Infrared light is a form of energy just beyond what your eyes can see, sitting past the red end of the visible light spectrum. It carries wavelengths from about 700 nanometers to 1,000 micrometers, making it invisible but felt as heat on your skin. What makes infrared light genuinely useful is that different wavelengths penetrate the body to different depths, triggering effects that range from warming your muscles to boosting energy production inside individual cells.
Where Infrared Fits on the Light Spectrum
Visible light, the colors you can see, spans wavelengths from about 380 to 700 nanometers. Infrared begins right where red light ends, at roughly 700 nanometers, and stretches out to 1,000 micrometers (one millimeter). That’s a huge range, and it gets divided into three practical categories.
Near-infrared (roughly 700 to 1,400 nanometers) is the closest to visible light and penetrates the deepest into body tissue. This is the type most commonly used in therapeutic devices and light panels. Mid-infrared (1,400 nanometers to about 3 micrometers) is partially absorbed by water in the skin and generates more noticeable warmth. Far-infrared (3 to 1,000 micrometers) is the type infrared saunas use. It doesn’t penetrate deeply, but it heats the body’s surface efficiently, raising core temperature and inducing sweat.
How It Works Inside Your Cells
The therapeutic effects of near-infrared light come down to something happening inside your mitochondria, the structures in every cell that produce energy. A specific enzyme at the end of the mitochondrial energy chain absorbs near-infrared photons. When this enzyme absorbs light, it speeds up, consuming more oxygen and producing more of the energy currency your cells run on. The result is that cells exposed to near-infrared light have more energy available for repair, growth, and normal function.
What makes this especially relevant for the brain is that neurons are extraordinarily hungry for oxygen-based energy. When near-infrared light reaches brain tissue (it can penetrate the skull to a limited degree), it enhances both energy production and blood flow in the targeted area. This is the basis for an emerging treatment approach where near-infrared light is applied to the forehead to influence mood and cognition.
Skin Healing and Collagen Production
Infrared light stimulates the skin cells responsible for producing collagen and elastin, the two proteins that keep skin firm and elastic. In lab studies, fibroblasts (the cells that build these proteins) ramp up collagen output within two hours of infrared exposure, and the increase is proportional to exposure time. Elastin production follows a similar pattern, rising measurably after just one hour.
This isn’t just a laboratory finding. Animal studies show greater collagen regeneration and faster infiltration of repair cells in skin wounds treated with far-infrared radiation. Multiple in vivo studies confirm that near-infrared light promotes wound healing through a combination of collagen synthesis, cell proliferation, and faster movement of the skin cells that close wounds. This is why infrared light panels are marketed for skin rejuvenation, and why some dermatologists incorporate them into treatment plans for scarring and photoaging.
Pain and Inflammation Relief
Infrared light has the most clinical evidence for musculoskeletal pain. A systematic review of infrared therapy for chronic pain found consistent decreases in pain scores across multiple conditions. For knee osteoarthritis, far-infrared emitting patches reduced pain by 12.5% after one week and 25% after four weeks. One study using a specific infrared laser wavelength reported a 60.9% reduction in pain scores for osteoarthritis patients. For chronic low back pain, infrared photo energy improved symptoms by 36%.
The pain relief likely comes from a combination of increased blood flow, reduced inflammatory signaling, and the cellular energy boost described above. Tissues with more energy heal faster and produce fewer distress signals. For people with joint pain or muscle soreness, this translates to less stiffness and greater mobility over the course of treatment.
Muscle Recovery After Exercise
Near-infrared light applied after intense exercise helps preserve muscle strength during the recovery window. In a controlled trial using near-infrared laser treatment after strenuous resistance exercise, participants who received active treatment lost 56.5% of their maximum voluntary contraction strength, compared to 60.8% in the group that received a sham treatment. That’s a modest but real difference in how quickly the muscle bounced back. The treatment did not, however, significantly reduce muscle soreness to the touch, suggesting the benefit is more about functional recovery than pain perception.
Effects on Mood and Brain Function
Applying near-infrared light to the forehead, a technique called transcranial photobiomodulation, has shown promise for depression. A meta-analysis of randomized controlled trials found a moderate improvement in depressive symptoms compared to controls. People under 40 responded more strongly than older adults, and LED-based devices outperformed lasers in the pooled data. Sessions of about 30 minutes, performed fewer than three times per week over at least 15 sessions, appeared to produce the best results. The effect is thought to work by increasing blood flow and energy metabolism in the prefrontal cortex, a brain region involved in mood regulation.
This is still a relatively new application, and no standardized treatment protocol exists yet. But the consistency of results across multiple trials suggests the effect is real, not placebo.
Infrared Saunas vs. Light Therapy Panels
These two popular uses of infrared light work through different mechanisms. Infrared saunas use far-infrared wavelengths to heat your body from the outside, raising your core temperature to induce deep sweating. Sessions typically run 20 to 40 minutes and are primarily used for relaxation, cardiovascular conditioning, and muscle relaxation. Regular sauna use can improve circulation and reduce blood pressure.
Light therapy panels use near-infrared and red wavelengths at much lower intensities. They don’t produce significant heat. Instead, they deliver light energy that penetrates tissue and triggers the cellular responses described above. Sessions are shorter (10 to 20 minutes) and target specific areas like joints, skin, or the face. If your goal is wound healing, skin health, or localized pain relief, a light panel is the more direct tool. If you want whole-body relaxation and cardiovascular benefits, a sauna is the better fit.
How to Use It Safely
Consumer infrared light therapy devices are classified as Class 2 medical devices by the FDA, meaning they carry moderate risk and require some regulatory oversight. Most people use them 2 to 5 times per week for 10 to 20 minutes per session. Going beyond 30 minutes in a single session has been associated with skin burns and blisters, so following manufacturer guidelines matters.
For eye safety, light therapy appears safe for physically healthy people who aren’t taking photosensitizing medications. Ocular complaints like discomfort or temporary vision changes occur in up to 45% of participants in some studies, but no lasting eye damage has been documented in healthy individuals. The one exception in the research literature involved a person taking a medication known to increase light sensitivity. If you’re on any medication that makes your skin or eyes more reactive to light, that’s worth checking on before starting regular sessions.
People with heat sensitivity or cardiovascular conditions should be more cautious with infrared saunas specifically, since the sustained heat exposure places demands on the heart and circulatory system that light panels do not.