Vitamin C serum can help your face by protecting it from skin cancer and fighting premature aging. Vitamin C can also promote healing from a cut or a burn. Vitamin C comes in many different concentrations.
This is the most natural form of Vitamin C and a good choice for people who do not have sensitive skin. However if you do have sensitive skin, L-asorbic acid can irritate it. Also, if it is exposed to the air or not stored properly, it can do more harm to your face than good.
Magnesium Ascorbyl Phosphate
This type of Vitamin C serum works well for people with sensitive skin. It is a lower concentration and water soluble so it is easy to put in skin care products. Magnesium ascorbyl phosphate does lose its effectiveness over time and needs to be stored away from direct sunlight.
Ascorbyl Methyl Silanol
This form of vitamin C stores well but apparently it cannot be absorbed by the skin. It will not convert into the natural form of vitamin C that gives your skin benefits.
This product is what is most commonly used in face creams. However this is such a low concentration of vitamin C, it will not give you any of the benefits of vitamin C.
Ascorbic Acid Polypeptides
This type of Vitamin C stores well and provides both skin cancer protection and anti-aging benefits. It is also water soluble.