Since collagen fibers in the dermis give your skin that taut, youthful appearance, they can only improve a daily body moisturizer, right? Not quite. Moisturizer manufacturers may advertise collagen-enriched formulas, but dermatological research hasn't found any evidence that the protein improves skin condition [source: Carlson, Eisenstat and Ziporyn]. In fact, collagen molecules are simply too large to penetrate the epidermis to work their supposed magic [source: Goldberg and Harriot]. Yeast extracts, which are thought to smooth wrinkles, and liposomes and cerebrosides, meant to mimic the skin's production of moisture-binding essential fats, are similarly ineffective.