Vitamin C (in the form of ascorbic acid) is one of the few skincare ingredients that lives up the the hype. The American Academy of Dermatology recommends the use of vitamin C to treat signs of prematurely aging skin, such as fine lines and hyperpigmentation (age spots). The Cleveland Clinic also recommends it for rosacea and melasma, especially for people with sensitive skin or darker skin (African American, Native American, Asian, Hispanic, or Southern European).
So it's not surprising that there are so many vitamin C skincare products on the market. Unfortunately most of them are expensive or ineffective (or both!). Here's an alternative. It has the same ingredients as the most effective products, but is about one-tenth the price.
This is the vitamin C serum you should be using.
American Academy of Dermatology: Aging skin and skin care productions
Cleveland Clinic: Skin conditions