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Reviewed August 31, 2026

Red Light Therapy vs Infrared Sauna: Different Mechanisms

The word infrared appears on both product categories, which is why people assume they are two versions of the same thing. They are not related in any useful way. The wavelengths are different by an order of magnitude, the energy lands in different places, and the proposed mechanisms have almost nothing in common.

Sorting this out changes what you should expect from each.

The wavelengths are not close

The standard subdivision comes from ICNIRP, the international body that sets non-ionising radiation exposure guidance. In its statement on far infrared radiation exposure, published in Health Physics in 2006, the infrared region splits into:

  • IR-A: 0.78 to 1.4 micrometres, so 780 to 1400nm
  • IR-B: 1.4 to 3 micrometres
  • IR-C: 3 micrometres to 1 millimetre

Red light therapy devices operate at 630 to 850nm, occasionally reaching 1060nm. That puts them at the bottom of IR-A and in visible red just below it.

Infrared saunas operate in IR-C. Carbon and ceramic emitters produce far infrared in roughly the 5 to 14 micrometre band. That is around ten times the wavelength of the near-infrared in a red light panel.

Where the energy lands

Between roughly 600 and 1100nm sits the optical window, a band where melanin, haemoglobin and water all absorb relatively weakly and light passes into tissue. Every therapeutic red light device lives inside it, which is why near-infrared can reach muscle and joint capsule. Wavelengths covers the depth question in detail.

Far infrared does not get that far. Tissue is around 70 percent water, and water absorbs strongly once you pass a micrometre. The ICNIRP statement puts it plainly: far infrared radiation is absorbed in the epidermis and dermis, with most energy absorbed in the surface layers.

So the marketing claim that infrared saunas heat you "from the inside out" has the physics backwards. The energy is absorbed at the skin, and the rest of the effect is your circulatory system moving that heat around, exactly as it would with any other heat source.

Two completely different mechanisms

Red light therapy is proposed to work photochemically. Red and near-infrared photons are absorbed by cytochrome c oxidase in the mitochondrial electron transport chain, and the effect follows from that absorption event rather than from any temperature change. A properly used panel barely warms you.

A sauna works thermally. The benefit, whatever its size, comes from raising core temperature and the cardiovascular and heat-shock responses that follow: heart rate rise, peripheral vasodilation, plasma volume shifts, sweating. The heat is not a side effect. The heat is the intervention.

That difference has a practical tell. If a red light session feels hot, the device is running warm rather than delivering more useful light. If a sauna session does not feel hot, it is not doing the thing saunas do.

The evidence for red light

Skin has randomised trials with instrument endpoints. Wunsch and Matuschka reported increased intradermal collagen density on ultrasound and reduced skin roughness on profilometry after 30 sessions, in Photomedicine and Laser Surgery in 2014.

Hair has sham-controlled trials with countable outcomes. Lanzafame and colleagues reported a 39 percent increase in hair counts over sham in Lasers in Surgery and Medicine in 2013.

Pain has a careful meta-analysis. Stausholm and colleagues pooled 22 randomised placebo-controlled trials in knee osteoarthritis in BMJ Open in 2019 and found meaningful pain reduction, but only in trials that used doses inside recommended ranges.

The full picture, including where it is weak, is in does red light therapy actually work.

The evidence for sauna, and its limits

The headline study is Laukkanen and colleagues in JAMA Internal Medicine in 2015. They followed 2,315 middle-aged Finnish men for a median of nearly 21 years. Compared with one session a week, men using the sauna two to three times a week had a 22 percent lower risk of sudden cardiac death, and those going four to seven times a week had a 63 percent lower risk.

That is a large association from a long follow-up, and it is worth taking seriously. Three caveats travel with it.

It is observational. People who sauna four times a week in Finland differ from people who go once, in ways adjustment cannot fully remove.

It was traditional Finnish sauna, at temperatures around 80 to 100 degrees Celsius. Infrared cabins typically run 45 to 60 degrees. The thermal load is not equivalent.

It was one cohort, in one country, in men.

For infrared specifically, the best overview is Hussain and Cohen's systematic review in Evidence-Based Complementary and Alternative Medicine in 2018, which covered 40 clinical studies and 3,855 participants across both Finnish and infrared saunas. Their assessment of the evidence base is the useful part: only 13 of the 40 studies were randomised controlled trials, only three of those were judged at low overall risk of bias, and over half of all studies involved 30 or fewer participants.

Their conclusion on the comparison is direct. There is not yet enough evidence to distinguish any particular health differences between repeated Finnish-style and repeated infrared sauna bathing.

The most developed infrared protocol is Waon therapy, developed in Japan, using a far infrared dry sauna at 60 degrees for 15 minutes followed by 30 minutes of blanket-wrapped rest, studied in chronic heart failure populations. That is a clinical protocol under supervision, not a wellness cabin, and it should not be used to support general claims.

The "full spectrum" problem

Some sauna manufacturers advertise near-infrared or red light alongside far infrared. Read the hardware, not the label.

Carbon and ceramic panels emit far infrared. They cannot produce 660nm or 850nm output. If a cabin genuinely delivers those wavelengths, it does so through separate LED modules, and those modules have their own irradiance, distance and coverage characteristics that almost nobody publishes.

A cabin with a small LED panel in one corner is not delivering the doses used in the photobiomodulation trials to your whole body. Why irradiance numbers are usually wrong applies here with extra force, because sauna brands publish even less measurement detail than panel brands do.

Which one, for what

If your goal is skin, hair, or a specific painful joint, the red light literature is where the trials are, and a device that touches or sits close to the target tissue is what those trials used.

If your goal is a general cardiovascular and relaxation stimulus, sauna has the longer epidemiological association, mostly from traditional saunas rather than infrared cabins.

They are not substitutes and there is no reason they cannot be used in the same week. There is also no published evidence that combining them produces anything beyond what each does separately, so treat any "synergy" claim as unsupported.

One practical note. If you use both, do the red light session separately rather than inside a hot cabin. Heat, sweat and steam sit between the emitter and your skin, and none of the trials were run in those conditions.

FAQ

Does an infrared sauna give me the benefits of red light therapy? No. The wavelengths are roughly ten times longer and are absorbed at the skin surface rather than passing into tissue. Unless the cabin contains genuine near-infrared or red LED emitters, it is delivering heat, not photobiomodulation.

Is a red light panel a cheaper sauna? No, and it should not make you sweat. If your panel is producing enough heat to raise core temperature, that is waste heat from the hardware rather than a therapeutic effect.

Which has better evidence overall? They are difficult to rank because they are measured against different outcomes. Red light has more sham-controlled trials with objective endpoints. Sauna has a much longer observational follow-up in a large cohort, with weaker controlled trial evidence behind it.

Can I use both on the same day? Nothing in the literature prohibits it. Do them as separate sessions rather than combining, and judge each on its own timeline. How long before results show covers what those timelines look like.

Sources

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