Discover Obagi's bestselling Professional C® Serum 20%. Our highest concentrated Vitamin C serum helps minimize the appearance of fine lines and wrinkles. Daily Use of Vitamin CProactively fortifies the skin defenses against environmental assaults. Encourages skin to rebound from previous, visible damage for an improved appearance of fine lines, wrinkles and uneven skin tone. Strengthens skin defense with a powerful antioxidant that helps skin appear younger for longer. Key Ingredients: Known as the purest form of Vitamin C, L-ascorbic Acid helps neutralize free radicals, minimize the look of fine lines and wrinkles, and brighten skin tone. Dermstore has partnered with Flex to allow you to use your Health Savings Account (HSA) or Flexible Spending Account (FSA). This means you can now use your HSA or FSA debit card to buy Obagi Medical products with pre-tax dollars, resulting in net savings of 30-40%, depending on your tax bracket. Eligible for HSA/FSA with a letter of medical necessity at checkout. From dermatologist-recommended treatments to solutions for chronic skin conditions like acne, eczema, and rosacea, these products are both effective and eligible. | Obagi Medical Professional-C Serum 20%, 0. 42 oz | Dermstore