Infrared rays are electromagnetic waves with wavelength of 750 – 4 lac nanometer. Any hot body emits infrared rays. For example the sun, gas fire, coal fire, electric fire, hot water pipes etc. The infrared rays are produced by two types of generators.

Non luminous generator provides infrared rays only while luminous generator emits visible and a few ultraviolet rays as luminous generator is often called radiant heat. The term infrared is generally being applied to the radiations from non luminous source.

Infrared radiation is an effective mean of relieving pain, when heating is mild the relief of pain is due to sedative effect on superficial nerve endings. Stronger heating of infrared stimulate the superficial nerve endings. It has been also noticed that pain is due to accumulation of waste product and because of stronger heating the blood flow increases which remove that waste product and the pain is relieved. In some cases the relief of pain is probably associated with muscle relaxation.

                                               

In acute inflammation, pain is reduced with mild heating because in recent injury tissue fluid accumulates in that area, the use of stronger heating will increase these processes which cause pain.

In chronic type of inflammation pain is reduced due to stronger heating. The infrared causes comfortable warmth and the treatment time should be round about 30 min.

Muscle relaxes most readily when the tissue is warm. The relief of pain also facilitates muscle relaxation. Infrared radiation is most helpful to achieve muscle relaxation and for the relief of muscle spasm associated with acute injury or inflammation.

The effect of infrared is mainly in the superficial tissues and this may be used in the treatment of superficial wounds and infections. Because a good supply of blood is essential for healing to take place and if there is infection, the increased number of WBCs and the increased exudation of fluid assist in the destroying of bacteria. When superficial joints are affected for example small joints of hand and feet (arthritis), the infrared radiation is more helpful in the vasodilatation of blood vessels. This vasodilatation can increase the blood flow (increased supply of oxygen and removal of waste product and food stuffs are available to bring about the resolution of inflammation).

The intensity of radiation should be low at the beginning but after 5 – 10 min when the vasodilatation occur (when the increased blood flow establishes). The strength of radiation may increase; this can be achieved by moving the lamp nearer to the patient. The physiotherapist should be at the hand throughout the treatment session and should reduce the intensity of radiations when the heating become excessive. Sweating is encouraged if the patient is provided with water drink.

Infrared radiations can cause superficial heat burn. Red patches are seen on the skin which subsequently blisters during or after the treatment. The burn is most often caused by 2 grade intensity of radiation. This process can occur when the patient does not understand the nature of treatment or fails to report the overheating or move neat the lamp or falls asleep. The physiotherapist must be at hand during the whole treatment session.

It can occur as a result of touching some exposed part of the circuit but the main danger arises if the live wire comes in contact with the apparatus casing.

Gangrene may be occurred when infrared is applied to the area of defective arterial supply.

Headache may occur if the sweating does not take place properly or if the treatment is given in hot weather.

Extensive irradiation may cause fall in BP which may result in faintness or giddiness due to hypoxia of the brain.

It has been suggested that exposure to IRR can cause cataract.

a)      Defective arterial supply

b)      Defective skin sensation

c)      Areas where there is danger of hemorrhage