Vitamin C is a component that cannot be made by our body. The human body needs this and other vitamins for our overall health, and to support various tissues like skin and bones. Vitamin C plays an important role in collagen production.
Frequent lack of Vitamin C in your body can create a condition called scurvy.  Fortunately, modern cases of scurvy are extremely rare.

(It was commonly associated with sailors in the 16th to18th centuries who typically navigated long voyages without enough Vitamin C and frequently perished from the condition. The British Royal Navy started carrying limes or lemons with them in the early 19th Century to combat this disease, and their sailors were frequently referred to as “Limeys”).

Alright, back to modern times.  As stated, the lack of Vitamin C can speed the aging process. Because Vitamin C is an important component in collagen production, the lack of it will weaken collagen production, and can often lead to premature aging.
Sagging skin, wrinkles, dark spots, discolorations, dry and flaking skin are often the result of deficiency of Vitamin C in the body.