Red Light Therapy: Should You Open a Window?

About the author

Evelyn Reed, M.S.

Health Science EducatorCertified Wellness Coach

Evelyn Reed, M.S., is a Health Science Educator and Certified Wellness Coach specializing in evidence-based, at-home wellness solutions. With a Master's degree in Health Science, she focuses on translating complex scientific research on cellular health and light therapy into practical, accessible protocols. Evelyn is dedicated to empowering individuals to manage pain, improve sleep, and enhance skin vitality. Her science-first, empathetic approach makes her a trusted advocate for achieving long-term health goals.

When people bring red light therapy devices into their homes, one of the first practical questions they ask me is surprisingly simple: “Should I open the window during my session, or close the blinds and create a dark room?”

It sounds like a small detail, but your light environment, airflow, and even view of the outdoors can meaningfully change how a session feels and potentially how it supports your overall wellness. In this article, I will walk you through what we actually know from research on red light therapy, sunlight, and indoor lighting, and then translate that into practical, compassionate guidance you can use in your own home.

I will stay within what current evidence supports from sources such as the Cleveland Clinic, Examine, Joovv, Kineon, and peer‑reviewed journals, and I will clearly separate science from my hands‑on, real‑world experience helping clients integrate red light therapy into their daily lives.

Red Light Therapy and Sunlight: Same Family, Different Behavior

Before we talk about windows, it helps to clarify what your body is experiencing during a red light therapy session compared with ordinary sunlight.

What Red Light Therapy Actually Does

Red light therapy, also called photobiomodulation or low‑level light therapy, uses specific red and near‑infrared wavelengths from LEDs or low‑energy lasers. The Cleveland Clinic explains that these wavelengths act on mitochondria, the “power plants” of your cells, helping them produce more energy, repair tissue, and reduce inflammation. Clinical and research reports describe benefits for skin appearance, wound healing, certain types of pain and inflammation, and even hair growth, although the evidence is stronger for some uses (like skin and hair in dermatology) than for others.

UCLA Health and the Cleveland Clinic both emphasize two key points. First, when used correctly, red light therapy appears noninvasive and generally low risk, especially compared with ultraviolet (UV) light. Second, many claims online go far beyond what studies have firmly proven. In other words, it is a promising tool, but not a magic wand.

Importantly for our window question, consumer devices are designed to deliver targeted red and near‑infrared light without UV. Lumivisage and other skin‑focused sources underline that these devices do not cause sunburn, do not tan the skin, and do not trigger vitamin D production. They sit in the “therapeutic” portion of the spectrum but intentionally leave out the UV that makes the sun both powerful and potentially risky.

What Sunlight Brings to the Session

Natural sunlight is a very different animal. It is a broad spectrum that includes red and near‑infrared, but also ultraviolet and blue light. Examine highlights that unobscured sunlight can provide roughly 20–40 milliwatts per square centimeter of red and near‑infrared light, which overlaps with the intensities used in many red light therapy studies. On paper, that means sunlight can deliver a red or near‑infrared “dose” similar to some devices.

But the overlap stops there. Sunlight also brings UV radiation. Research summarized in the journal article “Benefits of Sunlight: A Bright Spot for Human Health” makes it clear that UV exposure has a dual role. UV drives vitamin D production and may help protect against some internal cancers and illnesses when exposure is moderate and regular, yet the same UV contributes to DNA damage, skin aging, and higher risks of skin cancers with excessive or intermittent overexposure.

Several sources, including Kineon, Lumivisage, and Prism, stress that red and near‑infrared light are the “gentle healers” in the spectrum, while UV is the sharper edge of the sword. That distinction is exactly why red light therapy devices strip UV out. Sunlight can absolutely nourish health, particularly by generating vitamin D and regulating mood and circadian rhythm, but it must be handled with respect.

Examine also notes that there is very little direct research asking whether ordinary sun exposure produces the same health outcomes as structured red light therapy sessions, even though light intensities overlap. Because of that, we cannot simply assume that sitting in the sun equals a red light session.

This brings us to windows.

Red Light Therapy and Sunlight comparison: natural light (UV/IR) vs. artificial (red/NIR) wavelengths and control.

How Opening a Window Changes Your Red Light Session

When you open a window during your red light therapy session, you are changing three things at once: the type and intensity of light in the room, the air and temperature around your body, and the way the space feels psychologically. All three can matter.

Light: Device‑Only vs Device Plus Daylight

With the blinds closed and lights dim, the primary light hitting your skin and eyes during a session is from the red light device. That offers a fairly controlled environment: a known wavelength range (red and near‑infrared), no UV, and a predictable intensity.

When you open the window and let in daylight, you add a second light source. The exact impact depends on whether you are getting soft ambient daylight or direct sun on your skin and eyes.

Research summarized by Examine indicates that direct, unobscured sunlight can deliver red and near‑infrared intensities comparable to many therapy devices. Add that on top of a device and your cells may be getting a larger overall red/near‑infrared dose, plus UV and blue light. There are no clinical trials comparing “device alone” versus “device plus direct sun through an open window,” so we do not have hard numbers on combined effects. What we can say, based on physics and the published data, is that your skin and eyes are receiving more total light energy and a broader spectrum.

That is not automatically bad. Joovv and other photobiomodulation sources note that red and near‑infrared can even help cells tolerate and repair UV‑related stress. But the presence of UV and the lack of dose‑control from the sun reintroduce the very issues red light devices were designed to avoid.

If the window is open and you have only diffuse daylight without direct sun on your body, the situation is more moderate. You still gain the psychological and circadian benefits of seeing natural light, with less UV intensity on your skin. In this case, the red light device likely remains the dominant “therapeutic” stimulus, and daylight acts more as a background mood and rhythm cue.

Airflow and Temperature

The circadian‑health research summarized by GoAyo and similar sources suggests that a cool, quiet, and dark bedroom supports sleep, with a temperature around 64–66°F. Comfortable temperature matters for red light therapy too, especially if you are doing full‑body or longer sessions. Devices, pods, and beds can add some warmth to the body; an open window can help keep the room pleasantly cool or bring fresh air that simply makes it easier to relax.

I see this regularly in practice. When a room is stuffy or overly warm, clients tend to cut sessions short or feel restless. When they have a bit of fresh air, they are more likely to complete the recommended time and actually enjoy the process, which matters for consistency over weeks and months.

Psychological Environment: Light, View, and Mood

There is another dimension that is less about mitochondria and more about mental health. Multiple sources, including Healthline and UCLA Health, highlight that natural light improves mood, reduces stress, and supports better sleep. Large workplace surveys show that access to daylight and views is often the most valued feature of an office, beating out gyms or free coffee.

UCLA Health also reports that each additional hour spent outdoors in natural light was associated with lower long‑term depression risk and reduced use of antidepressant medications. Even without going outside, Healthline notes that increasing natural light indoors can support vitamin D status and mood.

When you open the window or at least open the shades during a red light session, you bring some of that psychological benefit into the experience. You see the sky, trees, or neighborhood rather than just a dark wall. For many people, this makes sessions feel less clinical and more like a nourishing ritual. That matters, because red light therapy is not a one‑time procedure; it usually requires repeated, consistent use over weeks.

Red light therapy session with open window improving airflow & comfort, closed window traps heat & CO2.

Window Open vs Closed: Key Differences in One View

Here is a concise comparison of how window status can shape a typical at‑home session.

Factor	Window Closed (dim room)	Window Open with Daylight
Light spectrum on skin	Primarily red and near‑infrared from device; no UV	Device light plus broad‑spectrum daylight; may include UV and blue if direct sun reaches skin
Light to the eyes	Mainly red device glow and any indoor lighting	Bright natural light to the eyes, which supports circadian rhythm and mood, especially earlier in the day
Control of dose	Highly controlled; device output dominates	Less controlled; sunlight intensity varies by time of day, season, weather, and angle
Vitamin D	No vitamin D production from device alone	Potential vitamin D synthesis if direct sun reaches skin; Healthline notes that sunlight exposure indoors or outdoors can contribute
Thermal comfort	Depends on room ventilation and device warmth	Fresh air can help keep you cool and comfortable, especially with larger full‑body devices
Safety profile	No UV‑related sunburn risk from device itself	Reintroduces UV risk if direct sun is strong and sessions are long or skin is sensitive

This table is not meant to declare one option “good” and the other “bad.” Instead, it shows where opening a window meaningfully changes the environment so you can make informed choices.

Benefits of Opening a Window During Red Light Therapy

When used thoughtfully, opening a window during red light therapy can offer real advantages, especially for circadian health, mood, and overall light hygiene.

Supporting Circadian Rhythm and Sleep

Circadian‑health experts emphasize that light is the master signal for your internal clock. Joovv and GoAyo both describe how morning light entering the eyes communicates with the brain’s master clock in the suprachiasmatic nucleus, helping synchronize hormones like cortisol and melatonin. The Huberman Lab newsletter recommends viewing outdoor morning sunlight within the first one to two hours after waking to anchor circadian rhythm, improve energy and focus, and set up better sleep later that night.

Ideally, that morning light exposure happens outside rather than through glass, because windows change both intensity and spectrum. However, for many people with tight schedules or harsh winter weather, stepping out is not always realistic during every red light session. In those cases, opening a window or at least sitting near a bright window while using your device can be a pragmatic compromise that brings more natural light into your eyes compared with a dark or artificially lit room.

If you use your red light device in the morning, pairing it with an open window can be especially synergistic. The red and near‑infrared wavelengths support cellular energy and recovery, while the daylight streaming in works on your circadian system and mood. You are essentially layering a targeted therapy on top of a foundational circadian habit.

Mood, Stress, and Motivation

Healthline and UCLA Health both connect natural light exposure with improved mood, lower stress, and higher happiness. Lack of daylight in workplaces has been associated with disrupted sleep hormones, more depressive symptoms, and lower productivity. On the flip side, deliberate daylight exposure, even during short breaks, has been linked with better mood and energy.

When clients struggle to stick with their red light routine, making the space more uplifting often helps. Opening the window, letting in some natural sounds, and seeing the outdoors can transform the session from “another task on my to‑do list” into a few minutes of mindful downtime. That shift is subtle but powerful. People are more likely to keep up a habit that feels pleasant, not just “healthy.”

Fresh Air and Comfort

There is less formal research on ventilation during red light therapy specifically, but the broader sleep and wellness literature consistently points to the importance of a comfortable, slightly cool environment. Simply put, you are more likely to relax and stay present when the air feels fresh and the temperature is not overly warm.

With full‑body panels or pods, a closed room can sometimes feel stifling, especially in smaller apartments. Opening a window allows heat to dissipate and can prevent that sluggish, overheated feeling that makes some people abandon sessions early.

Benefits of opening a window during red light therapy: improved air, reduced heat, enhanced relaxation.

Potential Drawbacks and Safety Concerns With Open Windows

Opening a window is not automatically better. Depending on how and when you do it, it can introduce some real downsides.

UV Exposure and Skin Health

Multiple sources agree on one point: direct sun exposure carries UV‑related risks. Kineon, Prism, Lumivisage, and the peer‑reviewed sunlight article all describe how UV can cause sunburn, accelerate wrinkles and age spots, and increase skin‑cancer risk over a lifetime. The same research notes that moderate, regular sun exposure brings major health benefits, including vitamin D production and potentially lower all‑cause mortality, but the pattern and dose of UV exposure matter.

If you position yourself so that direct midday sun pours through an open window onto your skin during a session, you are no longer just doing a UV‑free red light treatment. You are essentially combining photobiomodulation with a short sunbathing interval. For some people, that might be acceptable, especially if the session is brief and skin is not prone to burning. For others, especially those with fair skin, a history of skin cancer, or photosensitive conditions, it could be problematic.

One practical nuance from Examine is worth highlighting: most conventional sunscreens are formulated to block UV while allowing much of the red and near‑infrared light to pass through. A minority of sunscreens also block some red and infrared. That means that if you do end up in mild sunlight during a red light session and you wear a typical UV‑blocking sunscreen on exposed areas, you are likely still getting most of the therapeutic red and near‑infrared photons from your device while reducing UV harm. Always check your specific product, and remember that sunscreen is just one layer of skin protection alongside time‑of‑day and clothing choices.

Dose Control and Uncertainty

Red light therapy devices are designed with a certain intensity and recommended session length. The evidence we have, limited as it is, is based on those parameters. When you add an unpredictable light source like the sun, your total dose is no longer known, and we do not yet have large trials to tell us how combined exposures behave.

Examine explicitly cautions that, even though sunlight’s red and near‑infrared intensities overlap with device settings, there is little direct research proving that ordinary sun produces the same health effects as structured red light therapy. The mix of UV, blue, and other wavelengths can enhance or counteract potential benefits. In real‑world conditions, heavy sun exposure tends to promote overall skin aging, even if red and near‑infrared portions might be mildly protective.

As a wellness practitioner, I translate that into practical humility. If your goal is to follow a protocol supported by existing studies as closely as possible, leaning toward a more controlled light environment, especially for skin concerns, makes sense. That often means minimizing strong direct sunlight during the actual red light exposure and getting your sun dose at another time of day.

Timing and Sleep

Timing matters. Huberman’s light guidance, based on circadian science, is clear that bright light exposure late at night, especially overhead or screen light between roughly 10:00 PM and 4:00 AM, can suppress melatonin, lower dopamine, and worsen mood and metabolic health. Red light is less disruptive than blue‑rich white light, which is why he and others use dim red bulbs in the evening, but intense light at the wrong time still has the potential to push your clock later.

For evening red light therapy sessions, opening a window is usually not a problem if it is already dark outside. In that case, you get fresh air without extra bright light. However, if you live in an area with strong bright outdoor lighting or you like to do sessions very late in a brightly lit room with windows uncovered, you may want to reconsider. Supporting melatonin and sleep generally means minimizing bright, white, or blue light in the late evening, regardless of whether it enters through a window or a ceiling fixture.

Open window risks: fall, burglary, insects, weather damage. Important for red light therapy safety.

Making a Thoughtful Choice for Your Home Sessions

There is no single “right” rule about windows that applies to everyone. Instead, I encourage you to think in terms of purpose, timing, and personal sensitivity.

If your primary goal is skin rejuvenation or a specific dermatologic concern and you want your routine to mirror published studies as closely as possible, a more controlled environment is reasonable. That would mean limiting direct sun on the treated area during the session, keeping room lighting modest, and focusing the light exposure on your device. You can still open the window slightly for fresh air if the sun is not directly streaming in.

If your main priorities are mood, energy, and circadian health, and you live in a place where you rarely get outside, combining morning red light therapy with an open window and visible daylight may be a smart, efficient habit. You get bright natural light to your eyes, which studies from UCLA Health, Healthline, and circadian researchers show is linked to better mood and sleep, while your device provides targeted red and near‑infrared support to your skin, muscles, or joints.

In both cases, be mindful of UV risk. Research from sunlight and photobiology experts suggests that moderate, regular light exposure supports health, while burns and intense intermittent overexposure cause most of the trouble. If you notice redness or irritation from sunlight during or after sessions, adjust your positioning, shorten the time in direct sun, or shift to earlier or later in the day when UV is lower.

Finally, remember that your environment should support your nervous system as well as your cells. If a fully dark room feels claustrophobic or clinical, let in some daylight or at least crack the window to hear outside sounds. If outdoor noise or streetlights feel distracting, gently closing blinds while still maintaining some airflow can make your sessions more peaceful. Consistency over months is far more important than chasing a theoretically perfect setup.

Woman reading on sofa, making thoughtful choices for home red light therapy in a sunlit room.

FAQ: Common Questions About Windows and Red Light Therapy

Does opening a window make my red light therapy session more effective?

Opening a window does not automatically make a session more or less effective in a simple way. It changes the light mix, adding daylight that may contain red and near‑infrared intensities comparable to some therapy devices, as Examine notes, but it also introduces UV and blue light. For mood and circadian support, daylight to the eyes is clearly beneficial, especially in the morning. For targeted skin outcomes, the advantages of a controlled, UV‑free environment may outweigh any added red light from the sun. There are no published trials directly comparing the two situations, so the safest approach is to match your setup to your main goal and comfort level.

Is it safe to sit in direct sunlight while using my red light panel?

Short, sensible periods of sun exposure can be healthy. Restore and other wellness sources often suggest about 10–30 minutes of sunlight per day to support vitamin D, mood, and sleep, as long as you avoid burning. However, sitting in strong direct sun during a red light session means you are combining UV exposure with photobiomodulation. Because UV carries well‑documented risks for burns and skin aging, it is wise to be cautious, especially if you have fair or sensitive skin, a history of skin cancer, or are taking medications that increase photosensitivity. If you choose to combine them, keep the sun dose modest, avoid any sign of burning, and consider using clothing or sunscreen on areas not being treated by the device.

Can I wear sunscreen if daylight is coming in during my session?

Yes. Examine notes that most conventional sunscreens are formulated to block UV while allowing much of the red and near‑infrared spectrum to pass through, although a minority of products also block some red and infrared wavelengths. That means sunscreen usually does not eliminate the potential benefits of red light therapy, whether from your device or from sunlight, while it does reduce UV damage. If your session area receives direct sun through an open window and you are concerned about burns or photoaging, wearing sunscreen on exposed skin is a reasonable protective step in addition to sensible timing and session length.

What about evening sessions—should windows be open or closed?

For evening sessions focused on relaxation, pain relief, or sleep support, the priority is usually maintaining a low‑light, calm environment that does not suppress melatonin. The Huberman Lab newsletter emphasizes avoiding bright, blue‑rich light late at night because it can worsen sleep and mood. Opening a window at night is generally fine if it is dark outside and does not introduce bright light from streetlamps or neighboring buildings. In that case, you get cooler air and fresh ventilation while the red light device provides the main light stimulus, which is less disruptive to sleep than ordinary white light.

If I work indoors all day, is it better to open my window and do red light therapy near it?

If your days are spent mostly indoors under artificial lighting, you are in the same situation described by Joovv and Lumebox, where estimates suggest many Americans spend about 93% of their time inside and miss out on beneficial natural light. In that context, combining red light therapy with more natural daylight is often a smart strategy. Opening the window or sitting near a bright window during a morning or daytime session can support your circadian rhythm, mood, and potentially vitamin D status, while the device delivers its targeted red and near‑infrared effects. Just remain attentive to UV intensity and your skin’s response, and avoid turning your session into unintended sunbathing during the strongest midday sun.

Red light therapy works best when it is integrated into a thoughtful, light‑aware lifestyle rather than used in isolation. Whether you prefer the calm focus of a dim room or the vitality of fresh air and daylight, your window is not just a piece of glass. It is a tool you can adjust to align your sessions with both the science of light and your own lived experience, helping you build a routine that is realistic, restorative, and truly sustainable at home.