skin. Our recommendation for when to use Vitamin C serum is after cleansing and before your favorite Perricone MD moisturizer.