However, he adds that it's possible to get the same level of antioxidants in makeup as in treatment products -- look for products that contain several antioxidants rather than just one, which indicates well-considered formulation and, most likely, better effectiveness than a formula that relies on just one antioxidant ingredient.
What is it: One of the main components of the skin, it helps preserve structure and moisture. As we age, the amount in our skin decreases. Injectable fillers such as Restylane and Juvéderm use a man-made equivalent. But in topical skin care, hyaluronic acid is used primarily for its moisturizing properties.
Where to find it: Hyaluronic acid is often paired with peptides. But in Jane Iredale Liquid Minerals ($46) makeup, spheres of titanium- and zinc-based foundation are suspended in a serum that contains hyaluronic acid as well as free radical-fighting vitamin C and Coenzyme Q10.
Will it work: Hyaluronic acid has been in skin care products and cosmetics for a couple of years. Medical journals have published no clinical studies on topical application, Kim says, and "to claim that hyaluronic can rejuvenate the skin by applying it topically is probably a stretch, but it's very good for the skin because it's very moisturizing."
What is it: A plant-derived acid that controls the Ph levels on the surface of the skin, preventing bacteria that can cause acne.
Where to find it: Neutrogena Skinclearing Oil-Free makeup ($11.50) has oil-absorbing powders to help control shine, plus vitamins A, C and E, as well as 0.5% salicylic acid to help prevent break-outs. Almay Clear Complexion Liquid makeup ($12) has 0.6% salicylic acid and a botanical called meadowsweet, which has vitamin C and naturally occurring salicylic acid.
Will it work: Salicylic acid has been around for about a century and can be used as high as 2% in over-the-counter products. UCLA's Kim cautions that it might irritate sensitive skin but adds, "We know salicylic acid helps with acne, and even if it's not in as high quantities as in some skin care products, that doesn't mean it couldn't help someone with occasional break-outs."
PEPTIDES AND MORE
What are they: Some peptides (chains of amino acids) function as messengers in the skin, allowing the epidermis and dermis layers to communicate more efficiently, and some stimulate collagen production; others claim a Botox-like effect by sending a signal through the skin to the muscles to "turn down" the strength of contractions - with the idea that as the muscles contract less, lines will be less noticeable. If your product lists hexapeptides, polypeptides, GABA or SYN-AKE (a synthetic form of snake venom that relaxes muscles), you're in the peptide ballpark.
Where to find them: Revlon's Age Defying Makeup ($14) has a patented blend of hexapeptides and botanicals called Botafirm. Smashbox's newest powder foundation, called Halo Hydrating Perfecting Powder ($66, including brush), has hexapeptides (and goji berry antioxidants), which it claims reduce fine lines and wrinkles by rebuilding the skin.
Will they work: No medical journal studies prove peptide efficacy, Kim says. "The idea is reasonable to deliver small peptides though the skin but I think we still need some time to evaluate and see if these really work."