Infrared in Medical Applications

Background

Infrared was discovered by the astronomer William Herschel during an experiment in which he found radiation beyond the visible solar spectrum. This radiation is invisible to the human eye but has physical properties similar to visible light and exhibits noticeable thermal radiation. Because it lies beyond the red end of the visible spectrum, it was named infrared. Its wavelength range is wide, approximately 0.75-1000 micrometers. Shorter wavelengths in this range are called near infrared, and the longest wavelengths are called far infrared. Definitions vary by application; in practical use, wavelengths above 2.5 micrometers are often classified as far infrared.

Herschel's Experiment

In 1800, Herschel passed sunlight through a prism to produce a spectrum and used three alcohol thermometers with blackened bulbs to absorb radiant heat. He placed one thermometer in a visible color band and two outside the visible spectrum as background references. He observed temperatures increasing in sequence from violet, blue, green, yellow, and orange to red.

More surprisingly, he found that a region just beyond the red visible band, where no light could be seen, registered an even higher temperature. This was the first detection of invisible radiation, later called infrared.

It should be noted that the Sun's emission peaks near a wavelength of 5800 A (green light). Herschel measured increasing temperature at longer wavelengths because dispersion in his experiment caused energy at longer wavelengths to be more concentrated, while shorter-wavelength energy was more dispersed.

Proposed Biological Effects

1. Genetic level: It is claimed that infrared can help maintain health at the genetic level. For example, wild animals often recover by sun exposure, while prolonged dark environments can lead to health deterioration.
2. Cellular effects: Far infrared and certain frequencies of the human body are said to be partially synchronous, producing resonance. This resonance is described as promoting ordered cell arrangement, reducing bound water molecule size, and aiding elimination of cellular toxins, which theoretically improves nutrient absorption and cellular health.
3. Vascular effects: Resonance can generate heat, causing vasodilation and enhanced blood circulation. Improved microcirculation is associated with better tissue perfusion; many circulation-related conditions such as hypertension, hyperlipidemia, and diabetes are claimed to improve when microcirculation is restored.
4. Nervous system effects: The nervous system includes central and autonomic components. Continuous vibrational stimulation is claimed to improve neural conduction and help regulate motor function and endocrine activity.
5. Fibers and textiles: Far infrared-emitting fibers can emit radiation in the 8-15 micrometer range, sometimes called the "life light." Their main medical effect is thermal. Wearing garments made from such fibers is claimed to relieve pain, activate cellular tissue, promote blood flow and microcirculation, enhance metabolism, strengthen immunity, and provide additional effects such as odor control, drying, dehumidification, and antibacterial action.

Mechanism and Metabolic Effects

Infrared is the component of sunlight that penetrates skin and subcutaneous tissue most effectively. Because certain far infrared frequencies are close to vibrational frequencies of cellular molecules, these waves can induce resonance of atoms and molecules within cells. Resonance and absorption produce frictional heating at the molecular level, raising deep tissue temperature, dilating microvessels, and accelerating blood flow. This process may aid in clearing vascular deposits and harmful substances, remove obstacles to metabolism, revitalize tissues, and promote enzyme production. The proposed outcomes include tissue activation, prevention of aging, and immune system strengthening. For this reason, far infrared is used to address disorders related to impaired blood circulation and microcirculation.

Additionally, some harmful substances in the body—such as heavy metals and other toxins from food, lactic acid, free fatty acids, fat deposits, sodium ions, uric acid, and residual cosmetic materials trapped in pores—are claimed to be excreted via metabolism and sweat through the skin, reducing renal burden.

Safety Considerations

Infrared emitted by combustion or electric heaters is often near infrared. Because near infrared has shorter wavelengths, it produces strong thermal effects and can cause burns to skin and eye lenses with prolonged exposure. Even shorter electromagnetic waves, such as ultraviolet, X-rays, and gamma rays, can ionize atoms and are more harmful. Far infrared has longer wavelengths and relatively lower photon energy, so it is associated with a lower risk of thermal injury.

Far infrared differs from low-frequency electromagnetic fields emitted by household appliances. Low-frequency fields can penetrate walls and alter characteristics of electric current, raising health concerns in some contexts. Far infrared penetration into skin is limited, typically about 0.01-0.1 cm, and the human body itself emits far infrared near 9 micrometers, so far infrared should not be conflated with low-frequency electromagnetic fields.

Clinical and Supportive Use

Far infrared has been applied as an adjunctive therapy for a range of conditions where promoting blood circulation is beneficial, including musculoskeletal soreness, tendonitis, pressure ulcers, burns, and wounds that are slow to heal.