In the case of Josie Maran Argan Bright Skin Vitamin C Serum ($65), the vitamin C is part of an argan oil-based serum, which means this brightening product glides on easily and quickly absorbs into your skin. The vitamin E in argan oil works to stabilise the vitamin C which helps it last longer and prevent free radicals from wreaking havoc for months to come. (Plus, 92 percent of the shoppers who've reviewed this serum, would recommend it to others.)