Sunlight is the richest natural source of infrared light available to you, with roughly 40 percent of the solar radiation reaching ground level falling in the infrared band.1PubMed. Near-Infrared Light and Skin: Why Intensity Matters Stepping outside on a clear day delivers far more infrared energy than most commercial devices can approximate, but how much you actually absorb depends on the time of day, the weather, what’s between you and the sky, and even the surfaces around you.
Why Sunlight Dwarfs Every Other Natural Source
The sun emits energy across a huge spectrum, from ultraviolet through visible light and deep into the infrared. At sea level on a clear day, infrared wavelengths (roughly 760 nanometers to 1 millimeter) account for about 40 percent of total solar energy, while visible light makes up most of the rest.1PubMed. Near-Infrared Light and Skin: Why Intensity Matters The near-infrared portion, sometimes abbreviated NIR, sits closest to visible red light and is the slice that biological research has focused on most heavily. It penetrates skin more easily than longer infrared wavelengths and reaches tissues beneath the surface, which is where most of the proposed health effects happen.
No other natural source comes close to the intensity the sun provides. A campfire, a wood-burning stove, your own body heat, and the warmth radiating from sun-heated soil or rock all produce infrared, but their power densities are a fraction of what direct sunlight delivers to exposed skin. If you want to maximize natural infrared exposure, outdoor time in direct sunlight is the single most effective strategy.
How Time of Day and Weather Change the Infrared You Receive
Infrared from the sun isn’t constant. The amount that reaches you varies with the sun’s angle, the moisture content of the atmosphere, and the density of any clouds overhead. Water vapor is a major player here: it absorbs certain infrared wavelengths strongly, so humid conditions at ground level can reduce infrared transmission even on what looks like a clear day. Researchers studying surface solar irradiance have noted that variability in water-vapor absorption bands at short timescales is driven largely by moisture fluctuations in the lowest layer of the atmosphere.2Quarterly Journal of the Royal Meteorological Society. Observed patterns of surface solar irradiance under cloudy and clear‐sky conditions
Clouds scatter solar radiation in a wavelength-dependent way. Thick cloud cover cuts infrared alongside visible light, but the ratio shifts: clouds tend to scatter shorter wavelengths more, so under thin or broken cloud cover, the surviving light is somewhat richer in longer wavelengths, including infrared. That said, total infrared energy still drops significantly on overcast days. If you live somewhere frequently cloudy, you’ll get meaningfully less infrared than someone at the same latitude with clearer skies.
Altitude matters too. At higher elevations, there’s less atmosphere to absorb infrared before it reaches you. And latitude plays a familiar role: the sun’s rays travel through more atmosphere at higher latitudes, reducing total energy. Tropical and subtropical regions near sea level generally deliver the most infrared per hour of outdoor exposure, but even at temperate latitudes on a clear summer day, the infrared dose is substantial.
The Morning Sunlight Angle
There’s a reason the wellness world has latched onto the idea of getting outside in the early morning, and it isn’t only about circadian rhythms. In the first hour or two after sunrise, the sun sits low on the horizon and its light passes through a long stretch of atmosphere. This path length filters out more ultraviolet light while allowing near-infrared wavelengths through in generous proportions relative to UV. The result is a period when your skin receives a relatively high ratio of infrared to ultraviolet.
Research into how infrared interacts with skin has suggested that exposure to near-infrared wavelengths before intense UV exposure may precondition the skin. One proposed mechanism is that early-morning infrared light triggers protective cellular responses that prepare skin for the harsher midday sun. This idea, sometimes called photo-prevention, frames morning infrared exposure as an evolutionary adaptation: organisms that were active in early sunlight got an infrared “warm-up” before peak UV hit.3PubMed Central. Infrared and skin: Friend or foe The evidence here is still being developed, but the general concept that morning sunlight has a different spectral character than midday light is well established in atmospheric physics.
Why Being Behind Glass Changes Everything
Ordinary window glass transmits most visible light and a fair amount of near-infrared, but modern buildings increasingly use energy-efficient glazing designed specifically to block infrared wavelengths. These coatings and laminated films exist because infrared carries heat, and keeping it out reduces cooling costs. Advanced NIR-blocking window designs have been shown to block over 90 percent of near-infrared light between 780 and 2,500 nanometers while still letting most visible light pass through.4Renewable Energy. Near-infrared blocking window based on ATO-CWO/PVB nano-lamination That’s effective thermal engineering, but it also means you aren’t getting infrared while sitting in a modern office or behind a car windshield.
Even standard double-pane windows without fancy coatings absorb a significant portion of mid- and far-infrared, though they’re more transparent to the near-infrared band that is biologically relevant. The practical takeaway is simple: if you want infrared light from the sun, go outside. Sitting next to a window delivers some near-infrared, but it’s a reduced and filtered version of what direct outdoor exposure provides. And in newer buildings with low-emissivity glass, you may be getting very little infrared at all.
Fire, Heated Surfaces, and Other Non-Solar Sources
Anything warm emits infrared radiation. That includes campfires, wood stoves, heated stone and rock, sun-warmed soil, and even the body heat of people and animals around you. The hotter the source, the shorter the peak wavelength of its infrared emission. A campfire’s glowing coals emit strongly in the near- and mid-infrared range, while your own body, at around 37°C, radiates primarily in the far-infrared band.
Historically, humans spent evenings gathered around fires, and this would have provided hours of infrared exposure at close range. The firelight reaching your face and hands from a meter or two away delivers a meaningful dose of infrared, though it’s still modest compared to standing in full sunlight. Heated stones used in traditional practices (sweat lodges, hot stone therapies, saunas) also emit far-infrared radiation. Research on far-infrared sources has explored specialty lamps and saunas that deliver pure far-infrared radiation, and fabrics woven with ceramic nanoparticles that emit far-infrared when worn against the body.5PubMed Central. Far infrared radiation (FIR): its biological effects and medical applications These aren’t “natural” in the sunlight sense, but they use naturally occurring thermal radiation principles and produce wavelengths your body has always encountered.
The distinction between near-infrared and far-infrared matters for health claims. Most of the cellular research, including the mitochondrial effects discussed below, focuses on near-infrared wavelengths between about 650 and 900 nanometers. Fire and body-temperature sources emit longer wavelengths, mostly in the far-infrared band, which penetrate less deeply but still warm surface tissues and have distinct biological effects.
What Infrared Does When It Reaches Your Body
The biological interest in infrared, particularly near-infrared, centers on what happens inside cells. Near-infrared photons are absorbed by an enzyme in your mitochondria called cytochrome c oxidase, the final enzyme in the chain that produces cellular energy. When this enzyme absorbs near-infrared light, its activity increases, and researchers have measured corresponding increases in oxygenated hemoglobin in nearby tissue. A study using 810-nanometer laser light demonstrated that the increase in cytochrome c oxidase activity was tightly coupled to a rise in local blood oxygenation, suggesting the two processes are directly linked.6Scientific Reports. Interplay between up-regulation of cytochrome-c-oxidase and hemoglobin oxygenation induced by near-infrared laser
A separate line of evidence involves nitric oxide, a signaling molecule that dilates blood vessels. Exposure to red and near-infrared light at 670 nanometers has been shown to stimulate vasodilation that is entirely dependent on nitric oxide release from the cells lining blood vessels. When the nitric oxide was chemically blocked, the light-induced vessel relaxation disappeared completely.7PubMed Central. Red/Near Infrared Light Stimulates Release of an Endothelium Dependent Vasodilator and Rescues Vascular Dysfunction in a Diabetes Model This mechanism helps explain why people sometimes report improved circulation, reduced pain, or a sense of warmth in tissues that goes beyond simple surface heating after infrared exposure.
More speculative but intriguing is a hypothesis connecting near-infrared exposure to melatonin production inside mitochondria, not the pineal-gland melatonin associated with sleep but a locally produced version that acts as an antioxidant within the cell. Researchers have proposed a framework in which infrared radiation activates this mitochondrial melatonin pathway, potentially offering a layer of cellular protection.8PubMed Central. Optimizing Brain Biology Through Near-Infrared-Induced Mitochondrial Melatonin Synthesis: A Hypothesis Paper This remains a hypothesis, not an established finding, but it illustrates how much researchers still think they’re discovering about what infrared light does in living tissue.
How Deeply Does Natural Infrared Penetrate?
One common question is whether infrared from the sun can reach deep tissues like muscle, joints, or even the brain. The answer depends heavily on the wavelength and the power level. Skin itself absorbs and scatters a lot of infrared. Research measuring NIR penetration through tissue found that at low power levels, 810-nanometer light failed to penetrate even 2 millimeters of skin. At higher power (10 to 15 watts, far above what sunlight delivers to a small skin area), between about 0.5 and 3 percent of the light reached a depth of 3 centimeters.9PubMed Central. Near-infrared photonic energy penetration: can infrared phototherapy effectively reach the human brain?
Sunlight, though intense in total, is spread across the entire body surface and across a wide range of wavelengths. The near-infrared power per square centimeter from sunlight is far lower than what therapeutic devices concentrate into a small spot. So while natural sunlight unquestionably affects your skin, the top layer of muscle, and superficial blood vessels, its ability to reach deeper structures like joints or the brain is limited compared to focused devices. That said, the skin itself is a large organ with extensive blood circulation, and effects triggered in skin cells and superficial blood vessels can have systemic downstream consequences through circulating signals like nitric oxide and oxygenated blood.
Why Indoor Life Means Less Infrared Than You Think
Modern indoor environments create something of an infrared desert. Standard LED lighting, which now dominates homes and offices, emits in a narrow band roughly between 350 and 650 nanometers. That’s the visible range and a sliver of near-UV, with no infrared component whatsoever. Incandescent bulbs, by contrast, produced substantial infrared as a byproduct of heating a filament, but they have been phased out in many countries for energy-efficiency reasons. The shift to LEDs was a net gain for electricity bills and a net loss for indoor infrared exposure.
Researchers have pointed out that life evolved under the broad spectrum of sunlight, spanning roughly 300 to 2,500 nanometers, and that modern restricted-spectrum LED lighting eliminates the longer wavelengths entirely. The concern is that this absence of infrared in artificial light may affect normal mitochondrial function, which evolved in the presence of those wavelengths.10PubMed. LED lighting (350-650nm) undermines human visual performance unless supplemented by wider spectra (400-1500nm+) like daylight Whether this represents a meaningful health gap or an academic curiosity is still being debated, but the spectral mismatch between sunlight and LED light is a measured, physical fact.
Combined with modern IR-blocking windows, the picture is stark: someone who spends all day indoors in a modern building with LED lighting and low-emissivity glass may receive almost no infrared light during waking hours. This is a genuinely new situation in human evolutionary history. For most of our species’ existence, people spent the majority of daylight hours outdoors or in structures that were essentially transparent to solar radiation.
Practical Approaches to Increasing Your Natural Infrared Exposure
The strategies here are straightforward, even if they require rethinking some daily habits:
- Get outside early: Morning sunlight, with its favorable ratio of infrared to ultraviolet, is probably the easiest win. Even 20 to 30 minutes outdoors in early morning light exposes your skin and eyes to the near-infrared wavelengths that indoor environments lack.
- Expose skin: Infrared doesn’t penetrate clothing well. Shorts, short sleeves, or rolled-up sleeves during outdoor time increase the surface area receiving infrared. This doesn’t mean you need to sunbathe; casual exposure of arms, legs, and face adds up.
- Choose open shade over indoors: If you’re trying to avoid UV, sitting under a tree or an awning outdoors still gives you scattered and reflected infrared from the sky and surrounding surfaces. Being outside in shade is still dramatically better for infrared exposure than being behind a window.
- Spend time near natural heat sources: Sitting near a campfire or fireplace, using a traditional sauna, or even relaxing on sun-warmed stone or sand provides far-infrared exposure through thermal radiation.
- Consider your windows: If you work from home and have the choice, older single-pane windows or windows without low-E coatings transmit more near-infrared than modern energy-efficient glazing. Opening a window removes the glass barrier entirely.
None of these recommendations require buying anything. The emphasis is on removing barriers between your body and sources of infrared that already exist in your environment. The sun is generating enormous amounts of infrared every day; the question is whether you’re positioned to receive it.
The Difference Between Near-Infrared and Far-Infrared Exposure
When people talk about “infrared light” for health, they’re often conflating two rather different things. Near-infrared, roughly 700 to 1,400 nanometers, is the range that has been most studied for cellular-level effects like mitochondrial stimulation and nitric oxide release. It penetrates skin reasonably well, and its primary natural source is sunlight. Far-infrared, roughly 3,000 nanometers to 1 millimeter, doesn’t penetrate much past the skin’s surface but produces a deep warmth sensation. Its natural sources include fire, heated rock, body heat, and the thermal radiation from any warm object.
Saunas marketed as “infrared saunas” typically use far-infrared emitters, which warm the body by radiation rather than by heating the air. These provide a different experience from, say, morning sunlight, which is rich in near-infrared. Both have research backing various health claims, but the mechanisms are likely distinct. If you’re interested in the mitochondrial and nitric-oxide pathways, near-infrared from sunlight is the primary natural route. If you’re interested in whole-body warming and circulation through surface heating, far-infrared from fire and heated environments is the relevant band.
Why Vegetation-Rich Environments May Offer an Infrared Bonus
Healthy green vegetation has a peculiar optical property: it absorbs most visible light for photosynthesis but reflects a large portion of near-infrared. This is so reliable that satellite sensors use the contrast between visible and near-infrared reflectance to measure how much vegetation covers a landscape. When you walk through a forest or sit in a garden surrounded by healthy plants, the surfaces around you are reflecting near-infrared light back at you from all directions. You’re not just receiving infrared from above; you’re receiving it from the canopy, the ground cover, and the leaves around you.
This reflective effect is strongest in dense, healthy canopies. A walk in a park on a sunny day puts you in a near-infrared-rich environment in ways that a walk down a city sidewalk does not, even if the sun angle is identical. Concrete and asphalt absorb near-infrared rather than reflecting it. Green spaces effectively amplify your infrared exposure by bouncing solar near-infrared around the environment, creating a kind of diffuse infrared bath that supplements the direct beam from overhead. It’s one of those subtle benefits of spending time in nature that goes beyond the psychological and the aesthetic.