6 Vitamin C Mistakes You’re Probably Making

Using too many skin-care products with vitamin C

Too much of a good thing could actually do more harm than good. Consumers often don't realize that L-ascorbic acid, ascorbyl phosphate and tetrahexyldecyl ascorbate are all forms of vitamin C, says New York dermatologist Elaine Kung, MD. “Oftentimes, a low concentration of vitamin C may be in any or all of our skin-care products—including cleansers, serums, moisturizers and even sunscreens.”

Buying incorrectly packaged vitamin C products

“Clear medicine dropper bottles allow ultraviolet light and air into the container, which may alter or degrade the vitamin C serum. Oxidation of vitamin C serum may change the potency or pH of the product,” says Dr. Kung. She recommends consumers buy vitamin C products housed in airless pump bottles. As an added benefit, she thinks “airless pump bottles may prevent overusing skin-care products because they allow for metered dosing. Meaning, one pump is enough to cover the face.” If you do buy a vitamin C in a glass dropper bottle be sure it's dark enough to protect from oxidation.

Pairing vitamin C with other harsh ingredients

Vitamin C on its own can be irritating, so we have to be mindful when using it alongside other ingredients that can increase skin irritation. Dr. Kung explains that combining AHAs, BHAs, retinol or benzoyl peroxide with leave-on vitamin C products on the same day can lead to dryness and irritation.

Purchasing discolored products

As explained, vitamin C can oxidize, sometimes before you even buy it. “The discoloration indicates that the products are old or have been exposed to extreme conditions (heat/sunlight), which oxidizes the vitamin C, thereby rendering them less effective,” says Washington D.C. dermatologist Tina Alster, MD. If you spot vitamin C products in stores that appear amber or brown, don’t waste your time with them.

Overdoing it with potent vitamin C serum

When a formula is especially potent, you don’t need to use quite as much. “Sometimes, people squeeze a coin-size amount of 10 to 20 percent vitamin C serums which can be quite irritating, especially if the formulation has an acidic pH,” says Dr. Kung. Be sure to know how potent your product is before overdoing application.

Applying vitamin C at night

While it’s not necessarily wrong to use vitamin C at night, Dr. Alster recommends it be applied in the morning, under mineral SPF, of course. Applying it in the morning makes it even more beneficial. “Its antioxidant activity provides additional photoprotection,” she says.