Welcome to Ask a Derm, SELF’s series where board-certified dermatologists answer your burning questions about skin, hair, and nail health. This time, we spoke with Shasa Foo, MD, director of cosmetic medicine at the University of Miami’s Dr. Philip Frost Department of Dermatology and Cutaneous Surgery. Her areas of expertise include skin cancer detection and treatment, aging and ethnic skin concerns, and skin rejuvenation.
Timing is important for some skin care ingredients — tretinoin, for example, is most effective at night, as it degrades with exposure to light — and you should always apply your sunscreen at least 15 minutes before you go outside to ensure it’s fully absorbed (and your full protection).
Another timing tip we heard from dermatologists is to slather on a vitamin C serum in the morning. As a topical antioxidant, it helps protect skin from environmental aggressors like UV rays and pollution. So when we started seeing a lot of people on SkinTok breaking this golden rule and using vitamin C in their nighttime skincare routines, we were a bit critical at first.Alas, they are wrong. But we wondered: Is there any benefit to using this powerful antioxidant at night? We reached out to Shasa Hu, MD, board-certified dermatologist and associate professor at the University of Miami Miller School of Medicine, for her opinion.
In the end, it is completely That’s a no-brainer. Applying vitamin C at night can have some benefits, Dr. Hu tells SELF, including reducing pigmentation and increasing collagen production, the protein that keeps skin firm and minimizes wrinkles. But using vitamin C at night is also a bad idea.
Going back to the antioxidant benefits mentioned above, a properly formulated vitamin C serum essentially neutralizes free radicals – volatile molecules the body produces in response to environmental hazards like air pollution (including cigarette smoke) and the sun’s UV rays – that can damage skin and inhibit its ability to repair itself. As a result, using a vitamin C serum in the morning can help prevent sunburn (especially if it also contains vitamin E, another great antioxidant) and reduce DNA damage caused by UV exposure, says Dr. Hu. While it’s by no means a replacement for SPF, “applying vitamin C under your sunscreen is like adding a booster, giving your skin extra protection from UV damage all day,” he adds.
Daytime-specific benefits aside, there are a few reasons why you might not want to take vitamin C before bed. First, if you’re using other powerful active ingredients in your nighttime routine, adding another powerful antioxidant to the mix could be irritating, says Dr. Hu. For example, applying vitamin C at the same time as an AHA like retinol or glycolic acid could be too harsh and cause reactions like redness, stinging, dryness, and peeling, especially if you have sensitive skin.
Additionally, taking vitamin C in the morning, regardless of other ingredients, and Using double that amount at night could similarly damage your skin’s barrier and irritate your face, she adds. (On the other hand, if you want to take the gentler route, Dr. Hu says that tetrahexyldecyl ascorbic acid is a gentler type of vitamin C compared to L-ascorbic acid, which is the purest but most potent form.)
To sum up Dr. Hu’s advice, there’s nothing wrong with applying Vitamin C at night, but it makes a lot more sense in the morning. And since we subscribe to the WWDD (What Would a Dermatologist Do?) philosophy, we’ll follow her advice: “I personally only use Vitamin C in the morning because I believe skincare is more of a marathon than a sprint. Slow and steady over time will give you the best results in the long run!”
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