Topical vitamin C is a science-backed, dermatologist-favorite ingredient that may help slow early skin aging, prevent sun damage, and improve the appearance of wrinkles, dark spots, and acneVitamin C moisturizer can be used daily or every other day. You may want to use it less often (or not at all) if you have extremely sensitive or oily skin.
the best time to apply vitamin C serum is in the morning, after cleansing and toning your complexion, and before moisturizer and SPF. If you want to maximize the perks, and don't have overly sensitive skin, you can apply it in the morning and evening.