L-ascorbic acid at pH below 3.5 and concentrations of 10-20% provides photoprotection and collagen synthesis, but formulation instability remains the primary challenge

This clinical review examined the evidence for topical vitamin C (ascorbic acid) in dermatological practice. The most effective form, L-ascorbic acid, requires formulation at pH below 3.5 and concentrations of 10-20% for optimal skin penetration. Clinical studies demonstrated benefits including increased collagen synthesis, photoprotection against UVA/UVB damage, and reduction of hyperpigmentation. The primary limitation is L-ascorbic acid's instability — it oxidizes rapidly when exposed to air and light. Newer derivatives (ascorbyl palmitate, magnesium ascorbyl phosphate, ascorbyl glucoside) offer improved stability but reduced potency. The review guides consumers in evaluating vitamin C serum formulations.

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