Finsen light

The finsen light is named for its inventor, Niels Tyberg Finsen (1860-1903). It was a powerful light used to cure people of the skin disorder lupus.

Ultraviolet Light (UV)

Finsen received his medical degree in 1891. Over time, he became very interested in how light affects disease. Finsen was familiar with the work of a Swedish researcher who in 1889 had discovered the effects of ultraviolet light. The researcher had found that short-wave ultraviolet (the range of radiation wavelengths just outside the color violet in the visible spectrum) light irritated biological tissue more than the longer-waved infrared light.

With this information at hand, Finsen began recording the effects of sunlight on insects and amphibians. He was convinced that light could be used to treat human disease. Finsen found that ultraviolet light from the sun or from electric lights could kill bacteria. He wrote several papers in 1893 and 1894 on the beneficial use of phototherapy.

In 1895 Finsen made an arrangement with Copenhagen Electric Light Works to treat patients two hours each day with ultraviolet light. His patients were diagnosed with lupus vulgaris. This is a skin disease caused by the tubercle bacillus (tuberculosis). Finsen designed a powerful lamp (the finsen light) for the treatment. It was a bright artificial light generated by electrical carbon arcs.


In 1896 Finsen founded the Finsen Institute for Phototherapy in Copenhagen. The Institute was dedicated to studying effects of light and curing people of disease. At the Institute, 800 lupus patients were treated. Half were cured of the disease and nearly all the rest showed improvement in their conditions. For this achievement Finsen was awarded the 1903 Nobel Prize in medicine. Finsen donated half the prize money to the Finsen Institute.

During Finsen's era both X-rays and gamma rays were discovered by the German physicist Wilhelm Rontgen (1845-1923) and the French physicist Antoine-Henri Becquerel (1852-1908). With Finsen's success in light therapy leading the way, the idea of radiotherapy was born. Since Finsen's time, X-rays and gamma rays have been frequently used for the diagnoses and treatment of disease.

Even today some foods are irradiated with ultraviolet light to kill bacteria. Finsen was also ahead of his time in his concept of the effect of sunlight on disposition and health. It is only fairly recently that Seasonal Affective Disorder (SAD) has been recognized as a type of depression caused by a lack of sunlight in winter. People diagnosed with SAD can be treated by sitting under lights to extend their exposure to light on short days.

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Read this paper:
How Finsen's light cured lupus vulgaris.
Møller KI1, Kongshoj B, Philipsen PA, Thomsen VO, Wulf HC.
Photodermatol Photoimmunol Photomed. 2005 Jun;21(3):118-24.

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