VITAMIN C IS THE MOST ABUNDANT ANTIOXIDANT IN human skin. Despite high doses of oral supplementation, only a small fraction of vitamin C will be biologically available and active in the skin. Therefore, we rely entirely on external supplementation, such as topical application in the case of cosmeceuticals.  Vitamin C is essential for collagen biosynthesis and more importantly, it serves as a cofactor for prolyl and lysyl hydroxylase, key enzymes that cross-link and stabilize collagen fibers.

Vitamin C also directly activates the transcription factors involved in collagen synthesis and stabilizes procollagen messenger RNA (mRNA) that regulates Type I and III collagen synthesis. In addition, vitamin C increases the gene expression of collagen and synthesis of the tissue inhibitor of MMP-1, which decreases collagen degradation. A clinical study showed that daily application of three-percent topical vitamin C over a four-month period led to a significant increase in the density of dermal papillae

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