How can ultraviolet light cause rickets

The UV light therapy (light therapy with ultraviolet light) is not only used in the treatment of dermatological diseases (see: UVB 311 nm light therapy; light therapy for psoriasis). In this article the effect of UV radiation on the vitamin D3 balance is discussed and the resulting therapeutic use is discussed.

Indications (areas of application)

  • Rickets - This disease occurs in childhood and is due to an insufficient supply of calcium or phosphate; this is usually caused by a vitamin D deficiency. For this reason, the mineralization of the growing bones is disturbed and skeletal changes occur.
  • Osteomalacia - This disease occurs in adulthood and corresponds to rickets.
  • generalized tendoperiostoses - spindle-like widening of the periosteum (periosteum) in the area of ​​the tendon attachments
  • Vitamin D Deficiency Diseases

The procedure

UV light is the invisible, higher-energy radiation that joins the violet of visible, natural light in the light spectrum.

The spectrum of UV radiation is divided as follows:

  • UV-A radiation (UVA1 - 320-340 nm; UVA2 - 340-400 nm) - so-called tanning radiation
  • UV-B radiation (280-320 nm) - This UV radiation stimulates the melanocytes (cells that produce the brown skin pigment), creates an inflammatory erythema (reddening) and is significantly involved in the synthesis or activation of vitamin D3 (cholecalciferol). Vitamin D3 is an essential factor in the mineral balance, which regulates the calcium concentration in the blood and is involved in enchondral ossification (ossification). This is where the therapeutic importance of this UV light therapy lies. Cholecalciferol has to be activated from cholesterol under the influence of UV-B radiation, which is also contained in sunlight. If oral administration of cholecalciferol is not possible, UV light therapy can stimulate the increased formation of the body's own cholesterol.
  • UV-C radiation (200-280 nm) - This UV radiation also causes erythema, affects the bacterial flora of the skin and can cause light conjunctivitis (conjunctivitis caused by light).

In order to ensure safe use of UV light therapy, the so-called MED (minimum erythema dose) is first determined. For this purpose, sensitive, usually light-protected skin (e.g. on the forearm) is illuminated with different radiation intensities. After 24 hours, the erythema (reddening) is assessed and the therapy is individually tailored.

Your benefit

UV light therapy is also used, among other things, for diseases that are triggered by a vitamin D deficiency. This therapy can be particularly useful in patients who cannot take cholecalciferol orally (e.g. bedridden patients who cannot receive enteral care).


  1. Heisel J: Physical Medicine. Georg Thieme Verlag 2005


  1. S1 guideline: UV phototherapy and photochemotherapy. (AWMF registration number: 013-029), August 2015 long version

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