Vitamin C Type of ingredient: Antioxidant Main benefits: Protects against free radical damage, evens skin tone, and promotes collagen production. Who should use it: Vitamin C is not recommended for those with extremely sensitive skin and can be problematic for those with oily skin. Herrmann recommends asking your board-certified dermatologist which brand may be best suited for your skin type. How often can you use it: Herrmann recommends using vitamin C daily or every other day. Works well with: Vitamin C works well with complementing antioxidants like, vitamin E and ferulic acid, which will boost the efficacy and stability of the molecule.
Don't use with: According to Herrmann, avoid it using with benzoyl peroxide, which can oxidize the vitamin C and make it useless very quickly. Also avoid using it with other acids, which may cause excessive skin irritation, especially if used daily. And lastly, don't it use with retinol, which can make the vitamin C more unstable and less likely to penetrate the skin.
What is Vitamin C?
According to Robinson, vitamin C is an essential nutrient required for the growth and repair of tissues in all parts of the body, including the skin, but we cannot produce it on our own. The powerful antioxidant is found naturally in fruits and vegetables and commonly produced synthetically in skincare products, such as moisturizers, toners, and, most often, serums.
The first form of vitamin C worth mentioning is the pure form, L-ascorbic acid. Herrmann says this is the most biologically active and well-studied form of vitamin C, but there are also several vitamin C derivatives, such as sodium ascorbyl phosphate, ascorbyl palmitate, retinyl ascorbate, tetrahexyldecyl ascorbate, and magnesium ascorbyl phosphate. "These derivatives are not pure vitamin C, rather they are combined with other ingredients, which might help to keep the vitamin C stable," Robinson explains. "So when these derivatives come in contact with the skin, they release the pure vitamin C onto the skin." For example, he says if a product contains 10 percent of one of these derivatives, they might only release 3 percent of pure vitamin C on the skin. Herrmann adds that the variants mostly differ in their hydrophilicity (their ability to easily dissolve in water) and pH.
To understand how vitamin C works, we first need to know how free radicals damage the skin. There are three types of free radicals, but Rouleau is mainly concerned with the reactive oxygen species (ROS). "We are exposed to ROS from the air we breathe (oxygen), cigarette smoke, UV sunlight, stress, and smog," she says. The effects of ROS are no joke: They damage the dermis of the skin and alter DNA, the moisture barrier, skin texture, color, and cell functioning.
To demonstrate the effects of ROS and oxidative stress to the naked eye—and to prove how vitamin C works to combat them—Rouleau devised a simple experiment involving an apple. She coated one end of a slice with a thin layer of vitamin C serum and left the other side completely untouched. Then, she waited for three hours. Here's what happened:
As you can see, the side of the apple that was coated with the vitamin C serum didn't oxidize at all. "This shows how topical vitamin C can prevent oxidation, and therefore, slow down the visible appearance of aging," Rouleau says.
Vitamin C is very reactive and easily loses its antioxidant properties when exposed to heat, light, air, and other chemicals. To prevent it from oxidizing and deactivating, use vitamin C products that come in air-tight, opaque packages and store them in a cool, dark environment. If your product has turned brown, Herrmann says it’s best to toss it and replace it with a new bottle, as this change in color indicates that the formula has oxidized and is no longer effective.
Benefits of Vitamin C for Skin
Vitamin C is an impressive skincare ingredient that is shown to be effective in the following areas:
- Protects against environmental stressors: As an antioxidant, one of vitamin C’s main functions is protecting the skin. "Normal cellular processes, as well as environmental insults like ultraviolet light and pollution, create free radicals in the skin," Herrmann explains. "Free radicals are inherently unstable molecules that damage cells, promoting skin dullness, wrinkles, and even cancers." By scavenging these free radicals, vitamin C protects the skin, keeping it healthy and improving visible signs of aging.
- Promotes collagen production: Vitamin C also plays an important role in collagen synthesis. "Collagen gives our skin support and structure, and as it degrades with age, we begin to notice wrinkles and lines," Herrmann explains. "Vitamin C is a necessary cofactor for building collagen bundles, without which this process halts."
- Lightens brown spots: Vitamin C is also helpful in lightening unwanted brown spots or decreasing brown discoloration by blocking the pathway of pigment synthesis, according to Herrmann.
Side Effects of Vitamin C
Generally, vitamin C is safe for daily use. However, in high concentrations, it can be irritating, especially if mixed with other acids. Herrmann says those with extremely sensitive skin may not be able to tolerate it, and in which case, should avoid it. Many vitamin C products are also oily, which can be problematic for those with oily skin, so Herrmann recommends consulting your board-certified dermatologist to find a brand or product that is best suited for your skin type.
How to Use It
One highly debated topic when it comes to vitamin C is what time of the day is best for application. While some argue that morning is best for protecting the skin, others are in favor of night time when the skin's vitamin C is most depleted. According to Herrmann, consistency is most important, whether you decide to apply it in the morning or before bed, but avoid using it at the same time as benzoyl peroxide. She also suggests using it daily or every other day, and if you're using a serum (the most common vehicle for vitamin C), apply it after cleansing.
As great as it is, vitamin C isn't without obstacles. First of all, it's inherently unstable and reactive and easily loses its antioxidant properties when exposed to heat, light, and air. As a fix, cosmetic companies have been jumping on the powder form of vitamin C to help improve stability, which would, in theory, make it last longer and increase the shelf life.
Unfortunately, though, Herrmann says it’s not as simple as just mixing one part C-powder to one part your favorite moisturizer; Vitamin C also does not easily penetrate the skin's barrier. To be effective, Herrmann says vitamin C must be in a concentration of at least 10%, and the pH of whatever you’re adding it to must be acidic to allow for its absorption. "It’s hard to know the pH of products, and even if you get it right, the powder can crystallize on the skin before it has a chance to absorb, which is a must-do for efficacy." For this reason, Herrmann advises against the DIY trend. "I think it’s wiser to stick with high-quality products that have resulted from extensive research and development to make sure their vitamin C is made available in an optimal formulation for enhanced stability and skin penetration," Herrmann says.
Although it can also be consumed orally, Robinson says because of the level of vitamin C necessary for significant skin improvement, it would need to be applied topically. Ingesting it would likely not provide enough.
The Best Products With Vitamin C
Herrmann (and most other dermatologists) agree that vitamin C's performance is optimized when it's working alongside other powerful antioxidants, and this oil-serum hybrid is loaded with them. Just be sure to shake it up before use; separation is natural and this formula is 88 percent derived from pure, natural, Arctic ingredients. According to Herrmann, vitamin C works best in conjunction with complementing antioxidants, and this serum, one of her top product recommendations, is packed with a whopping 19 of them for increased free radical protection.
A favorite product from Robinson's skincare line, this formula uses 20% L- ascorbic acid combined with EGCG (the most active component in green tea) for ultimate protection. Robinson says this product also has three patents on the ability to encapsulate pure vitamin C so that it does not degrade or oxidize. Bonus: Unlike most vitamin C serums that have a sticky, oily texture, this serum is silky and fast-absorbing.
"Companies often reduce vitamin C serum pH and add complementing antioxidants like vitamin E and ferulic, which help increase the efficacy, making such products superior," Herrmann explains. For that reason, this vitamin C and E and ferulic acid serum is one of her favorites (it's one of ours, too). The way vitamin C is packaged is very important for protecting it from being oxidized, which is why you might be surprised to hear that this tub of cream is one of Herrmann's favorites. But this formula uses tetrahexydecyl ascorbate, a stable form of vitamin C that is also fat-soluble, which allows for better penetration. Another product that contains the stable, lipid-based form of vitamin C, tetrahexyldecyl ascorbate, as well as two other forms of vitamin C (magnesium ascorbyl phosphate and methylsilanol ascorbate) this serum is one of our favorites for creating an even skin tone. Packed with skin-loving ingredients, including five forms of vitamin C, antioxidants (vitamin E, cucumber extract), a blend of peptides, and ubiquinone (aka coenzyme Q10), it's easy to see why this firming and brightening eye cream is one of our all-time favorites.