Red Light Therapy Dosing Guide
Photobiomodulation follows a biphasic dose-response: too little does nothing, too much inhibits. Wavelength, irradiance, distance, and duration determine whether a panel is functional or decorative.
Wavelengths
630nm (red)
Penetrates 2-3mm. Targets skin: acne, wrinkles, scar healing, collagen synthesis. Most studied for dermatological outcomes.
810nm (near-infrared)
Penetrates 3-5cm. Reaches muscle, bone, brain through skull. Primary wavelength for transcranial PBM, deep muscle recovery, joint inflammation.
850nm (near-infrared)
Strong cytochrome c oxidase absorption. Preferred for joint pain and systemic recovery. Most panels combine 660+850nm as general-purpose.
Distance and irradiance
Irradiance (mW/cm2) drops with the inverse square of distance. Double your distance, irradiance drops to ~25%. Most manufacturers spec at 6 inches. At 12 inches expect ~25%, at 24 inches ~6%.
Skin treatments: 6-12 inches (30-100 mW/cm2). If surface feels uncomfortably warm, increase distance. Verify with a solar power meter -- many brands inflate specs by measuring at the LED surface.
Duration formula
Skin: 3-6 J/cm2. At 50 mW/cm2, that is 60-120 seconds.
Deep tissue/joints: 10-30 J/cm2. At 50 mW/cm2, 200-600 seconds (3-10 min).
Transcranial: 10-20 J/cm2 at cortex (account for ~80% skull attenuation).
Protocols
Face/skin: 630nm, 6-8 in, 3-5 J/cm2, 3-5 min daily. Results in 4-8 weeks.
Joints: 850nm, 4-6 in, 15-30 J/cm2, 8-15 min every other day. Pain reduction in 2-4 weeks.
Full body: 660/850 combo, 12-18 in, 10-20 J/cm2, 10-15 min, 3-5x/week.
Transcranial: 810nm, device against scalp. Specialized devices only (Vielight, helmet-style).
Common mistakes
Too far: 3+ feet delivers negligible dose.
Too short: 30-second sessions are sub-therapeutic.
Through clothing: fabric absorbs and scatters photons. Treat bare skin.
Eye exposure: avoid direct eye exposure. Use goggles or close eyes.