Infrared vs Red Light Therapy: Red, Near-Infrared and Far-Infrared Explained
Red light and infrared are neighbours on the spectrum, and "infrared" covers three very different bands. Red light is visible, roughly 620 to 700 nm. Near-infrared, from about 780 to 1400 nm, is invisible, travels a few millimetres further into the body than red, and is used alongside red in light therapy devices. Far-infrared, from 3,000 nm upwards, is absorbed in the top tenth of a millimetre of skin and felt as heat; it is what saunas and heating pads produce. So "infrared light therapy" on a label can mean a light treatment or a heat treatment, and the wavelength tells you which. This article sets out the bands, how deep each one goes, what different products emit, what trials found when they compared red with near-infrared, and how to tell that an invisible channel is working.
Is infrared the same as red light therapy?
No, although the two overlap: red light therapy devices usually combine visible red with near-infrared, the band of infrared closest to red. Far-infrared products are heaters and work in a different way.
The American Academy of Dermatology describes red light therapy as a treatment that uses red or near-infrared light. AAD. In both cases the effect studied comes from the light being absorbed in cells, not from warming the tissue. What is red light therapy covers how that works.
What is the difference between red, near-infrared and far-infrared?
Wavelength, and with it how deep the light goes and what it does when it gets there.
| Band | Wavelength | Visible? | How far it gets into skin | What it does |
|---|---|---|---|---|
| Red | About 620 to 700 nm | Yes | 2 to 3 mm | Absorbed in the skin; used for skin trials |
| Near-infrared (IR-A) | 780 to 1,400 nm | No, or a faint glow | Several millimetres, the deepest of any band | Reaches tissue under the skin; used with red in light therapy |
| Mid-infrared (IR-B) | 1,400 to 3,000 nm | No | Less than 1 mm | Absorbed by water in the skin; heat |
| Far-infrared (IR-C) | 3,000 nm to 1 mm | No | About 0.1 mm or less | Absorbed at the surface; heat |
The band limits and depths for infrared are those of the International Commission on Non-Ionizing Radiation Protection. ICNIRP, ICNIRP statement. The eye's sensitivity fades between about 700 and 780 nm, which is why sources give slightly different figures for where red ends and near-infrared begins; our other articles round the start of near-infrared to 800 nm. Definitions of "far" also vary: some standards start it much further out, but in health products it means 3,000 nm and above, often written as 3 to 14 microns.
Does far-infrared go deeper than near-infrared?
No, it is the other way round. Far-infrared is absorbed in roughly the top tenth of a millimetre of skin, and near-infrared is the only infrared band that travels millimetres into tissue as light.
The reason is water. Skin is mostly water, and water absorbs little red and short near-infrared light, more from about 970 nm, and strongly from about 1,400 nm upwards. Between about 650 and 1,350 nm lies what researchers call the optical window, where light gets furthest into tissue. Near-infrared window. Many pages say far-infrared penetrates deepest. What goes deep with far-infrared is the warmth, which spreads inward from the skin by conduction and blood flow. The radiation itself stops at the surface.
What do "infrared" products emit?
It depends on the product. Some emit narrow bands of near-infrared light with little heat, and others are heaters.
| Product | How it makes infrared | What comes out |
|---|---|---|
| LED panels and masks | LEDs or laser diodes | Chosen narrow bands, typically 630 to 670 nm red and 810 to 850 nm near-infrared, sometimes around 1060 nm. Little heat |
| Infrared heat lamp | A hot filament behind red glass | A broad spread of near- and mid-infrared. Mostly a heater |
| Infrared sauna | Warm panels or rods; some use filtered lamps | Mostly far-infrared, which heats the body directly |
| Far-infrared heating pad or mat | An electric element warms stones or ceramic | Far-infrared, as any warm surface gives off |
Sources: ICNIRP, Mayo Clinic. The Mayo Clinic describes an infrared sauna as one that uses light to make heat. Your own body is a far-infrared source too: anything at skin temperature radiates at around 10 microns. To tell what a product is, look for the wavelength. A narrow figure such as 850 nm is light therapy territory; 3,000 nm or "3 to 14 microns" is heat. Red light therapy devices compared covers heat lamps and mats in more detail.
Red or near-infrared: which is better?
Neither across the board. In head-to-head trials, red did better for a problem at the skin surface, both worked for skin ageing and for muscle, and only near-infrared passed through thicker tissue.
| Study | Compared | Finding |
|---|---|---|
| Lee 2007, 76 people, sham-controlled, split face | 633 nm, 830 nm, both, or sham, twice a week for 4 weeks | All three light groups improved wrinkles and elasticity; near-infrared alone also worked on skin |
| Aziz-Jalali 2012, 28 people with acne, split face | 630 nm against 890 nm laser, 12 sessions | Spots fell from about 28 to about 6 on the red side; no significant change on the infrared side |
| de Almeida 2012, 10 men, placebo-controlled | 660 nm against 830 nm laser on the biceps before exercise | Both raised peak force by 12 to 14% over placebo, with no difference between them |
| Jagdeo 2012, laboratory study | 633 nm against 830 nm through tissue | Near-infrared passed measurably through soft tissue and bone; red transmission was negligible |
Sources: Lee, Aziz-Jalali, de Almeida, Jagdeo. These are small studies. Together they are the case for a device that has both, with channels you can set separately. 660 nm vs 850 nm covers the practical choice.
Can you see or feel near-infrared light?
Mostly not. An 850 nm LED typically shows a faint dull red glow, and longer wavelengths such as 940 and 1060 nm typically show nothing.
The eye does not stop dead at one wavelength; its sensitivity falls away steeply past 700 nm. A strong 850 nm source typically shows as a dim red dot. Physicists give two reasons: the eye keeps a little sensitivity past its nominal limit, and an LED's output has a short tail into the visible. University of Illinois. This is why a panel running only its near-infrared channels looks almost switched off while it is delivering most of its output. Brightness is no guide to dose.
A way to check. Point a phone camera at the device. Phone cameras often pick up near-infrared that the eye cannot, and the diodes appear as pale dots on the screen. Institute of Physics. Some cameras filter infrared out. As a tip, the front camera on many phones filters less than the rear one. Look at the phone, never into the device.
Does near-infrared light get hot?
A little: any light that is absorbed ends up as some warmth, and mild warmth at close range is normal. It is not how the therapy works.
Far-infrared feels hot quickly because all of it is absorbed at the surface, where the skin's warmth sensors are. Near-infrared spreads its energy through several millimetres of tissue, so the same power feels milder. If skin feels hot under an LED device, or stays red afterwards, move back, turn it down or stop.
Is the sun a source of near-infrared?
Yes. A little over half of the sun's energy at ground level arrives as infrared, most of it near-infrared.
Of roughly 1,000 watts per square metre of sunlight at sea level, about 527 are infrared, 445 visible and 32 ultraviolet. Infrared. Sunlight also brings the ultraviolet that damages skin, which red and near-infrared devices do not emit.
Are there safety differences?
Three. Near-infrared needs eye protection because you cannot see it, far-infrared heaters need care with time because of the heat, and visible red calls for care on darker skin.
- Eyes and near-infrared. Bright visible light makes you squint and look away. Invisible infrared gives no such signal, and safety guidelines note that the lack of a visible stimulus removes that protective response. ICNIRP. With a panel, wear the goggles every time; do you need goggles explains why.
- Skin and heat. Long, repeated warmth from heat pads, hot water bottles and heaters can cause a net-like discolouration called erythema ab igne. DermNet. This is a risk of heat sources used for hours, not something reported with timed LED sessions.
- Visible red and darker skin. The AAD notes that darker skin tones are more sensitive to visible light, and advises seeing a dermatologist first.
Which should you choose?
Match the band to what you want it for.
- Skin texture and fine lines: red, usually with near-infrared alongside, as in the skin trials.
- Muscles and joints: near-infrared, which is what most of those trials used. See red light therapy for knee pain.
- Warmth, relaxation and a sweat: a far-infrared sauna or pad. It is a heat treatment and does not deliver the light doses used in red and near-infrared trials.
- Not sure: a device with both red and near-infrared, on separate controls.
Which bands do Kivorla devices use?
Red and near-infrared, with blue as a separate option. Neither device produces far-infrared heat as its purpose.
The 4-Wavelength Red Light Therapy Mask runs 665 nm red with 850 and 1064 nm near-infrared in one mode; you will see the red and little or nothing of the other two. The 9-Spectrum Red Light Therapy Panel has three red channels (630, 660 and 670 nm) and four near-infrared channels (810, 830, 850 and 1060 nm), each dimmable from 1 to 100%, along with blue and amber. Most of its output at six inches is near-infrared, at least 1200 of at least 1567 W/m², which is why it looks dimmer than it is and why goggles come in the box. Its surface stays at or below 40°C.
Read the precautions before ordering, since returns are accepted within 30 days, less a 10% restocking fee if the device is unopened with its seals intact, or 20% if it is opened but undamaged and complete. Standard shipping to the US, UK and Germany is free.
Kivorla devices are general wellness devices, not medical devices. If you have a medical condition, speak to your doctor before using a light device.