Yes — but with real caveats about formulation. Topical vitamin C (L-ascorbic acid and its derivatives) has genuine evidence for antioxidant photoprotection, modest collagen support, and brightening of hyperpigmentation.
The mechanism is dual. Vitamin C is a required cofactor for the enzymes that hydroxylate proline and lysine in collagen synthesis — so adequate skin vitamin C literally enables collagen production. Independently, it's a potent antioxidant that neutralizes UV-generated reactive oxygen species before they damage lipids, proteins, and DNA (Pullar, 2017).
Clinical evidence: Traikovich's 1999 controlled trial showed measurable improvement in fine wrinkles, roughness, and dyschromia after topical vitamin C use (Traikovich, 1999). Additional studies have shown it enhances the photoprotective effect of sunscreen when applied underneath (Farris, 2005).
Formulation matters enormously. L-ascorbic acid is only stable at pH under 3.5 and degrades rapidly with light and air exposure. A vitamin C serum that isn't in an opaque bottle, isn't formulated at the right pH, or has turned yellow-brown is doing very little.
Look for: L-ascorbic acid at 10-20%, pH 2.5-3.5, opaque or amber packaging, often stabilized with ferulic acid and vitamin E. Or a derivative like tetrahexyldecyl ascorbate (more stable but less studied). Serums that check out are worth using; most drugstore versions are not.