The most common type of light therapy is of course also the most common source of light - the sun. This sort of therapy has been around for millennia. The most obvious therapeutic effect comes from the UV spectrum contained in sunlight. UV rays are deadly to almost all microorganisms which might attack all superficial wounds. The infra-red portion of sunlight (heat) increases circulation and metabolic activity of the area which it hits. Visible light in general has many more effects which have only been uncovered since the 1980's. One of these effects is to boost the ATP production cycle of the mitochondria in cells. ATP is the fuel molecule of cells, without it the cells die.

In the past few decades different forms of light therapy have been developed. Most of them have focused on the isolation of specific parts or spectra of the electromagnetic spectrum. Here is a diagram of the electromagnetic spectrum:


Mostly the wavelengths between infra-red and ultraviolet radiation have been used for different forms of therapy, although radioactivity (such as gamma radiation) has also been used in, for example, treatments for cancer. We will not delve into this theme however as it is too broad to be discussed here.

Infra-red Radiation:

Also called heat lamps, these devices emit heat to elicit a variety of biological effects such as increased enzymatic rates, increased oxygen usage and dissociation, and generally increased metabolic and circulatory rate. This is usually done by means of an infra-red (or heat emitting) light bulb. An example of its application would be on a sore muscle. It could increase circulation and thus aid the body in washing out metabolic wastes which had accumulated in the muscle. There is a large range of types of infra-red radiation. Depending on the ailment or issue at hand, different strengths and wavelengths of infra-red radiation can be utilized.

The human body also emits infra-red radiation. Once scientists grasped this fact infra-red imaging was developed. It can pinpoint which areas of the body are warmer than what is normal. These imaging methods can be used to make early detections of cancer. Cancers have more blood vessels than is normal for any body tissue. This means that they have more blood in them at any one time than the surrounding tissues. The larger amount of blood also gives off more heat and can therefore be imaged on specific devices. Usually white or red spots on the image indicate the hottest areas and black or blue indicate the coolest.

Ultraviolet Radiation:

This form of therapy came after the heat lamps. It was considered a major breakthrough because by simply switching on a UV light bulb, a wound or sample of blood could be sterilized of any unwanted organisms or chemicals. Also stabilization of protein changes became possible with different wavelengths of UV light, allowing for longer storage of plasma in blood banks. Once again there are varying wavelengths of UV radiation. As the wavelengths are decreased the radiation gains more and more energy and becomes closer to an X-ray as oppose to UV radiation. UV lamps also found use in the food industry to sterilize foods before canning or packaging it. Because of the high amounts of energy in UV radiation, these therapies can become harmful if over-exposure occurs.

Light Amplification by Stimulated Emition of Radiation (L.A.S.E.R.):

Lasers are still considered by many medical professionals to be one of the hallmarks of modern medicine. They produce very precise and intense pulses of photons and deliver them to a target. On the electromagnetic spectrum wavelengths are measured in nanometers (one billionth of a meter). An individual laser contains photons of only one colour. That means that a laser operates at only a single frequency or wavelength. Below is a diagrammatic representation of the waves of photons emitted by a typical laser. The emission is coherent, which means that all of the waves are in phase with one another. One wave consists of a crest (high point) and a trough (low point). When two crests overlap, they add to form a wave twice the size of the initial waves. When two troughs meet they subtract and form a trough twice as deep as the initial trough. Because of this property (coherence), lasers can emit very strong pulses of light which can carry for a long distance. The way in which a laser generates this powerful burst of photons is by exciting a gas or a mixture of gases. When the gas atoms are excited by either a flash of light or by a high voltage their electrons jump and release photons (explained here ). The excitable material (gas in our case) is enclosed in a tube which is capped by two mirrors. One mirror is completely silvered and does not let any light out. The other mirror is only half silvered and allows only photons of a certain wavelength to pass, thereby creating a coherent emission of light. Dependant on which excitable material is used the colour of the laser will change, however a laser is only ever one colour.

The applications of lasers in modern medicine are vast and span from eye surgery such as removing cataracts or lens reshaping across scar and tattoo removal to cosmetic uses such as hair or varicose veins removal. In the first instance of eye surgery the intense heat which a laser produces burns the targeted part of the eye. In the instance of tattoo removal the laser breaks up the dye which makes up the tattoo into smaller pieces which are then in turn collected by our immune systems. In the instance of scar or stretch-mark removal, the laser loosens the tight collagen fibers which make up the scar tissue. Sometimes slight inflammation is also initiated. Together these two effects cause the body to restructure the area where the scar was. This usually results in a diminishing of the amount of scar tissue.

Incoherent Polarized Light:

This is a therapy system which was developed in the 1980's along-side research which was being done for various laser applications in medicine. A Hungarian research team came across the fact that polarising light has biostimulatory effects. This therapy system is explained in detail here. After its discovery a Swiss company, Zepter International, offered to develop a device using this technology, and thus the Bioptron was developed. It has been used widely across Europe in private homes, hospitals and operating theaters for the past 20 years.