Photobiomodulation therapy (PBM) is a treatment that uses specific wavelengths of red and near-infrared light to stimulate cellular repair and reduce inflammation. The light penetrates skin and tissue, where it’s absorbed by mitochondria, the energy-producing structures inside your cells, triggering a chain of biological effects that can accelerate healing, ease pain, and improve tissue function. It’s painless, non-invasive, and used across a surprisingly wide range of medical fields, from wound care and dentistry to brain health and ophthalmology.
You may have also seen it called “low-level laser therapy” or “cold laser therapy.” The name was officially changed to photobiomodulation because the old terminology was misleading: lasers turned out not to be necessary (LEDs work too), “low-level” was vague, and the therapy can both stimulate and inhibit biological processes depending on the dose. The term PBM is now the standard in medical literature.
How Light Triggers Cellular Energy Production
The core mechanism centers on a specific protein inside your mitochondria called cytochrome c oxidase (CCO). This protein sits at a critical point in the chain of reactions your cells use to produce ATP, the molecule that fuels virtually every cellular process. CCO’s job is to transfer electrons to oxygen molecules, creating a proton gradient that drives ATP production.
Here’s where light comes in. A molecule called nitric oxide naturally binds to CCO and slows it down, like a brake on the energy production line. When red or near-infrared light hits CCO, it knocks that nitric oxide loose. With the brake released, the mitochondria ramp up respiration and produce ATP faster. The freed nitric oxide also enters surrounding tissue, where it dilates blood vessels and improves local circulation. This one interaction, light displacing nitric oxide from a mitochondrial protein, sets off a cascade of downstream effects: reduced oxidative stress, changes in gene expression, and activation of signaling molecules that promote repair and dampen inflammation.
Wavelengths and the Therapeutic Window
Not all light works for PBM. The therapeutic wavelengths fall into two main bands. Visible red light in the 635 to 650 nanometer range penetrates superficial tissues and is commonly used for skin conditions, wound healing, and oral treatments. Near-infrared light, which is invisible to the eye, spans roughly 810 to 850 nanometers and 915 to 980 nanometers. These longer wavelengths penetrate deeper into muscle, bone, and even the skull, making them suitable for joint pain, nerve injuries, and brain-targeted treatments. A newer wavelength around 1064 nanometers is also being studied for deeper tissue penetration.
Both lasers and LEDs can deliver these wavelengths effectively. The choice between them depends more on the clinical goal, the area being treated, and the dose required than on any fundamental difference in the light’s biological effect.
Why Dose Matters More Than You’d Think
PBM follows what researchers call a biphasic dose response. Too little light energy and nothing happens because the minimum threshold isn’t reached. The right amount of energy crosses that threshold and stimulates healing. But too much light actually reverses the benefit, suppressing cellular activity instead of boosting it. This concept dates back to a late-19th-century pharmacological principle: weak stimuli accelerate biological activity, moderate stimuli optimize it, and excessive stimuli shut it down.
This is why PBM dosing involves multiple variables, not just “how long do you hold the light on your skin.” Clinicians account for wavelength, power density (measured in watts per square centimeter), total energy delivered (measured in joules), the size of the treatment area, and whether the light is continuous or pulsed. Getting these parameters right is one of the biggest challenges in the field, and it partly explains why study results sometimes conflict. Two trials using the same wavelength can produce opposite results if the energy delivered was significantly different.
Wound Healing and Skin Repair
Some of the strongest evidence for PBM comes from wound healing research. In a study on dermal wounds in mice, animals treated with red laser light at a standard therapeutic dose showed a 4.4-fold increase in total collagen production by day five compared to untreated controls. By day ten, collagen levels were still nearly three times higher in the treated group. Collagen is the primary structural protein in skin, so this kind of increase translates directly to faster wound closure and stronger scar tissue.
Beyond wounds, PBM is used in dermatology for skin rejuvenation, hair loss treatment, and targeted fat reduction procedures. The underlying mechanism is the same: stimulating cellular metabolism in the treated area to accelerate natural repair processes.
Pain and Musculoskeletal Conditions
PBM is widely used for chronic and acute pain conditions, particularly those involving tendons, joints, and nerves. Treatments for tendinopathies, osteoarthritis, and nerve injuries have all shown benefit in clinical research. The pain-relieving effect comes from multiple pathways: reduced inflammation at the tissue level, improved local blood flow, and direct effects on nerve signaling.
In dentistry, PBM reduces pain after orthodontic appliance placement and speeds bone remodeling during treatments involving implants. Patients receiving PBM after dental implant surgery experience reduced swelling and faster healing times. It’s also used to treat recurrent mouth ulcers, where one study found that low-level laser therapy produced a statistically significant reduction in pain scores within three days compared to a standard topical paste.
Brain Health and Cognitive Function
One of the more remarkable applications is transcranial PBM, where near-infrared light is applied to the scalp to reach brain tissue. Because near-infrared wavelengths can pass through the skull, they’re able to stimulate mitochondrial activity in neurons directly. This improves cerebral blood flow, increases blood oxygen levels, and boosts the energy supply that neurons need to function normally.
In animal models of traumatic brain injury, transcranial PBM decreased inflammation and neuronal death, increased the expression of growth factors in the hippocampus (a brain region critical for memory), and promoted the proliferation of neural progenitor cells. One study found that microglial activation, a marker of brain inflammation, was significantly reduced within 48 hours of treatment. Early human studies in Alzheimer’s disease patients have shown improved cerebral blood flow and lower dementia scores. Research also shows benefit in severe depression and Parkinson’s disease, though these applications are still being refined.
PBM appears to help the brain clear amyloid-beta, the protein that accumulates in Alzheimer’s disease. Research has found that treatment accelerates amyloid-beta degradation while reducing its accumulation and suppressing the inflammatory immune response around plaques, subsequently improving cognitive function in animal models.
Other Clinical Applications
The range of conditions being treated with PBM continues to expand. In cancer care, PBM has been used to prevent oral mucositis, the painful mouth sores that develop during chemotherapy and bone marrow transplantation. A randomized clinical trial demonstrated its effectiveness for this use, and it’s become one of the better-established applications in supportive oncology.
Research on diabetes has reported striking results, with some studies suggesting PBM can reduce insulin levels by nearly three-quarters or allow patients to discontinue medication for up to six months, though these findings need to be understood as preliminary and likely specific to certain patient populations and treatment protocols. Studies on bone healing have shown that PBM-treated cells produce at least twice the calcium deposits of untreated cells after two weeks, suggesting a role in fracture repair and bone regeneration. Spinal cord injuries represent another area of active investigation.
FDA Status and Practical Access
PBM devices have received FDA clearance for several uses. In 2024, the FDA authorized a light therapy device for treating dry age-related macular degeneration, making it the first non-invasive treatment cleared for that condition. It’s worth noting the distinction: FDA “clearance” means the agency considers the device reasonably safe and effective for its intended use, but it’s a lower regulatory bar than formal FDA “approval,” which requires more extensive clinical trial data.
PBM is offered in clinical settings by physicians, physical therapists, chiropractors, and dentists. Consumer-grade devices, typically LED panels, caps, and handheld units, are also widely available, though their power output is generally lower than clinical devices. If you’re considering a home device, the wavelength and power specifications matter far more than brand claims. Look for devices that specify their wavelength in nanometers and their power density in milliwatts per square centimeter, as these are the parameters that determine whether the light will actually reach the target tissue at a therapeutic dose.