Red light therapy guide

What is red light therapy? How it works, the wavelengths, and what the research shows

Red light therapy is the use of low-intensity red and near-infrared light, delivered by LED arrays at home or by low-power lasers in some clinics, directed at the skin for a measured length of time. Researchers call it photobiomodulation, and their work examines what happens when cells absorb that light.

This guide covers the mechanism researchers describe, how to read a specification sheet, what controlled studies report and where the evidence is thin, and how Clearlight towers, Lumaflex flexible panels and the red light built into Finnmark's Trinity saunas differ in practice.

What red light therapy is, and how it works

One technique, several names

"Red light therapy" is the consumer term. Scientists call it photobiomodulation (PBM), and a 2017 review by Michael Hamblin in AIMS Biophysics notes that it is also known as low-level laser therapy; older papers use that name or low-level light therapy, both abbreviated LLLT. "Low-level" separates these devices from the high-power surgical and cosmetic lasers used to cut or ablate tissue. Early research relied largely on lasers; every device in this guide uses arrays of light-emitting diodes (LEDs).

What happens when cells absorb the light

Light can only influence tissue that absorbs it. Hamblin's review identifies the primary light-absorbing molecule, or chromophore, as cytochrome c oxidase: the final enzyme in the mitochondrial respiratory chain, which cells use to generate ATP, their energy currency. The review lists secondary effects of that absorption that include "increases in ATP, a brief burst of reactive oxygen species, an increase in nitric oxide, and modulation of calcium levels." In plain terms, that is more cellular energy, a short pulse of reactive molecules that cells also use as signals, more of a messenger molecule involved in regulating blood vessels, and shifts in calcium, another internal messenger.

Two cautions apply. Much of this mechanistic work comes from cell cultures and animal models, and a measurable change inside a cell is not the same as a noticeable result in a person. The size of any effect depends on wavelength, dose and tissue, which is why the next two sections matter.

Red light therapy wavelengths: red versus near-infrared

Wavelength, measured in nanometers (nm), determines what the light looks like and how far it travels into tissue before it is absorbed. Most devices combine two bands.

Visible red: about 620 to 700 nm

Red is the long-wavelength end of the visible spectrum, and most devices emit between 630 and 660 nm. It is absorbed relatively close to the surface, in the skin and the tissue just beneath it, so it is the band most associated with skin.

Near-infrared: beyond about 700 nm

Near-infrared begins just beyond visible red. Devices commonly use 810 to 850 nm, and some reach 1064 nm. It travels further into tissue before it is absorbed; ICNIRP describes near infrared (IR-A, 780 to 1,400 nm) as penetrating the skin to a depth of several millimeters. Because the eye barely registers it, near-infrared LEDs can look dim or faintly red while working normally.

A 2013 dermatology review by Avci and colleagues in Seminars in Cutaneous Medicine and Surgery observed that although skin is exposed to light more than any other organ, it "still responds well to red and near-infrared wavelengths." Every device in this guide uses both bands. Clearlight splits the LEDs on each of its red light therapy towers 50/50 between 650 nm red and 850 nm near-infrared. The Lumaflex Essential and Body Pro Kit pair 630 nm with 850 nm, and the Lumaflex Essential Pro carries six wavelengths: 630, 660, 810, 850, 904 and 1064 nm. Extra wavelengths widen spectral coverage; they are a design choice, not a measure of quality.

Dose basics: irradiance, distance and session time

Devices with identical wavelengths can deliver very different amounts of light. Three variables set the dose.

Why more is not automatically better

A 2009 review in Dose-Response by Huang and colleagues describes a biphasic dose response frequently observed in this field, in which low levels of light often had a much better effect on the tissue studied than higher levels; the authors note that the so-called Arndt-Schulz curve is commonly used to describe it. Doubling a session or halving the distance is therefore not a shortcut, and it may move a session past the range where effects were observed.

Manufacturer guidance ties session length to distance. Clearlight's towers offer presets from 5 to 30 minutes, and the Personal Tower's manual pairs 10 to 15 minutes at 6 to 10 inches with 20 to 30 minutes at 12 to 18 inches. Lumaflex panels, worn against the skin, run a fixed 10-minute session. Follow the guidance for your own device, not a number borrowed from another one.

What the research has examined

Photobiomodulation has a large but uneven research literature: studies differ in wavelength, light source, dose, schedule, size and quality.

Skin

A 2014 trial by Wunsch and Matuschka in Photomedicine and Laser Surgery enrolled 136 volunteers in a prospective, randomized, controlled study, and 113 of them received polychromatic light in the 611 to 650 nm or 570 to 850 nm range twice a week. Compared with controls, those participants showed significant improvements in skin complexion and skin feeling, in skin roughness measured by profilometry, and in collagen density measured by ultrasound.

The limits matter as much as the findings: it is a single trial, it used polychromatic light sources rather than the devices in this guide, and its outcomes concern skin only. The Avci review concluded in similarly measured terms: "The noninvasive nature and almost complete absence of side effects encourage further testing in dermatology."

Pain, joints and other areas

Researchers have also studied red and near-infrared light in musculoskeletal pain. Our Clinical Trials library summarizes individual studies, including a research summary on 630 nm red light and chronic pain, a study of LED light and low back pain in nurses, and a study of red and infrared LEDs and jaw-joint (TMD) pain. Protocols, doses and study quality vary widely between them, and none is a claim about what a particular device will do for you.

Red light therapy devices for home use

The devices in this guide come in three forms: towers you sit or stand in front of, flexible panels you strap to one area, and panels built into a sauna cabin. Sauna Republic carries all three, from Clearlight, Lumaflex and Finnmark.

Towers

The Clearlight Full Body Red Light Therapy Tower is the whole-body option. It ships with a fixed wall mount, with a floor stand, adjustable wall mount or adjustable door hanger as alternatives. The Personal Tower, on its included stand or an optional mini wall mount, covers one area at a time and is no substitute for a full-size tower if whole-body sessions are the goal. All three towers share the same wavelengths and published irradiance; our Clearlight red light therapy tower guide compares them, and the range is in the Clearlight towers collection.

Flexible panels

Each Lumaflex panel is a flexible silicone pad that straps around a shoulder, knee or lower back, against the skin. The Body Pro Kit adds IP67 waterproofing and a second battery, and the Essential Pro adds wavelengths. A panel trades whole-body coverage for close contact and portability. Our Lumaflex red light therapy buying guide matches each panel to a user, and every model is in the Lumaflex collection.

Built into a sauna

The Finnmark FD-4 Trinity and FD-5 Trinity XL are hybrid saunas with a red light panel built into the cabin, alongside Finnmark's infrared heaters and a Harvia traditional heater, so you can switch between heat types. Finnmark lists one wavelength for the panel, 650 nm red, and no near-infrared band like the 850 nm LEDs in Clearlight's towers, so compare it on wavelength and coverage as you would any other device. Both are in our hybrid sauna collection. The colored mood lighting many saunas include is a different feature; our chromotherapy guide explains what it can and cannot do.

How to choose

Red light therapy and your infrared sauna

Among Clearlight's towers, Clearlight designs only one to attach inside its saunas: the Clearlight CORE Red Light Therapy Tower. Its included door mount fits Clearlight Sanctuary, Premier and Outdoor cabins. Plan the electrical side first: at 200 watts, the CORE pushes most Clearlight models past their default circuit amperage when run inside an energized sauna, so Clearlight publishes a circuit upgrade for the affected models. Review it with a licensed electrician; our Sanctuary vs Premier comparison lists each cabin's stock electrical requirements.

Clearlight says the Full Body tower "is not designed to attach to your Clearlight sauna (use the CORE Tower.)" For the Personal tower, Clearlight's manual describes tabletop or stand use, while its product FAQ says it "can be conveniently mounted inside any of our Clearlight saunas." Clearlight's manual also says its red light products should be installed only where ambient temperatures do not exceed 145°F (63°C), and that higher temperatures "will result in reduced life, lumen output." Lumaflex describes its IP67-rated Body Pro Kit as water- and heat-resistant, and its sauna guide covers wearing it during a session; the Essential and Essential Pro are sweat-resistant, not waterproof, and are for use outside the cabin. The tower guide details CORE mounting and the model-by-model circuit changes.

If you would rather have the light built in, the Finnmark FD-4 Trinity and FD-5 Trinity XL, described above, include a 650 nm panel inside the cabin, so there is no separate device to mount.

Safety basics before your first session

These precautions apply to every device in this guide.

Red light therapy at home or in a business

At home, the choice comes down to space and routine: a Full Body tower for a recovery room or home gym, a Personal Tower for a desk or nightstand, a Lumaflex panel for use anywhere. HSA or FSA payment may be available at checkout, with eligibility verified per purchase; our HSA and FSA page explains the process.

A business adds questions of throughput, staffing, cleaning between clients and commercial warranty terms. Clearlight's towers carry a five-year warranty covering residential and commercial use. Our guides to Clearlight red light towers for facilities and Lumaflex panels in commercial settings cover planning in detail.

Frequently asked questions

Browse the full red light therapy collection to compare towers and panels side by side.

Clearlight, CORE, Sanctuary and Premier are trademarks of Sauna Works, Inc., dba Clearlight Infrared. Sauna Republic is an authorized Clearlight dealer. Finnmark and Harvia are trademarks of their respective owners. This article is for educational purposes and is not medical advice. Clearlight describes its products as general wellness products; their statements have not been evaluated by the FDA, and they are not intended to diagnose, treat, cure or prevent any disease. If you are pregnant, photosensitive, taking medication, or managing a medical condition, consult a healthcare professional before using any light therapy device, and follow the manufacturer's safety guidance.