Vitamins are organic substances (that just means they include the element carbon) that are essential for normal growth and nutrition, and are required in small quantities in the diet because they cannot be synthesized by the body. There are two types of vitamins: fat-soluble and water-soluble. Fat-soluble vitamins include A, D, E, and K. Water-soluble vitamins include all 8 B vitamins, as well as vitamin C and vitamin P (bioflavonoids). The most common vitamins used in skin care products include vitamins A, C, and E, niacinamide (vitamin B3), and panthenol (provitamin B5). The majority of vitamins function as antioxidants. Antioxidants limit oxidative damage caused by free radicals, the unstable molecules that contribute to the formation of premature wrinkles and fine lines on the skin. In addition to functioning as antioxidants, each vitamin provides unique skin care benefits. For example, vitamin C is well known to help fade dark spots and brighten the complexion, while vitamin E can help to strengthen the skin’s moisture barrier.