We get a lot of questions about vitamin C. Vitamin C is a topical antioxidant that we frequently recommend. We use it to prevent and reverse oxidative stress, which shows up in your skin as pigmentation, dullness, and loss of elasticity (wrinkles). It is not the only topical antioxidant, but it is probably the most studied. It is important to know that not all forms of topical vitamin C are created equal. There are four common forms of Vitamin C in topical formulations: ascorbic acid, sodium ascorbyl phosphate, ascorbyl methylsilanol pectinate, and tetrahexyldecyl ascorbate.
Ascorbic acid is the bioavailable or active form of vitamin C and is the most common vitamin C in topical formulations. It is an acid, so it is only water soluble, and the formulation can be irritating to some. In order to be effective, concentrations should be between 8-20%, so there is no benefit to going above 20%. While effective, this form of vitamin C is extremely unstable and reacts with everything from light, heat, oxygen, water, and metals. This makes the shelf life very short, causing an increase in the cost. In order to be effective, the companies who manufacture this type of vitamin C have to account for these challenges. Lastly, we typically avoid this formulation in those with sensitive skin and acne prone skin.
The next two forms are not in a lot of products you will find in our office: sodium ascorbyl phosphate and ascorbyl methylsilanol pectinate. Both of these are inactive forms, meaning it requires transformation into the active form once it is absorbed into your skin. Both of these are still relatively unstable.
The last form of vitamin C on the list is tetrahexyldecyl ascorbate. This is the only formulation that is oil soluble, meaning that it is not converted into the active form until it comes into contact with the oils in your skin. It also results in a slower release of the active ingredient and does not cause as much irritation because it does not have to be at a low pH (acidic pH). Slower release also results in longer active time in your skin. Some studies show that this form improves collagen synthesis more than ascorbic acid.
The takeaway point here is to remember how to read labels. Know what's in your products and why you are using them. We hope you have a better understanding of what vitamin C is in skin and why it can be pricey to boot!
