Antioxidant Skin Care/Topical Vitamin C Science
Recent research at Duke University demonstrates how topical vitamin C (L-ascorbic acid) benefits skin. First, the Duke studies show how to get large amounts of vitamin C into skin: the vitamin C must be in the form of L-ascorbic acid at low pH. Once in the skin, additional studies show that L-ascorbic acid has the following effects: it stimulates collagen synthesis, provides photoprotection, stays in skin for up to 72 hours, and prevents UV immunosuppression, a reaction which occurs in more than 90% of skin cancer patients. For reasons that aren't entirely clear, sunscreens don't fully protect individuals against UV immunosuppression.

Topical vitamin C (L-ascorbic acid) protects skin against and reduces harmful effects caused by sunlight in both the UVB and UVA bands (290-400 nm). Although topical vitamin C does not absorb light in this range, and hence, is not a sunscreen, vitamin C (L-ascorbic acid) exerts its effects by neutralizing reactive oxygen species, the highly-reactive molecules produced when sunlight interacts with cell membranes and other components of skin tissue. And, unlike sunscreens, once vitamin C gets into skin, it cant be washed, rubbed, or perspired off. Research shows that topical vitamin C (L-ascorbic acid) is an excellent antioxidant for skin protection and should be a useful adjunct to (but not replacement for) sunscreens. Recent scientific findings also reveal that it is the long UVAI (340-400 nm) rays that cause photoaging, and no currently available sunscreen fully protects individuals from all long UVA radiation.

L-ascorbic acid is the only form of vitamin C that can be used by the body.