VITAMIN C IN DERMATOLOGY
Vit. C, the most plentiful antioxidant in human skin, forms a part of the complex group of enzymatic and non-enzymatic antioxidants that co-exist to protect the skin from reactive oxygen species (ROS)... Vit. C protects the skin from oxidative stress by sequentially donating electrons to neutralize the free radicals.
Antioxidants are necessary for neutralizing the ROS formed due to UV exposure. It is important to note that Vit. C is equally effective against both UVB (290-320 nm) and UVA (320-400 nm).[2,5] ... Although Vit. C alone can provide photoprotection, it works best in conjunction with Vitamin E (Vit. E), which potentiates the action of Vit. C four-fold. Hydrophilic Vit. C helps regenerate Vit. E, a liphophilic antioxidant. Thus, Vit. C and Vit. E together protect the hydrophilic and lipophilic compartments of the cell, respectively. Vit. C and Vit. E synergistically limit chronic UV damage by significantly reducing both cell apoptosis and thymine dimer formation.
From a clinical point of view, it is important to note that the efficacy of the Vit. C serum is proportional to the concentration, but only up to 20%. The half-life in the skin after achieving maximum concentration is 4 days. A persistent reservoir of Vit. C is important for adequate photoprotection, and can be achieved by regular 8- hourly applications. As UV light lowers tissue Vit. C levels, topical Vit. C is best used after exposure to UV light and not prior. A combination of tyrosine, zinc and Vit. C has been shown to increase the bioavailability of Vit. C 20-times vis-à-vis using just Vit. C.