Vitamin C (Ascorbic Acid)
Definition
Vitamin C (L-ascorbic acid) is one of the most researched and effective antioxidant ingredients in skincare. It neutralizes free radicals caused by UV exposure and pollution, brightens the skin by inhibiting the enzyme tyrosinase (which produces melanin), stimulates collagen synthesis, improves skin texture, and enhances sun protection when used under sunscreen. L-ascorbic acid is the most potent and bioavailable form, most effective at concentrations of 10-20% and at a pH below 3.5. However, it is notoriously unstable — it oxidizes quickly when exposed to air, light, and heat, turning yellow-brown and losing effectiveness. More stable derivatives like sodium ascorbyl phosphate, ascorbyl glucoside, and ascorbyl tetraisopalmitate are available but may be less potent. Vitamin C serums are typically applied in the morning before sunscreen. Some people experience initial tingling, which usually subsides as the skin adjusts.
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