Infrared radiation therapy involves using electromagnetic waves between visible light and microwaves to heat superficial tissues. It can be generated by luminous sources like tungsten filament lamps or non-luminous sources like heated coils. Infrared radiation increases blood flow, relieves pain and muscle spasms, and accelerates healing through superficial tissue heating. Proper application and monitoring are needed to provide benefits while avoiding potential risks like burns.

1. Infrared Radiation (IR/IRR)
By : Dr. Vicky Kasundra
1st Year MPT (Neurological Science)

2. Introduction
• Infrared rays are electromagnetic waves.
• It lies between visible light and microwaves.
• Wavelength : 750 nm to 400000 nm.
• Frequency : 4 * 1014Hz and 7.5 * 1011Hz.
• Infrared radiation (IR/IRR) therapy is a superficial heating
modality.
• It works on radiation principle of heat transfer.

4. Classification
• Based on wavelength
IRA
IRB
IRC
760-1400 nm
1400-3000 nm
3000 nm-1 mm (not
used in therapy)

5. • Former classification
Near or short IR – 760-1500 nm
Far or long IR – 1500-15000 nm

6. Sources of infrared radiation
• The sources of infrared can be either natural or artificial.
• Artificial infrared is generally produced by passing electric
current through coiled resistance wire.
• Sun is the natural source of infrared radiation.
• In the physiotherapy department Infrared radiation are
produced by two type if generators:
1. non-luminous generators
2. luminous generators

7. Production of Infrared
• Any heated material will produce infrared (sun, electric
bulb, coal fire, gas fire etc), the wavelength being
determined by the temperature.
heat provide to any
material
Molecular vibrations of
atoms
Collision of molecules
Production of heat or IR

8. • Higher temperature are associated with higher frequency
and shorter wavelength radiation.
• The most convenient method is to heat a resistance wire by
passing an electric current through it.

9. Non-luminous generators
• Non-luminous generator consists of a simple type of
element or coil wound on a cylinder of some insulating
material such as fireclay or porcelain.
An electric current is passed through the wire which results in the
production of heat.
This heat produces infrared rays which are transmitted through the
porcelain.
Porcelain gets heated by the method of conduction but the radiations
generates in this way also include some of the visible rays.

10. • To avoid this, the coil is embedded in fireclay or porcelain or placed
behind fireclay.
• Now the emission of rays is entirely from the fireclay which is
commonly painted black and thus very few visible rays are produced.
• The element or the coil is thus placed at the focal point of a parabolic
or spherical reflector.
• Wire –mesh screens are placed in front of reflector to prevent
accidental contact with the hot emitter.
• The reflector is mounted on a stand and its position can be adjusted as
required.

13. Disadvantage :
• All of these non-luminous generators take some time to get
heated up for the production of infrared radiations, so they
should be switched on before 5-15 minutes of the treatment.
Advantage :
• Non-luminous generators provide infrared rays only.

14. Luminous Generators
• Luminous generators emit infrared, visible and a few
ultraviolet rays.
• Heat produce by it is called radiant heat.
• These generators are in the form of incandescent lamps or
bulbs.
• An incandescent lamp consists of a wire filament enclosed
in a glass bulb, which may contain an inert gas at low
pressure.

15. • The filament is a coil of fine wire which is usually made up
of tungsten.
• Tungsten is a metal which is used because it can tolerate
repeated heating and cooling.
• Front of bulb is usually red to filter out shorter visible &
ultraviolet rays.
• Incandescent bulb is usually mounted at the center of the
parabolic reflector and the reflector is mounted on an
adjustable stand.

17. Disadvantage :
• luminous generators emit infrared rays, visible as well as
ultraviolet rays.
Advantage :
• Require less time for production of IRR.

19. Depth of penetration of rays
Luminous generator
• Produces infrared rays
having wavelength
between 750-1500 nm
(maximum 1000 nm).
• It can penetrate into
epidermis, dermis and
subcutaneous tissue (5-
10 mm)
Non-luminous generator
• Produces infrared rays
having wavelength
between 1500-12000 nm
(maximum 4000 nm).
• It can penetrate into
epidermis & superficial
dermis (2 mm)

20. Choice of luminous and non-luminous
source
• In most cases luminous and non-luminous generators are
equally suitable, but in some instances one proves more
satisfactory than the others.
• Luminous radiation : more efficient tissue heating source
since it penetrates further (because peak emission is in the
short infrared) and therefore the energy is distributed in a
larger volume of tissue.
• Non-luminous radiation : with peak emission around
4000nm, is absorbed almost entirely in the skin.

21. • If the desired effects are due to:
Heating : the luminous infrared is preferred
Sensory stimulation : the non-luminous is preferred
• When there is acute inflammation or recent injury, the nom-
luminous generator were used.
• When there is chronic lesion or injury, the luminous
generator were used.

22. Luminous Non-luminous
Sources & types Tungsten filament enclosed in bulb
with insert gas at low pressure
Electric coil wire wrapped
around fireclay or porcelain
Wavelength 750-1500 nm (maximum 1000 nm) 1500-12000 nm (maximum
4000 nm)
Emission 70% near IRR, 24% far IRR, 5%
visible light,
1%UV
90% far IRR, and 10%
near IRR
Penetration Epidermis, dermis &
subcutaneous tissue (5-10mm)
Epidermis & dermis
(2mm)
absorption Deep Superficial
Physiological
effect
Pain reduction via counter
irritant effect
Pain reduction via
sedative effect
Uses Chronic conditions Acute conditions
Distance 40-60 cm from treated area 65-80 cm from treated
area
Treatment time 15-20 minutes 20-30 minutes

23. Power
The power of IR sources can described as;
• Small lamps (luminous and non-luminous), usually
250-500W.
• Large, non-luminous, 750-1000W.
• Large, luminous, 650-1500W.

24. Emission
Non-luminous
• Mainly 3000-4000 nm (long IR), with about 10% between
1500 nm and visible (short IR)
Luminous
• Approximately 70% short IR
• 5% visible
• 24% long IR
• 1% UVR absorbed by glass of bulb

25. Absorption and penetration of infrared
radiation
• All radiations, when it strikes the body, will be reflected,
some will penetrate, to be scattered, refracted and ultimately
absorbed in the tissues.
• Close to 95%of the radiation applied perpendicular to the
skin is transmitted rather than reflected.
• The transmitted energy is rapidly absorbed so only small
amounts of radiation penetrate to the subcutaneous tissues;
most is absorbed in the skin.

26. • The absorption of infrared and the maximal penetration of
the rays will depend upon the following variables:
1. frequency or wavelength of the rays
2. thermal conductivity of the tissue
3. angle of incidence of the rays
4. density of each tissue
5. distance from the source of infrared
6. patency of the circulation
7. source of the infrared

28. Penetration
• Penetration is depends on penetration depth.
• Penetration depth : The depth at which 63% of the
original radiation has been absorbed and 37% remains.
• Very long wavelength infrared ( around 40000nm ) behaves
like microwave and penetrates several centimetres.
• However, the long infrared used therapeutically is absorbed
at the surface, much of it by the water on the skin surface.

29. • At around 3000nm, the penetration depth is about 0.1 mm.
• There is increasing penetration with decreasing wavelength
in the short infrared region, to a maximum penetration
depth of about 3mm around the 1000nm wavelength region.
• Very short infrared and red visible radiation have
penetration depths of about 1 or 2 mm, while those of the
rest of the visible spectrum penetrate much less.
• In fact, at the blue end of the visible spectrum, the
penetration depth is about 0.07 mm and decreases uniformly
with wavelength through the UVR region.

31. Physiological effect
Cutaneous vasodilatation
• Due to the heating of the cutaneous structure, infrared
radiations produce local cutaneous vasodilataion.
• This effect is due to;
1. The liberation of chemicals such as histamine and similar
substance.
2. Due to the direct effect on blood vessels.
• The vasodilatation starts after 1-2 min and is largely due to
arteriolar vasodilatation.

32. • Due to heating erythema start developing.
• The rate of erythema depends on rate and degree of heating.
• For normal individuals, heating the skin to about core
temperature (37 c) over some 20 minutes will lead to very
mild erythema; heating to around (42 c) will lead to marked
erythema.
• The local erythema lasts for about 30 minutes after radiation
has stopped.

33. Sweating
• The heat produced by the IRR increases the activity of the
sweat glands, causing release of sweat.
• Produced sweat absorb some of the applied infrared
radiation and leads to surface cooling as it evaporates.
Sensation
• Due to the effects of heating the thermal heat receptors in
the skin are stimulated, giving the sensation of warmth.

34. Increase in metabolism
• As per vant hoff’s law, which states that the chemical
changes are accelerated due to heat, the heat produced by
IRR increases the metabolisum, due to which there is
increased demand in the tissue for oxygen and food stuffs
which is maintained by an increased arterial flow.
• The waste metabolites produced are removed by increased
lymphatic and venous returns.

35. Chronic changes
• Excessive and prolonged IR application can cause the
destruction of erythrocytes, releasing pigments and causing
brown discoloration of the skin.
• This rarely occurs as a normal treatment.
• Epidemiological studies also indicate that due to prolonged
use of high temperature IR can produce carcinogenic effect.

36. Therapeutic uses
Pain relief
• Mild heating on the superficial tissues by IRR causes
sedative effects of superficial sensory nerve endings.
• Pain may be due to accumulation of waste products of
metabolism, an increased flow of blood through the part
removes these substances and thus relives the pain.

37. • The pain due to acute inflammation or recent injury is
relieved most effectively by mild heating.
• When pain is due to chronic injury, stronger heating is
required. The treatment may last up to 30 minutes.

38. Reduction of muscle spasm/muscle relaxation
• Mild heating by IR causes relaxation of muscles and thus
relieves spasm.
• Relief of pain also induces relaxation in muscles and helps
relieving muscle spasm associated with injury.
• Relaxation of muscles provide greater ROM to the
exercising part as it relieves muscular spasm.

39. Acceleration of healing and repair
• It accelerate healing and repair by increasing blood supply.
• IRR increase the temperature in the superficial tissues,
causing vasodilatation in the superficial tissues.
• It provide more WBC and fresh nutrients to the area being
treated.

40. • It also accelerates removal of waste products and helps
bring about resolution of inflammation.
• Fresh supply of blood rejuvenates the tissues, removes
waste products of metabolism and also relives muscle
spasms.
• Ex, Arthritic condition

41. Reduction of joint stiffness
• There is increased blood flow and consequent muscle
relaxation which leads to decrease in the joint stiffness and
improves range of motion.
Relives skin lesions
• In case of skin infections such as dermatitis, viral infections
caused due to bacteria.
• IRR can be given to destroy the bacteria and thus help to
reduce the infections.

42. Indications
• Subacute or chronic inflammatory conditions such as; Low
back pain, cervical spondylosis, osteo-arthritis, rheumatoid
arthritis.
• Skin infections
• Pressure sore/decubitus ulcer
• Bell’s palsy following middle ear infection
• Peripheral nerve injuries before the application of electrical
stimulation
• Prior to stretching, massage, mobilization, traction and
electrical stimulation

43. Contraindication
• Acute skin disease (dermatitis or eczema)
• Defective cutaneous circulation (Peripheral vascular
disease)
• Haemorrhagic condition
• Areas with impaired thermal sensation
• Recently radiated tissues (following radiotherapy)
• Over areas of scars
• Severe edema
• Region of suspected mallignant tumor
• Metal impalnts tissues
• Directly over Eyes
• After deep X ray or cobalt therapy

44. Advantages
• Cost effective
• Easy to use at home
• Dry heat is very comfortable in the winter
• Can be used to treat large areas, with local superficial
heating effects.
• Superficial tissue temperature can be increased; even
though the unit does not touch the patient.

45. Disadvantages
• Uneven body parts can not be treated due to uneven heating.
• Constant temperature source increases the risk of burns.
• Lack of therapeutic evidence.
• Heating only superficial tissues, not effective as moist heat
pack and paraffin wax.

46. precautions
• IRR exposure of the tissue should not be more than 30
minutes.
• Distance between the source of the lamp and the tissue
should not be less than 18 inches.
• Ask the patient not to touch the IRR lamp and wires during
the treatment.
• Ask the patient not to sleep and move towards IRR lamp
during IR radiation exposure.
• People with sensitive skin.
• Never apply IRR directly over the eyes and genitals.

47. Technique of application
Patient
• Position the patient in a suitable, well supported position
with the area to be treated exposed.
• Explain the nature and effects of the treatment to the
patient.
• Before starting the treatment examine the skin to be treated
and test the thermal sensation.

48. Apparatus
• If non-luminous lamp is chosen, switch it on at least 10
minutes prior to treatment, to allow time for it to warm and
reach its maximum emission.
• A luminous lamp needs no warm up time and can be
switched on once patient is ready for the treatment.

49. Setting up
• Expose the skin to be treated and cover the eye with towel
or goggles.
• Position the lamp 90 degree so that the radiation strikes the
surface at near right angle to achieve maximum penetration.
• Set the lamp at appropriate distance: about 60-75 cm for
large lamps and about 45-50 cm for the smaller ones.

50. Instructions and warnings
• Ask the patient to indicate the level of heat they can feel
and where.
• Advice the patient not to touch any part of lamp or not to
move during treatment and alert therapist if it is more than
comfortably warm level of heating.

51. Application
• The intensity of the heating is most IR lamps is controlled by the
distance of the lamp from the skin.
• Adjacent areas can be protected from heating by placing the
layer of towel.
• The therapist should check the level of heating on completion of
the set up and again after 5 to 8 minutes and, if required, adjust
the distance of the lamp to the skin.
• IR is usually only applied for 10 to 15 minutes as it is only part
of a treatment, not a treatment itself.

53. Termination
• On completion of the treatment the skin should be carefully
checked.
• On palpation it may feel mildly or moderately warm and a
moderate erythema should be evident.

54. Dangers
Burn
• Excessive heating of superficial tissues can causes burn.
• Erythema after the treatment is a physiological effect, but if the
intensity of IR is more, it may cause the formation of blisters.
• The burn may be caused due to the following reasons:
1. If intensity of radiation is too high
2. If sensation is not proper
3. Patients fails to report over heating
4. Unconscious patient
5. Patient moves closer to the lamp
6. Falls asleep during the treatment
7. Metal implanted tissue

55. Electric shock
• It can occur if some exposed part of the circuit is touched
by the patient.
• Due to heating of the wires in the circuit, insulation of wires
may go off and thus regular checking of wires is necessary
to avoid electric shock.

56. Faintness of giddiness
• Excessive IRR cause fall in BP which may result in
faintness or giddiness due to hypoxia of the brain.
• This is observed when the patient rises up suddenly from
the recumbent position after extensive treatment.

57. Reduced or altered peripheral blood flow
• Do not use IRR if the vascular response is insufficient
because of the risk of tissue damage.
• Areas affected by arterial disease, such as atherosclerosis,
arterial injury or after skin grafting, should not normally
treated with IRR.

58. Headache
• IRR over the back of the head may cause headache.
• Headache is also occur when treatment is given during hot
weather.
Following Radiotherapy
• Avoid IRR at least 2 months following radiotherapy.

59. Injury to eyes
• Direct heating over the eyes causes drying up and thus leads
to corneal and retinal burns.
• Another problem is forming cataracts.
Infection/skin inflammatory conditions
• Avoid applying heat over acute skin infections or previously
known tumours to prevent spreading of disease.