The Spectrums of Infrared

An overview of the properties of each band of infrared. Near, medium and far.

Infrared light is a type of electromagnetic radiation that lies just beyond the visible spectrum, between visible light and microwaves. It is typically divided into three main bands: Near-Infrared (NIR), Mid-Infrared (MIR), and Far-Infrared (FIR). Each band has unique properties, benefits, and drawbacks, making them useful for various applications in health, science, and industry. This chapter explores these bands in detail, highlighting their characteristics and uses.

Near-Infrared (NIR)

Wavelength Range: 0.7 to 1.4 micrometers

Penetration Depth: NIR waves penetrate the skin but do not reach as deeply as FIR. They primarily affect the epidermis and dermis layers, making them more suitable for superficial treatments.

Therapeutic Benefits:

  • Skin Health: NIR is commonly used for improving skin health, stimulating collagen production, and reducing wrinkles and fine lines.
  • Pain Relief: Provides pain relief for conditions such as arthritis and muscle soreness, though it is generally less effective for deep tissue issues compared to FIR.
  • Wound Healing: Promotes faster wound healing by stimulating cellular activity in the skin and upper tissue layers.
  • Circulation Improvement: Improves blood flow, although its effects are more limited to the surface compared to FIR.


  • Cosmetic treatments (anti-aging, skin rejuvenation)
  • Pain relief devices for superficial issues
  • Medical treatments for wound healing and skin conditions


  • Medical Applications: NIR is widely used in medical imaging techniques, such as Near-Infrared Spectroscopy (NIRS), which helps in monitoring brain activity and muscle oxygenation. Its deep tissue penetration is useful for assessing the oxygenation status of tissues and organs without invasive procedures (Fantini et al., 2018).
  • Photobiomodulation Therapy: NIR light is used in therapies to promote wound healing, reduce inflammation, and relieve pain. It stimulates cellular activity by enhancing mitochondrial function, leading to increased ATP production and improved cellular repair mechanisms (Hamblin, 2017).
  • Night Vision and Optical Devices: Due to its penetrative ability and low scatter in biological tissues, NIR is extensively used in night vision equipment and various optical devices.


  • Thermal Effects: High-intensity NIR can cause thermal damage to tissues if not properly regulated. Prolonged exposure to NIR light can lead to skin burns and eye damage.
  • Limited Surface Effects: While NIR penetrates deeply, it may not be as effective for surface-level treatments compared to other bands like FIR.

Mid-Infrared (MIR)

Wavelength Range: 1.4 to 3 micrometers


  • MIR wavelengths are intermediate.
  • This band is particularly absorbed by water and organic molecules, making it useful for various analytical and industrial applications.


  • Spectroscopy and Chemical Analysis: MIR is used extensively in Fourier-transform infrared (FTIR) spectroscopy for identifying chemical compositions. This technique is crucial in fields like biochemistry, pharmaceuticals, and environmental science (Smith, 2011).
  • Thermal Imaging: MIR cameras are used in thermal imaging to detect heat patterns, useful in industrial inspections, building diagnostics, and medical thermography.
  • Laser Surgery: MIR lasers, such as are used in precision surgical procedures because they are absorbed by water and biological tissues, allowing precise cutting with minimal damage to surrounding areas.


  • Cost: MIR technologies, including sensors and lasers, are often more expensive due to the complexity of their production and the materials required.

Far-Infrared (FIR)

Wavelength Range: 3 to 1000 micrometers

Penetration Depth: FIR waves penetrate deeper into the body, reaching muscles, tissues, and even bones. This deep penetration allows FIR to be more effective in treating deep-seated issues such as joint pain, muscle stiffness, and chronic conditions.

Therapeutic Benefits:

  • Enhanced Blood Circulation: FIR helps expand blood vessels, improving blood circulation and delivering more oxygen and nutrients to cells.
  • Cellular Regeneration: Supports cellular repair and regeneration, aiding in the healing of wounds and injuries.
  • Detoxification: Promotes sweating at a cellular level, helping eliminate toxins from the body.
  • Stress Reduction: Has a calming effect, reducing stress and anxiety, and promoting relaxation for better sleep quality.
  • Immune System Boost: Enhances the immune response, making the body more resistant to infections and diseases.
  • Reduction of Bacteria and Mold: Effective in reducing harmful bacteria and mold in food, extending shelf life and ensuring safer consumption.

Summary of Key Differences between near and far infrared.

  1. Penetration Depth: FIR penetrates deeper into the body than NIR, making it more effective for treating deep-seated issues.
  2. Therapeutic Scope: FIR is better suited for overall health and wellness, including detoxification, deep tissue pain relief, and boosting the immune system. NIR is more effective for skin-related treatments and superficial pain relief.
  3. Applications: FIR is widely used in therapeutic devices, saunas, pet care, and food preservation. NIR is commonly found in cosmetic treatments and medical devices for skin health and superficial wound healing.

Both FIR and NIR have their unique benefits and applications, making them valuable tools in different therapeutic contexts.

What is the difference between near and far infrared?

Near infrared is in the wavelength of 0.76 microns to 1.5 microns

Far infrared ranges from 4 to 1000 microns.

Near infrared has a shorter wavelength and is therefore more energetic.

Humans send off a frequency of 9.4 microns, and water sends off a frequency of 8 microns. 4-14 micron energy is pretty much the same as human energy. So they "Resonate".

Near infrared is not absorbed by water as well, human skin even has developed to reflect up to 35% of near infrared to protect itself. Near infrared is closer to the ultraviolet spectrum which causes sunburn than far infrared is.

Because it is close on the light spectrum to far infrared it has many similar benefits but it is harsher and therefore has some potential risks.

Relax Sauna's far infrared radiators

are designed to emit the healing far infrared frequencies of 4-14 microns

The creators of the Relax Sauna knew about the potential skin damaging effects of near infrared and therefore designed the generators to stay within a tight temperature range so that primarily far infrared would be generated, as explained in the following video(the part about the generator begins at 5 minutes in).

Benefits & Explanation of Relax Far Infrared Saunas

Journal of Investigative Dermatology

Symposium Proceedings, August 2009

Effects of Infrared Radiation and Heat on Human Skin Aging in vivo

Learn More

Many of the claims made about near infrared

are based on research done using near infrared diodes and lasers, not near infrared saunas.

A misleading practice that many near infrared sauna companies have been doing is quoting research about near infrared that was performed using near infrared diodes and lasers. These devices use a concentrated light and therefore can penetrate the skin deeper. Look at the article citations on near infrared sauna website. Many of the studies listed are for LED lights and lasers. This can be misleading when the results of these studies are associated with near infrared saunas. 

Cutaneous effects and therapeutic uses

of heat with emphasis on infrared radiation

The adverse effects and therapeutic benefits of heat, specifically infrared radiation, on skin have received little attention.

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Because it is absorbed by water

far infrared is much better at raising the body's temperature

for use in heat therapy, hyperthermia.

Many pathogens and diseases cannot survive when the body's temperature is raised.

This is the reason you get a fever when you are sick, the body is trying to kill the infection by raising the temperature.

Far infrared is absorbed better than near infrared and so this creates a larger heat transfer when in a far infrared sauna. Because of this, health professionals have found that far infrared saunas are the best tool for creating hyperthermia heat treatment in their patients.

A man tested which sauna would raise his core temperature faster. He used an Apple watch which tracked his body temperature and found that the Relax sauna was the most effective by far. He posted his review on Reddit here. This test backs up a research article which proves that far infrared heats up the body at a deeper level.

Research proves far infrared heats up tissue deeper and creates a higher blood flow than near infrared lamps

Researchers compared the effects of a 150 watt far infrared lamp which uses the same far infrared radiators as the Relax sauna but is 10 times less powerful compared to the 1400 watt sauna versus a 250 watt Phillips near infrared light bulb, the kind used in the near infrared saunas. Click here to view the study.