Red and near-infrared light therapy are the most widely used and studied forms of light therapy for pain relief. These wavelengths, typically between 630 and 850 nanometers, penetrate skin and muscle tissue to reduce inflammation and promote cellular repair. A newer approach using green light is also showing promise for headaches and nerve-related pain, though it works through an entirely different biological pathway.
Red and Near-Infrared Light
Red light, centered around 660 nanometers, and near-infrared light, centered around 810 to 830 nanometers, are the two wavelength ranges with the strongest evidence for pain relief. These fall under a broader treatment category called photobiomodulation, sometimes still referred to as low-level light therapy or cold laser therapy. The key difference between the two is how deep they reach. Red light at 660 nm is absorbed by blood and skin components, limiting its penetration to less than 10 millimeters. Near-infrared light at 810 nm passes through those surface layers and can reach 30 to 40 millimeters or deeper, making it better suited for joint pain, deep muscle soreness, and conditions below the skin’s surface.
Not all wavelengths in this range work equally well. Research has identified two “sweet spots” that align with absorption peaks in a specific enzyme inside your mitochondria: around 665 to 670 nm and 810 to 830 nm. Light at 730 nm, which falls between these two peaks, has been shown to be largely ineffective. So if you’re evaluating a device, the specific wavelength matters more than whether it simply falls somewhere in the red or infrared spectrum.
How Light Reduces Pain at the Cellular Level
The primary target of red and near-infrared light is an enzyme in your mitochondria called cytochrome c oxidase. This enzyme is the last step in the chain that produces ATP, your cells’ energy currency. Under stress or inflammation, a molecule called nitric oxide binds to this enzyme and slows down energy production. When red or near-infrared photons hit the enzyme, they knock that nitric oxide loose, restoring normal energy output. Cells in the treated area produce more ATP, which fuels repair processes and helps resolve inflammation faster.
This also explains why light therapy works best on tissue that’s inflamed or damaged. In healthy, unstressed cells, the effect is minimal. In cells under oxidative stress, photobiomodulation has been shown to restore the mitochondrial membrane potential back toward normal levels while reducing harmful reactive oxygen species. The result is less inflammation, less swelling, and less pain signaling from the affected area.
Green Light for Headaches and Nerve Pain
Green light exposure is a distinct approach that doesn’t work by penetrating tissue at all. Instead, it acts through the eyes. Specialized light-sensing cells in the retina respond to green light and trigger a chain of signals through the brain that ultimately modulates pain-processing regions. Animal studies have shown that green light activates the body’s endogenous opioid system, the same internal pain-relief network that prescription painkillers target.
In one clinical case, a patient with chronic daily headaches who used green light-emitting diode exposure reported a drop in average headache severity from 6 out of 10 to 3 out of 10. The treatment typically involves sitting in a room lit only by a green LED light source for one to two hours daily. While the evidence base is still smaller than for red and near-infrared therapy, the mechanism is biologically plausible and the approach is low-risk.
Conditions Where Light Therapy Helps
Arthritis is one of the best-studied applications. In a study of 25 patients with rheumatoid arthritis treated with 820 nm near-infrared light, 72 percent reported pain relief in their hands. Photobiomodulation has also been studied for osteoarthritis of the knee, where its anti-inflammatory effects can reduce swelling comparably to corticosteroid treatment when the right dose is used.
For exercise-related muscle damage, light therapy offers modest but measurable benefits. In one controlled study, participants who received phototherapy after intense calf exercises reported peak soreness of 1.0 out of 10 at 24 hours, compared to 2.3 out of 10 in the untreated group. Soreness also returned to baseline about a day faster. The effect was most noticeable in the first 24 to 48 hours after the muscle damage occurred, which is when inflammation peaks.
The Dose Window That Works
Light therapy follows a “Goldilocks” pattern where too little does nothing and too much can actually cancel out the benefits or become counterproductive. This is called a biphasic dose response. The energy delivered to tissue is measured in joules per square centimeter. For red and near-infrared light applied to living tissue, doses of 3 to 5 joules per square centimeter typically produce beneficial effects. Doses as high as 30 joules per square centimeter can still work, but only if delivered at the right power intensity. At 50 to 100 joules per square centimeter, the therapeutic effect disappears and may even reverse.
This is why more isn’t better with light therapy. In an animal study on joint inflammation, three of four dosing combinations reduced knee swelling nearly as well as a powerful steroid. The one combination that failed used the right total energy but delivered it in just one minute, far too fast. The same energy spread over 10 minutes worked. Treatment time and power intensity both matter, not just total energy.
Clinical Devices vs. Home Devices
Professional-grade devices used in clinics are typically lasers, which produce a focused, coherent beam of a single wavelength. Some use superpulsed technology, where a 905 nm laser delivers brief pulses with a peak power of around 20 watts but an average output of only 60 milliwatts. This pulsing allows deep tissue penetration without heating the surface.
Home devices almost exclusively use LEDs rather than lasers. LEDs cost roughly one hundred times less per milliwatt of output, making consumer panels and wearable wraps affordable. They can also cover a much larger area of skin at once, which is practical for treating broad regions like the back or thighs. The tradeoff is that LEDs scatter light more than lasers do, so they deliver less energy to deep tissues. For surface-level or moderately deep conditions, research has found no meaningful difference between LED and laser light at the same wavelength and dose. A 635 nm LED and a 632.8 nm laser produced equivalent healing results when matched for energy delivery.
If you’re buying a home device, look for one that specifies its wavelength (ideally in the 660 or 810 to 830 nm range), its power output in milliwatts, and whether it has been cleared by the FDA for safety. FDA clearance means the device meets basic safety standards and performs comparably to other cleared devices on the market.
Who Should Be Cautious
Light therapy at red and near-infrared wavelengths is generally considered safe, with no significant side effects reported in most studies. The main concern is photosensitivity caused by medications. Hundreds of commonly prescribed drugs can make skin react abnormally to light exposure. The most notable categories include certain blood pressure medications like hydrochlorothiazide and amlodipine, common antibiotics such as tetracyclines and fluoroquinolones, cholesterol-lowering statins like atorvastatin, and several antidepressants including fluoxetine and sertraline. Even over-the-counter NSAIDs like ibuprofen and naproxen carry some photosensitizing potential.
If you take any of these medications and are considering light therapy, the combination could cause skin reactions ranging from exaggerated sunburn to blistering. This applies more to treatments covering large skin areas than to small, targeted applications, but it’s worth checking whether your medications appear on photosensitivity lists before starting regular sessions.