“I think vitamin C is great for everybody,” Prather says. “Younger people may not need it, so if you’re under 25, you don’t necessarily have sensitive skin and you don’t need the protection,” she says.
When searching for products, Prather explains that it’s helpful to know that vitamin C serums contain one of three main forms of vitamin C.
- L-Ascorbic Acid This is the most frequently used format.
- Sodium Ascorbate A more stable form of vitamin C, this version is often included in serums designed to be used twice daily.
- Tetrahexyldecyl Ascorbic Acid (THD) Often found in creamy Vitamin C-infused products, THD resists oxidation, so your cream or serum will retain its color over time.
When is the best time to use a vitamin C serum? “I like to use it in the morning: I wash my face, use the vitamin C serum, and then apply sunscreen,” says Divya Sachdev, MD, board-certified in dermatology and internal medicine at Coast Dermatology Medical Associates in Torrance, California.
That last part is key: Vitamin C makes your skin more sensitive to sunlight, so you’ll need to use a sunscreen (look for one with a broad-spectrum formula with at least SPF 30) to protect your skin from side effects like sunburn.
If the product instructions say to use it at night, Prather recommends washing your face and applying a vitamin C serum, followed by a cream that contains other active ingredients, like growth factors. The key is to work your way up from the lightest, thinnest product to a thicker cream. Allow each layer to dry on your skin before applying the next, Prather adds.
Please note that Vitamin C has a tendency to change color when exposed to light. These products are typically packaged in dark bottles to minimize light exposure. However, repeated openings allow light and heat into the bottle, so you can expect the color of your C serum to change to a yellow or orange over time. This change in color will not affect the effectiveness of the serum.
Still, be sure to store the product in a cool, dark place, says Dr. Huang, and for vitamin C that contains L-ascorbic acid (the type of vitamin C most at risk of oxidation), Prather advises using it within six months of opening.
