Red Light

What is red light therapy?

Red light therapy, formally called photobiomodulation (PBM), uses wavelengths of red (620-700 nm) and near-infrared (NIR, 700-1100 nm) light to trigger measurable changes in cell behavior. The therapy doesn't heat tissue or cause UV damage. Instead, photons at these wavelengths are absorbed by mitochondria, where they kick-start a chain of biochemical reactions that boost cellular energy output. Over 5,000 peer-reviewed papers have examined PBM across dozens of medical fields, from dermatology and orthopedics to neurology ^[1].

How red light therapy works at the cellular level

The core mechanism is straightforward. Cytochrome c oxidase (CCO), the final enzyme in the mitochondrial electron transport chain, absorbs red and NIR photons. This releases nitric oxide that was blocking the enzyme, restoring normal electron flow and increasing ATP production by 20-50% in treated tissue ^[2]. The downstream effects include activation of Nrf2 (which ramps up antioxidant defenses) and modulation of NF-kB signaling (which, at low ROS levels, shifts gene expression toward anti-inflammatory pathways).

What makes PBM unusual among therapies is the biphasic dose response. Too little light does nothing. The right dose produces a strong cellular response. Too much light actually reverses the benefits, a phenomenon described by the Arndt-Schulz curve. This is why device specifications and treatment protocols matter more than most people realize.

Wavelengths and penetration depth

Red light at 630-660 nm reaches about 2-3 cm into tissue, making it best suited for skin conditions, superficial wounds, and surface-level inflammation. NIR at 810-850 nm penetrates 5-7 cm, deep enough to reach joints, muscles, bone, and even brain tissue through the skull. Most high-quality devices combine both ranges. Effective treatment parameters typically fall between 3-50 mW/cm2 irradiance and 10-50 J/cm2 energy density, applied for 10-20 minutes per area ^[3].

What the clinical evidence shows

The strongest evidence exists for skin health. A controlled trial found significant improvements in collagen density, elasticity, and wrinkle depth after 12 weeks of treatment at 633 nm, with results continuing to improve over three months of use ^[4]. For musculoskeletal recovery, NIR at 810 nm applied before exercise reduced delayed-onset muscle soreness (DOMS) by up to 50% and sped up strength recovery in multiple studies.

The FDA has authorized photobiomodulation devices for dry age-related macular degeneration. In a study of 100 patients with intermediate AMD, 53% of treated patients showed more than five letters improvement in visual acuity after two years of treatment ^[5]. For wound healing, a trial on second-degree burns found PBM cut average healing time by 46% compared to controls ^[6].

Brain health and cognitive function

Transcranial photobiomodulation at 810 nm is one of the more surprising applications. A 2024 randomized, double-blind, placebo-controlled trial found that tPBM increased both cognitive function and serum BDNF levels in adults over 50 with mild cognitive impairment ^[7]. Research is also underway for Alzheimer's disease, post-COVID brain fog, and traumatic brain injury recovery. The results are promising but still preliminary for most neurological applications.

Practical guidelines for home use

• Pick devices that list exact wavelengths (630-660 nm and/or 810-850 nm), irradiance in mW/cm2, and have independent testing. "FDA-cleared" means the device passed basic safety review.
• Keep a consistent distance from the device. Irradiance drops with the square of distance, so even a few extra centimeters reduce your dose significantly.
• Start with 10-minute sessions per treatment area. Increase to 15-20 minutes based on your response over 2-3 weeks.
• For broad systemic effects, treat large skin areas like the torso, back, or legs to maximize total photon absorption.
• Morning sessions complement natural circadian light exposure. Post-workout sessions support recovery signaling.
• Expect 3-6 weeks of consistent use (3-5 sessions per week) before seeing clear results for skin or pain conditions.
• Protect your eyes with the goggles provided. Even non-UV light at high intensity can cause retinal discomfort.