Ultraviolet Radiation (UVR) in Physiotherapy


Did you know that sunlight contains different types of ultraviolet radiation that can affect our health and well-being? Ultraviolet radiation (UVR) is a form of energy that’s invisible to the human eye, with wavelengths between 10nm and 400nm. It sits between visible light and x-rays in the electromagnetic spectrum.

Now, here’s the cool part: some types of UVR can actually be beneficial for us! The therapeutic part of the ultraviolet spectrum can be divided into three categories: UVA, UVB, and UVC. UVA and UVB are biotic, where as UVC is abiotic.

  • UVA ⇒ 400-315 nm
  • UVB ⇒ 315-280 nm
  • UVC ⇒ below 280 nm

UVA rays have longer wavelengths (400-315 nm) and can penetrate deep into the skin, which can cause skin damage over time. However, UVA can also be used to treat certain skin conditions like psoriasis and eczema.

UVB rays have shorter wavelengths (315-280 nm) and are responsible for sunburns and skin damage. But don’t worry – in small doses, UVB can also stimulate the production of vitamin D, which is essential for strong bones and a healthy immune system.

UVC rays have the shortest wavelengths (below 280 nm) and are the most harmful to living organisms. Luckily, UVC is mostly blocked by the Earth’s ozone layer before it reaches us.

electromagnetic spectrum

Production of UVR

The Sun emits a broad spectrum of ultraviolet radiation, including UVA, UVB, UVC. Both UVA and UVB reach the earth from the sun. however, UVC is filtered out by the ozone layer. For therapeutic purposes, some form of generator is used to emits UVR.

Types of UVR Generators

Two types of UVR generators-

  • Mercury vapor lamp– can be of two types;
    • Air cooled medium pressure mercury vapor (Alpene sun lamp)
    • Water cooled mercury vapor lamp (kromayer lamp)
  • Fluorescent lamps

A) Mercury Vapor Lamp-

mercury-vapor lamp is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light. These are used for the production of ultraviolet rays for therapeutic purposes.

For explanation, you may click here – Mercury Vapor Lamp for Production of UV Rays

B) Fluorescent tubes

  • One of the major problems with the mercury lamp is that it produces a certain proportion of short ultra-violet rays.
  • Special fluorescent tubes have been designed that produce mostely long-wave ultraviolet rays, which is beneficial for treatment
  • These tubes are about 120 cm long and made of a special glass that allows long-wave ultraviolet to pass through.
  • Inside the tube, a special coating called phosphor absorbs and re-emits the short-wave ultraviolet as longer waves.
  • A low-pressure arc is set up inside the tube between its ends by a process of ionization similar to that described for the mercury vapor tube.
  • Depending upon which particular phosphor is used,  the output of the tube may be part UVB and part UVA (280-400) or UVA (360-400nm), as in the PUVA apparatus, but accurate control of the emitted wavelength is possible.

Theraktin tunnel

therktin tunnel

  • The theraktin tunnel is a semi-cylindrical frame in which are mounted four fluorescent tubes.
  • Each tube is mounted in its own reflector in such a way that an even irradiation of the patient is produced, allowing treatment of the whole body in two halves.
  • Normally fluorescent tubes with a spectrum of 280-400 nm are used.

PUVA apparatus

  • For the treatment of psoriasis, where a large amount of UVA, is required, the fluorescent tubes are used.
  • The tubes are usually mounted in a vertical battery on a wall, or four sides of a box surrounding the patient.
  • This form of ultra-violet is usually given two hours after the patient has taken a photoactive drug such as psoralen: hence the term PUVA (psoralen ultraviolet A)

Absorption of UV Rays in body

The superficial layer of our body is skin. it is a protective layer of our body. it absorbs the ultraviolet light and prevent its penetration down to unprotected or weak cells.

The extent of the reaction or damage depends on the wavelength of ultraviolet and the amount of ultraviolet absorbed.

adsorption of UV rays in skin

UVC is absorbed in the epidermis along with UVB, and UVA may penetrate as far as the capillary loops in the dermis.

Physiological Effects of UVR

Immediate/ acute effects

  1. Erythema
  2. Pigmentation
  3. Increased skin growth
  4. Vitamin D production
  5. Prophylactic effect
  6. Immunosuppressive effects
  7. Effects on eye

Long term/ chronic effects

  1. Solar elastosis or aging
  2. Cancer

A) Immediate acute effects-

1) Erythema:

Erythema is reddening of the skin as a result of an inflammatory reaction stimulated by ultraviolet rays ⇒ release of histamine like substance ⇒ dilation of the capillaries and arterioles and exudation of fluid into skin.

The Erythema reaction has been used to classify doses of ultra-violet given to patients. there are 4 degrees of erythema E1, E2, E3, and E4.

Degree of Erythema Latent Period (hours) Appearance Approximate duration Skin edema Skin discomfort Desquamation Relation to E1
E1 6-12 h Mildy pink <24 h None None None x 1
E2 6 h Definite pink red, blanches on pressure. 2 days None Slight soreness Powdery x 2.5
E3 3 h Very red, does not blanch 3-5 days Some Hot and painful Thin sheets x 5
E4 <2 h Angry red 1 week Blister Very painful Thick sheets x 10
Table- Standard doses of ultra-violet (E1- E2) classified by erythema reaction

2)  Pigmentation:

  • Pigmentation or tanning of the skin follows the erythema.
  • Its amount varies with the intensity of the erythema.
  • It is due to the increased deposition of the pigment melanin formed in the basal cell layer of the skin by the melanoblasts and migrates to the superficial layers of the epidermis.

3) Desquamation (increased skin growth):

  • Desquamation or peeling is proportional to the intensity of the erythema.

4) Vitamin D production:

  • UVB is able to convert sterols in the skin, such as 7-dehydro-cholesterol  to vitamin D.
  • Vitamin D is required to assist in the absorption of calcium and phosphorous from the intestine to blood stream.
  • Suberythemal dosage of UVB are adequate  to promote vitamin D synthesis.

5) The Prophylactic effects:

The resistance of the body to infection is increased as a result of the stimulation of reticuloendothelial system ⇒ antibodies against bacteria and toxins.

6) Immunosuppressive effects:

  • UV destroys Langerhan’s cell and stimulates the proliferation of suppressor T cells, ( T cells are regulatory in that they inhibit antibody  production)
  • This immunosuppressive effects may contribute to the development of skin cancer.
  • In short, UV  radiation induces a state of relative immunosuppression that prevents tumor rejection.

7) Effect on eye:

  • Strong doses of UVB and C radiation to the eyes can lead to conjunctivitis and photokeratitis results in
    • Irritation of the eye,
    • A feeling of grit in the eye,
    • Watering of the eye and
    • Aversion to light (photophobia).
  • In severe cases intense pain and spasm of the eyelid may be present this is also known as a ‘Snow Blindness’.
  • While UVB and C are absorbed  in the cornea,UVA can pass through to be absorbed mainly in the lens of the eye.
  • The strong doses of UVA may lead to the formation of Cataracts.

B) Long term/chronic effects-

1)Solar elastosis and ageing-

  • Prolonged exposure of UVR lead to, premature ageing of the skin, this is especially so in the fair-skinned.
  • Decrease function of sebaceous and sweat glands.
  • Loss of elastic tissue
  • The skin becomes wrinkled, dry and leathery.

2) Cancer-

  • Skin cancers, basal cell, and squamous cell carcinomas.
  • Carcinogenesis is a danger, as these rays may have an effect on DNA and thus on cell replication.
  • Shorter ultraviolet waves should be avoided and courses of treatment should not exceed four weeks.

UVR Dosages

Skin response to UVR depends upon:

  1. Quantity of UVR energy applied to the skin
  2. Biological responsiveness of skin.

1) Quantity of UVR energy applied to the skin, which depends upon-

  • Output of the lamp.
  • Distance between the lamp and the skin
  • Angle at which radiation falls on the skin
  • Time for which radiation is applied on the skin.

2) Biological responsiveness of skin-

Biological responsiveness of skin of UVR

The following skin types are described,  from the most reactive through to the least:

Calculation of dosage

  • E1 is determined from the skin test and the other erythemal dosages can be calculated as follows-
    • Suberthermal  75% of E1
    • E2 = 2.5×E1
    • E3 = 5×E1
    • E4 = 10×E1
    • Double E4 = 20×E1
  • E4 and double E4 are used on an open wound
  • Minimal erythema dose (MED)– The smallest dose of UVR to result in erythema that is just detectable by eye at between 8-24 hours after exposure is called minimal erythemal dose.

Progression of UV dosage

Dosage can be progressed as follows:

  • Suberythermal – previous dose plus 12.5%
  • E1- previous dose plus 25%
  • E2- previous dose plus 50%
  • E3- previous dose plus 75%

Dosage used on open wounds are not progressed because there is no epidermis to thickness.

Alteration of the intensity with distance

To irradiate a smaller area the source is moved nearer to the patient but the time of exposure must be altered to maintain the same intensity under the law of inverse squares.


Therapeutic Effects and Uses of UVR

The therapeutic effects produced and the uses are listed as under:

A) Psoriasis

  • Psoriasis  is a chronic skin disease of unknown causes,
  • which are manifested either as silvery scales covering the pink or red plaques (chronic discoid psoriasis),  or the small lesions scattered on the trunk, postural psoriasis, generalized postural and erythrodermic psoriasis, flexural psoriasis.
  • In about 7-42percent of patients with psoriasis, there might occur arthritis, called psoriatic arthritis.
  • The aim of ultraviolet irradiation is to decrease the rate of DNA synthesis in the cells of the skin and thus slow down their proliferation.
  • It must be realized that, the long ultraviolet rays like  UVB, UVA are beneficial for the treatment of psoriasis but no UVC.
  • The different treatment regimens include:
    • The Goeckerman regimen:  This consists of the application of coal tar 2-3 times a day with general UVB radiation given once a day, as a suberythemal or E1(MED) dose.
    • Leeds or Ingram regimen:
    • PUVA (Psoralen ultra-violet A):

B) Acne vulgaris

Ultraviolet radiation is given in E2 doses for acne vulgaris, with the following aim-

  1. An erythema will bring more blood to the skin and so improve the condition of the skin
  2. Desquamation will remove comedones and allow free drainage of sebum, thus reducing the number of lesions.
  3. The UVR will have a sterilizing effect on the skin.

C) Eczema

  • This patients are benefited by mild doses of UVR.

D) Chronic infection

  • Ultraviolet radiation at high doses are helpful for the treatment of chronic infection.
  • An E4 dose can use for it.

E) Vitiligo

  • One evidence suggests that topical glucocorticoids and psoralen-UVA (PUVA) or narrowband UVB at a wavelength of  311nm are effective for the management of this condition.

F) Treatment of vitamin deficiency

  • As already stated, cholecalciferol (vitamin D3) is formed in the skin, by the action of UVB and UVC on 7-dehydrocholesterol.
  • Exposure to artificial UVR or artificial sun light is curative for  vitamin D deficiencies such as rickets, osteomalacia, and senile osteoporosis.

G) Protection for hypersensitive skin

Person who work outside in the strong sunshine region, can have reduce effects of sun burn .

H) Hypertension

Suberythemal doses of UVB reducing blood pressure.

I) Pruritus

Pruritus due to uremia in patient with chronic renal failure also shows result when treated using suberythemal doses of UVB

Contraindications of UVR

  • Irradiation of the eyes
  • Skin cancer
  • Pulmonary tuberculosis
  • Cardiac, kidney and liver disease
  • Systemic lupus erythematosus
  • Fever

Precautions to the Use of UVR

  • With patients taking photosensitizing medication
  • Photosensitivity
  • Recent Radiotherapy
  • Until the effects of the prior dose have disappeared

Dangers of UVR

  • Burn
  • Premature skin aging
  • Carcinogenesis
  • Damage to eyes
  • Adverse effects due to PUVA


  • Electrotherapy Therapy Simplified – Basant Kumar Nanda