Vitamin C is well known for boosting collagen productionTrusted Source.

Collagen is a naturally occurring protein that depletes over time. Lower levels of collagen can lead to fine lines and wrinkles. Collagen production is tied to skin elasticity and firmness. When your collagen levels begin to drop, your skin may begin to sag.

Applying a vitamin C serum will boost collagen production, resulting in an overall tighteningTrusted Source effect.