Ascorbic acid—also known as L-ascorbic acid—has the most research of any form of vitamin C when it comes to benefits for skin. It is a potent antioxidant and skin-soothing agent that can improve the appearance of signs of aging.
Ascorbic acid is also a powerhouse when mixed with other antioxidants, or when used alone in higher concentrations, such as 15% or 20% or greater, amounts that can be great for evening out skin tone.
A particularly vulnerable antioxidant when exposed to UV light and air, ascorbic acid must be packaged to protect it from these elements during routine use, or its effectiveness will gradually become diminished to the point of not working at all (you will see this as oxidized discoloration, meaning the product turns a copper to brownish color). For this reason, avoid any vitamin C (ascorbic acid) products packaged in jars.
What about using vitamin C (ascorbic acid) and niacinamide in the same product or applied at the same time in separate products?
You might have read or heard that niacinamide and vitamin C shouldn’t be used at the same time, whether found together in the same product or applied separately one after the other. Rest assured, this combination is fine and is in fact quite beneficial!
The research this misconception is based on was conducted in the 1960s; the forms of niacinamide and vitamin C used in this study were not stabilized—although niacinamide itself is very stable. The base of the formula used in this study was also far different than today’s sophisticated skincare formulas. Today, cosmetic chemists know how to combine niacinamide and vitamin C in the ideal base formulas that enhance their compatibility.
The other common concern we’ve seen about combining these two ingredients has to do with the pH range. The concern is that the acidic environment ascorbic acid needs to be most effective will cause niacinamide will convert to nicotinic acid, a form that can be sensitizing, possibly inducing redness. Good news: This conversion process would only happen under conditions of the formula being exposed to very high heat for a long period of time. This would not apply to layering skincare products or to heat conditions that occur during manufacturing, transport, and storage of cosmetic products that contain niacinamide and ascorbic acid.
What all of this means is that you can use or layer products containing both niacinamide and vitamin C knowing that they will not render each other any less effective. Each of these ingredients on its own can help to address dark spots, uneven skin tone, wrinkles, loss of firmness, and dullness. When used together, they become even more of a powerhouse! This duo will help give you an even better chance at achieving a radiant, smooth, even, younger-looking complexion.
References for this information:
Journal of Drugs in Dermatology, January 2012, issue 1, pages 51-56
AAPS PharmSciTech, September 2011, issue 3, pages 917-923
Journal of the American Academy of Dermatology, September 2008, issue 3, pages 418-425
Dermatologic Surgery, July 2005, issue 7, part 2, pages 814-817
Dermatologic Surgery, February 2001, issue 2, pages 137-142