Receive a free Skinceuticals Vitamin C Antioxidant Serum Deluxe Sample in the mail. Vitamin C serum is an essential step in any SkinCeuticals skincare regimen. These synergistic, high-concentration antioxidants are designed for optimized absorption in skin and proven in peer-review research to help prevent free radical damage that can lead to the appearance of premature aging. Vitamin C for skin can also improve the look of fine lines, wrinkles, and discoloration.