When To Use Your LED Face Mask For The Best Results
Not since gua sha has a beauty tool taken over our collective beauty routines quite like red-light therapy devices. Once viewed with a healthy dose of side-eye and some general confusion, the red-light category has gone from high-tech oddity to big business in beauty — a recent market report estimated the red-light therapy device market to be valued at $350 million in 2024, with growth expected to hit $620 million by 2031. But as more and more consumers incorporate glowing masks, wands, goggles, helmets, and panels into their skin care routines in an effort to boost collagen production, fight fine lines, and even skin tone, we’re learning that there’s still so much about this technology that we don’t know. For all that red light has been studied over the past 60-plus years, there are still new questions that come up almost daily. Case in point: When exactly is the best time of day to use your red-light therapy device?
As a beauty editor for almost two decades, I’ve watched the rise of LED devices with amused fascination. While I’ve had access to the technology for pretty much my whole career, it wasn’t until last year that I really dove into red-light therapy with any regularity (shout-out to my vibrating Therabody TheraFace Mask and my CurrentBody Skin Series 2 LED Neck & Décolletage Mask for all their hard work keeping my skin smooth and glowy). But in all my years reporting on the technology, not once did anyone mention anything about how the time of day that I was using these gadgets was at all impactful — either on my skin’s response or my body. Because according to a growing number of studies, red light isn’t just impacting your fine lines and collagen production — it’s also potentially increasing your cortisol levels and subsequently impacting your sleep habits. As someone with chronic insomnia, I’m always working to cultivate good sleep hygiene, but I’m also someone who — like most people — waits to do my red-light treatments until right before bed. The thought never occurred to me that those lights might be undoing all the hard work I was putting into crafting an ideal sleep environment.
To find out if any of this was true, I spoke with experts in LED technology, sleep, and skin to learn if it really matters what time of day you zap your skin. Read on for their enlightening (sorry, had to do it) response.
How Red Light Impacts Cortisol Levels
Considering how long scientists have been conducting clinical tests on red light therapy and its effects on the skin — since Hungarian physician Endre Mester first zapped mice in 1965 with his custom ruby laser in an attempt to destroy implanted tumor cells but wound up healing their incision scars instead, accidentally discovering photobiomodulation (PBM) in the process — we still know surprisingly little about how red light actually affects the body. Or, for that matter, what the best practices are for using it. We know our skin should be clean, we know we should be using wavelengths between 630 nanometers and 680 nanometers, we know red light is good for fine lines and wrinkles, we know blue light is good for acne… and that’s about all we know for sure.
But studies have been popping up in recent years investigating potential links between red light and cortisol production. Cortisol, the hormone responsible for helping your body get ready for sleep (among many other things), has been shown to be stimulated by exposure to red light, leading some researchers to believe that when you are using your light-therapy devices could actually make a difference in your sleep quality. “Cortisol stimulates your mind — it raises your blood pressure, raises your blood sugar,” says Alison Gracom, PA-C, who specializes in endocrinology and internal medicine at Complete Care Medical Spa in Irvine, California. “It’s what’s responsible for getting you up and ready and going for the day. If you had too low of cortisol, you wouldn’t wake up in the morning. On the other hand, if your cortisol is spiking at night, your mind is more active, and you’re going to have more trouble going to sleep or be pulled out of sleep more often.”
Typically, your cortisol is at its highest level in the morning when you wake up, and it drops to its lowest levels late at night when you fall asleep, notes Gracom. This is part of a healthy circadian rhythm which also includes production of the hormone melatonin. But scientists are finding that artificial light sources are interfering with those natural hormone production cycles — we know now that blue light from our electronic devices has the ability to influence our circadian rhythm by suppressing the secretion of melatonin. But scientists are discovering that there may be a link between red light and cortisol. A 2010 study by researchers at the Lighting Research Center at Rensselaer Polytechnic Institute (RPI) exposed 12 subjects to one hour of red LED light from a light box at 625 nanometers at different intervals throughout the day. They found that while there was no significant change in cortisol levels to those who were exposed to red light during the daytime hours, when they were exposed to the red LED light at night — when their cortisol levels should have been at their lowest — the light was able to raise their cortisol to daytime levels. Which, based on this study, could mean that red LED light used late at night could have the potential to interfere with your sleep quality.
The Sleep Expert
When I reached out to Jamie Zeitzer, PhD, a professor of psychiatry and behavioral sciences at Stanford University, who specializes in how light impacts circadian rhythms, his first response to the RPI study was skepticism. “This study has had lots of issues in the past with reproducibility and there’s no good theory as to why they have the findings that they have, which makes one think that it might be kind of random — that they found stuff that may not actually be replicable,” he explains. Zeitzer notes that he has also studied the effects of red light on the circadian rhythm. “As part of my graduate thesis 30 years ago, we gave subjects really big doses of red light,” he says. “It was like living in an E-Z Bake Oven. And despite having incredibly bright red light [exposure], it did nothing to melatonin. We could affect their circadian timing, not huge effects, but we could definitely affect it. Melatonin levels didn’t change. So anything human beings would normally be exposed to in terms of red light is not going to have an impact on melatonin levels or cortisol — cortisol really isn’t impacted by it.”
As for if red light therapy devices for the skin should be used at a certain time of day, Zeitzer thinks there’s still questions that need to be asked, both from the sleep expert side and the dermatology side. “I guarantee you that even if it hasn’t been studied, if you look at different times of day, there’s going to be different effectiveness in whatever dermatologic outcomes depending on when you give that red light therapy,” he says. “If you look at any kind of function, there’s always a circadian difference. It’s whether it’s meaningful to the individual or not. And in terms of if it is directly activating cortisol, the question is how much is it activating it? Because you can have an increase, but it might not be that meaningful in the overall physiology.”
The LED Scientist
I thought that as someone who has developed some of the most popular and award-winning LED devices currently on the market, surely Lloyd Nelson, president and CEO of LED Technologies (the masterminds behind tech like the Dr. Dennis Gross DRx SpectraLite FaceWare Pro and the Lab Light Activated Beauty Acne Light Therapy Patch) would have some insight into whether or not time of day usage had an impact on either the skin or the body’s processes. So much testing, research, and development goes into the creation of devices (the legitimate ones, anyways) that if anyone would have thought of the correlation between red light and its impacts on our systems, it would be him. After taking a look at the RPI study, he definitely had some thoughts for me.
“As you read through that study, as well as other [similar] studies, it’s the amount of optical output exposure over time that you have to take into consideration,” he says. “The type of exposure that they were recording that were generating some levels of increased cortisol were dramatically higher than what you get from a traditional light-therapy treatment for skin care at any point in time. They were making quotes of 100 milliwatts output at an hour exposure, and you wouldn’t get an FDA clearance for that. For over-the-counter skin care devices, at the highest rate, they are in the 70 milliwatts range, and the treatments go from three to six minutes. So you’re not getting the level of exposure to really generate those cortisol effects.”
He also points out that outside of a laboratory setting, in the real world, it’s very difficult to switch up the time of day when you would actually use your LED device. “It’s very difficult to adjust the timing of when you’re going to be utilizing your red-light therapy because you have to use it when you have bare skin,” he explains. “So that’s going to be early in the morning before you put on all your makeup, or it’s going to be in the evening when you take all your makeup off. If you’re really trying to treat wrinkles and aging and potentially acne, you’re kind of forced to do it in the environment when you have clean skin.”
Because of the discrepancy between optical output, exposure time, and real-world usage versus what these studies demonstrate, Nelson notes that it’s difficult for LED companies to make any sort of recommendations about time of use for devices because there aren’t yet any studies that match the real-world scenarios of the devices being used and how people actually use them. Nelson does note that in the case of LED panels, which oftentimes do have a stronger optical output exposure, people should proceed with caution, because it’s possible to overexpose yourself with anything — although even then, he remains doubtful of the ability for many of those devices to even get to their advertised strength.
He gives the example of a brand claiming to deliver 100 milliwatts of optical output per centimeter — an objectively high level of red light. “With a panel that you stand in front of, you are basically losing about 20% of optical output for every 3 inches you’re away from that panel. So most people stand in front of those panels 6 to 8 inches away, and they’re going to get maybe 50 milliwatts of optical output. The only way they’re going to get 100 milliwatts is if they’re laying on that panel naked, because light doesn’t go through clothing.” There’s a visual for you.
The Dermatologist
Finally, I reached out to board-certified dermatologist and the brains behind MMSkincare, Dr. Ellen Marmur, M.D. After using LED in her practice for years and reading clinical data on the efficacy of not just red and blue lights but amber and green as well, she created her award-winning MMSphere device, which uses five wavelengths of LED light. I expected some variation of the “time of use isn’t the most relevant” conversation, but Marmur surprised me. “So many circadian-rhythm pathology syndromes where people can’t sleep are people who are just kind of leading a stressed-out life, and they want to just have wellness,” says Marmur. “That makes me think, not about cortisol, but about the hormone dopamine. And red light has really been aligned with improving dopamine stimulation, and that gives that sense of reward and well-being, which tends to have that indirect effect on calming people down, ensuring you’re not spiking hormones like cortisol.”
She notes that when you look at red light, it signals your brain to calm down from the dopamine pathway. “If you’re going to talk about red light and when to use it, you want to align with your natural process. So using red light in the morning is just counteracting the circadian rhythm of what [your body] wants to do, while using it at night is synergistic with your circadian rhythm, which is longing to calm down.” Basically, in the morning, you naturally want to be energized, and red light is telling your body to chill out, meaning it’s better suited as a nighttime treatment, when you naturally want to wind down.
As far as cortisol goes, she notes that it’s important to remember that there are two different types of cortisol spikes in your body — the natural boost you get in the morning that wakes you up for the day and the “oh crap, everything is too much, I hate it here” instant spike you get when faced with stressful situations. Hey, they don’t call it the stress hormone for nothing. “Low-level light-therapy devices can maybe help with your stress cortisol, but not the innate circadian-rhythm cortisol,” says Marmur. “If you think of this big wave of cortisol in the morning, it is so ingrained and regulated. Just like your menstrual cycle, these things are biologically patterned, and it is very hard to change those patterns. I would think it’s the smaller day-to-day stress cortisol that you could use low-level light therapy to help reduce those spikes, and that might help your insomnia. Like, if you exercise after work, some people say they can’t go to sleep right away, or you were studying in front of a big blue computer screen and need to wind down. These are the moments where I believe optical LED could benefit you within an hour of using it.”
But it’s not just red light that has an effect on your body, notes Marmur. Blue and green LED can also have an effect on your systems, she notes. “Blue light and green light are both energizing, awakening, memory stimulants, so there is a biopsychological benefit to that. I teach people how to use the MMSphere as if it’s a stoplight: green in the morning, red at night. Amber is known for its use against seasonal affective disorder (SAD) — it’s the happy light. Green is the one that we did genomic studies on with real women and showed that it increased the mitochondria in the fat and the skin, can increase collagen, and reduces two types of bad inflammation. So green to me, it’s a grow light. And blue light is the bacteria light — it kills the acne bacteria on the skin.” She says those three colors are best done before 2 p.m., and to start doing red light around 8 p.m.
The Verdict
While there is no conclusive evidence that says using red light at night directly impacts your sleep, there also isn’t necessarily conclusive evidence that demonstrates it has absolutely zero effect either. Basically, we don’t know what we don’t know. Marmur notes that the studies that currently exist have raised some interesting questions, but tell us that we need more conclusive data. “[The RPI] study is really just a suggested study for a better study that needs to be done in the future,” she explains. As interest grows in LED therapy, both in beauty and the medical community, we need more scientists to do studies with easily reproducible results that investigate how different LED lights done at different times of day affect our cortisol and dopamine production. Only then will we truly know if there’s a better time of day to do your LED therapy.
As for what to do now, Nelson points out that LED devices are only as effective as the user is consistent with them, meaning the best time to use yours is when you can be sure you’re going to do it. While right before bed is probably not the best idea for good quality sleep, says Gracom, if you’re able to shift to closer to 6 p.m. or 7 p.m., you’re less likely to be introducing an extremely bright artificial light source right before sleep, which has the potential to mess with your internal clock. However, Nelson notes that’s not always realistic, depending on your daily routine. “If people want to change their routine and their routine now is to come home from work, immediately clean the face, do light therapy, and then if you’re going back out, get re-made up again. Honestly, I don’t think that’s ever going to happen — no one wants to do double makeup.” Fair point.
Until we hear differently, focus on doing what works for your schedule and aim to be consistent with your LED therapy. The technology continues to evolve, which means the science will follow — and we’ll know for sure when it’s really the best time to get glowing.