Beauty sleep is real. Researchers confirmed it in a study published earlier this year: People who had dark-circles and puffy eyes, telltale signs of lack of sleep, were rated as appearing less healthy and approachable. I find this both alarming and vindicating. It’s alarming because of my consistent lack of sleep; it’s vindicating because I’ve often relied on oils, serums and the rest of my extensive nighttime beauty routine to compensate for it.
However, dermatologist Fayne Frey says we put too much stock into sleep’s effect on the skin. “I have never seen a double-blinded control study that correlates stages of sleep with skin activity,” she tells me over the phone. “Although there may be physiological differences in the skin when an individual is lying down and inactive, when fluid shifts away from dependent areas like the legs due to gravity, an evening skin repair system has never been elucidated.”
So what actually happens to our skin at night, and do we really need separate beauty products for sleep? How much should we buy into marketing that sells us overnight skin repair? I talked to Dr. Frey and two other dermatologists to find out.
Cell turnover happens constantly
According to the American Academy of Dermatology, humans shed their entire outer layer of skin about every four weeks through a process known as cell turnover.
“The concept of cell turnover generally refers to the continual shedding of dead skin cells and their replacement with new cells,” says Dr. Sejal Shah, a New York-based dermatologist and RealSelf contributor. “The skin produces new skin cells that travel from the lowest layer of the epidermis to the top layer and then shed off the skin surface.”
Dr. Neal Schultz, board-certified dermatologist and founder of DermTV.com, explains that since the epidermis, the upper layer of the skin, serves as barrier against pollution and germs, “the process of cell turnover is partly responsible for the healing of your cuts.”
The process isn’t much different at night, but it does happen at a higher rate
“Like other physiological processes in your body, those of the skin cycle are in a circadian rhythm [a 24-hour cycle],” Dr. Shah says. “Basically this means that different processes take place or occur maximally at the different times during the day. Cell turnover and proliferation and DNA repair are highest at night.” She also says skin’s permeability is higher at night.
Adds Schultz: Products can absorb and work more efficiently at night, given that your skin is free of makeup and sunscreen and environmental factors.
This doesn’t mean, however, that the process of skin repair stops during the day. “Skin may get a ‘rest’ from the daily exposures of ultraviolet light from the sun, or cigarette smoke perhaps, but skin repair does not cease when the alarm clock rings at 7 a.m.”
(Lack of) sleep does not impact cell turnover, but it does show up in other ways
Dr. Frey says that general health, including a good night’s sleep, is likely good for the skin. “There is a plethora of literature on the health benefits of getting adequate sleep. When my patients ask me the best recipe for healthy skin, one of the answers is sleep,” she says. Dr.Shah concurs: She recommends her patients get seven to nine hours of sleep a night.
Lack of sleep can cause or increase dark circles under the eyes, and it can also temporarily increase the appear of lines and wrinkles, Dr. Schultz says. “When the body is tired, production of the chemical cortisol is increased to help give you the energy you need to stay awake and to fight the stress of fatigue. Among many other things, cortisol increases the volume of blood in the blood vessels, including the ones below your eyes which encourages them, increasing the appearance of dark circles which are mostly caused by seeing blood vessels through the skin.”
It’s important to note, though, that these symptoms of lack of sleep have nothing to do with skin function or cell turnover.
Forgot to remove your makeup at night? It’s not as bad as you think
“Most women think terrible things will happen to their skin by not taking off their makeup before bed, and the reality is, it’s usually not much of a problem – so long as it’s not a daily habit,” Dr. Schultz says. There’s not much difference between wearing makeup the eight hours you’re sleeping versus the 12 hours you wear it during the day.
“Unless an individual is allergic or sensitive to one of the ingredients, there is no quality science that proves wearing makeup to bed harms the skin in any way,” Dr. Frey says. “Even ‘acne cosmetic’ (acne caused from makeup) is controversial and studies are mixed.”
Some dermatologists say that sleeping in your makeup clogs your pores, although that could just be a side effect of wearing makeup in general. Either way, proceed with caution.
The products that can boost nighttime skin repair
Dr. Frey says moisturizer is the best nighttime skincare product, plain and simple. “Cell turnover is optimized by maximizing stratum corneum [outermost layer of the epidermis] hydration.” When we’re dehydrated, skin cells ‘hang on,’ and the skin appears flaky,” she says.
Dr. Shah agrees: “I also recommend a good moisturizer because there is some increased moisture loss at night.”
Exfoliants, such as AHAs, BHAs and retinoids, also make a difference, as they get rid of dead skin cells. It’s generally best to use these at night because they increase sensitivity to the sun. Peptides and antioxidants are also good for the skin, and Dr. Schultz says these are also best used at night.
But skip the “night cream”
As with most beauty and wellness topics, beauty sleep and the concept of nighttime skin repair is one that Dr. Schultz and Dr. Frey advise consumers to be critical of when it comes to marketing.
“Manufacturers use marketing terms to sell their products. A night cream is a moisturizer,” Dr. Frey says. “It is often formulated to be a bit thicker, found in smaller jars, and often at a higher price point than a conventional facial moisturizer, but there are no specific ingredients in ‘night’ creams that function differently depending on the time of day. Ingredients don’t know what time of day it is!”
Point being: You do not necessarily need a separate skincare routine for nighttime. As Dr. Shultz aptly puts it: “The importance [of beauty sleep] can be embellished or exaggerated, so as always, when it comes to skincare marketing, buyer beware.”