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How to Choose and Use Vitamin C Serum

By Dr. Joyce Park M.D.

Vitamin C has become a buzzword in skincare lately, being touted as a super ingredient that helps your skin to turn back the hands of time. But what does this ingredient really do, and how well does it work?

Antioxidant Power of Vitamin C Serum

Vitamin C comes in various active forms, and L-ascorbic acid is the most heavily researched and commonly used one. It works by acting as a mega antioxidant, scavenging harmful products in the skin. Let’s break down what that means. Various environmental stressors like pollution, smoking, and sunlight can generate reactive oxidative species in the skin. Think of these as toxins that can cause damage to the proteins and membranes in your skin cells, leading to a breakdown of collagen. This process, in turn, shows up on your skin as wrinkles, dark spots, red spots, and decreased skin quality and texture. Vitamin C combats all of this damage, and using a daily Vitamin C serum helps to prevent these changes from occurring in your skin. In fact, studies have shown that people who use ascorbic acid have a significant decrease in wrinkles compared to those who don’t! (Keep in mind that this study was performed with freshly prepared Vitamin C products, which is different from that vial of Vitamin C that has been sitting on your shelf for months. More on that below!)

Added Benefits of Vitamin C Serum

Aside from its antioxidant powers, Vitamin C also helps protect and treat the skin in a number of other ways. It plays a vital role in collagen production, which is a key process that slows down with age. Vitamin C also decreases production of melanin, or pigment, which helps to treat conditions such as age spots or melasma. Together with its friend Vitamin E, Vitamin C also helps to boost the ability of the skin to resist ultraviolet radiation-induced damage. Vitamin C substantially improves and accelerates the wound-healing process as well.

Choosing Your Vitamin C Serum

Given the complicated chemistry behind this ingredient, how do you choose the right product for you? L-ascorbic acid works best at a low pH, meaning at an acidic level. The best concentration of vitamin C in a product to maximize benefits is around 8% or higher, and anything above 20% is not that much more helpful. In fact, it may cause some irritation!

How to Use Vitamin C Serum

The biggest difficulty with Vitamin C in a topical form is stabilizing the active ingredient. Vitamin C is a very finicky ingredient, and is prone to breaking down, starting from the moment that it is dissolved in water. In order to get the most out of your Vitamin C product, I recommend keeping the preparation in a cold dark place. Opaque packaging that doesn’t let light through helps to keep the molecule stabilized. You don’t want to keep the product in your bathroom because it is being heated with each shower, and you definitely don’t want a product that is kept in a jar, since it is fully exposed to air every time you open it. I personally keep mine in the refrigerator! Sure it means taking a few extra steps each morning from the bathroom, but storing my Vitamin C there helps to prolong the shelf life of my product. In terms of when to use this ingredient, Vitamin C should be used after you cleanse and tone your face, and before you use moisturizer and finish off with sunscreen.

Now that I’ve gone over the skinny on this antioxidant, I hope that you understand better how Vitamin C can benefit the skin!

This article was written by Dr. Joyce Park, a senior dermatology resident in NYC and skincare and beauty blogger at She is originally from Northern California, and she earned her B.A. and MD at Stanford University. Dr. Park has a background in medical journalism, having worked at both the medical units of NBC News and ABC News, and she is interested in using social media to educate the public about skin health.


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