Further Information Ascorbic acid, vitamin C, is derived from glucose and many animals can make it starting from glucose. Primates like humans can’t synthesize it (we lack an enzyme in that pathway), making ascorbic acid a vitamin because we cannot make it but need it, so we have to ingest it from a source that is contains it, like orange and amla fruits (or from SAS!).

The vitamin C we ingest with our food and multivitamins may not reach our skin in quantities high enough to do everything that vitamin C is supposed to do. Ascorbic acid (and derivatives that our body can use) protect us from free radicals like those formed during exposure of our skin to UVA and UVB radiation. Ascorbic acid is also necessary to synthesize collagen, where is required to hydroxylate the amino acid proline after synthesis of the protein. Scurvy is a syndrome of vitamin C deficiency and is related to defective collagen synthesis.

Ascorbic acid is known to inhibit synthesis of melanin, probably because melanin is made by our skin in response to stress, and ascorbic acid is in the first line of defense, preventing the damage before melanin synthesis can be initiated. Ascorbic acid and its derivatives promotes wound healing, controls inflammation and reduces erythema.

In short, ascorbic acid is a safe active that will bring multiple benefits to your skin, preventing future damage but also repairing past damage to your skin by age and sun.

References

Lanigan, Rebecca S. (1999) Final report on the safety assessment of ascorbyl palmitate, ascorbyl dipalmitate, ascorbyl stearate, erythorbic acid, and sodium erythorbate.     International Journal of Toxicology: 18(Suppl. 3), 1-26. 

Ashino H, Shimamura M, Nakajima H, Dombou M, Kawanaka S, Oikawa T, Iwaguchi T, Kawashima S. (2003) Novel function of ascorbic acid as an angiostatic factor. Angiogenesis: 6(4):259-69.   

http://en.wikipedia.org/wiki/Ascorbic_acid