If you’ve spent time exploring the skin-care side of TikTok, you know that dermatologists love to tout the benefits of vitamin C serums and creams. They claim the vitamin can brighten and firm the skin, protect it from sun and environmental damage, diminish dark spots, and even reduce the signs of aging.
“All of its various benefits make it a top recommendation for most dermatologists,” said Dr. Fatima Fahs, a dermatologist in Michigan.
Yet, if you dig into the research on how vitamin C actually affects the skin, a different picture emerges. In a 2021 review published in The Journal of Cosmetic Dermatology, for instance, Fahs and her colleagues evaluated how effective various vitamin C formulations were at improving skin health. They concluded that although some formulations seemed to benefit the skin, the overall results were mixed.
The problem is that although vitamin C is probably good for the skin, it’s hard to make a product that works the way it’s supposed to.
How Vitamin C Works — in Theory
Research suggests that when vitamin C penetrates the skin, it protects and improves it in various ways.
It’s an antioxidant, so it can neutralize damaging molecules called free radicals, which “accelerate signs of aging,” said Dr. Whitney Bowe, a dermatologist in New York City.
Vitamin C can also stimulate the skin’s production of collagen, a protein that increases skin firmness and elasticity and helps keep it plump and hydrated. Because of this, “using a powerful, stable vitamin C serum consistently over time can help smooth out the appearance of fine lines and wrinkles,” Bowe said.
Finally, vitamin C can brighten dark spots because it inhibits an enzyme called tyrosinase that causes skin discoloration, Bowe said. Although there has been little research on how effectively vitamin C does this, a small study published in 1996 found that vitamin C reduced the appearance of dark skin patches or age-related freckles in 19 out of 34 people who used it.
Why Some Products Don’t Work
Some vitamin C products aren’t made in ways that ensure that the vitamin actually gets into the skin and does its job. “You really have to understand how to formulate them and how to package them properly,” and not all companies get that right, said Dr. Patricia Farris, a dermatologist in Metairie, Louisiana.
Vitamin C is an unstable molecule and can easily break down into a different molecule that doesn’t help the skin, Bowe said. For example, L-ascorbic acid, a form of vitamin C found in many skin-care products, degrades when it is exposed to heat, a high pH or sunlight, she said — which can happen during transit and storage.
Even if the vitamin C in a product remains stable, it may not penetrate the skin deeply enough to benefit it. The skin’s outermost layer repels water-loving molecules such as L-ascorbic acid — and that means that the molecule may not get sufficiently absorbed, Bowe said.
Other derivatives of vitamin C, such as tetrahexyldecyl ascorbate and tetra-isopalmitoyl ascorbic acid, have a different chemistry and can more easily penetrate the skin’s outer layer, which is why some products contain those forms of the vitamin instead, Bowe said. Those formulations can also be gentler on the skin.
But these forms of vitamin C are relatively new and do not have as much research supporting their benefits, Fahs said. “The reality is: Human studies showing efficacy are still very limited,” she said.
Picking a Product
If you are considering a vitamin C product that contains L-ascorbic acid, Fahs recommended looking for a formulation that also contains vitamin E and ferulic acid, both of which can improve the vitamin’s stability and how well it penetrates the skin.
To maximize the chance that a vitamin C product will work, opt for one that is housed in opaque packaging and uses a pump applicator rather than a dropper, Bowe said. These features help prevent the vitamin C from degrading.
Farris recommended using vitamin C products made by trusted larger skin-care companies, such as SkinCeuticals, which are more likely to perform clinical testing for efficacy than smaller cosmetics companies.
Because L-ascorbic acid can cause irritation, people with sensitive skin or rosacea may want to use a product that contains one of the gentler forms of vitamin C, such as tetrahexyldecyl ascorbate, Fahs said.
Still confused about what, if anything, to buy? Talk to a dermatologist, Bowe said, although some doctors may be more knowledgeable about the research than others.
“Don’t be afraid to ask questions to optimize your skin care,” she said. “You deserve to find the products that work best for your skin’s needs.”—NYT