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How long does it take do get sunburnt: Erythema-Dosimeter by Dr. Keller

When summer begins they are always around: Guidelines for sunbathing without getting sunburnt in order not to increase the risk of skin cancer.

Sunbaths in prescription used to be quite common around the year 1900. Mainly tuberculosis-infected persons are sent to so called heliotherapies in alpine sanatoriums, like St. Moritz in Switzerland.

Sun lamps emitting bright bright light and UV-radiation are used for ambulatory light therapy. This therapy is applied successfully to cure a variety of dieseases. Children suffering from rickets are treated often with light therapy. Rickets lead to a disruption during bone growth and deformed bones are the result. Regularly sunbaths under sun lamps help to cure rickets. The treatment is quite violent from our Point of view today. The skin is irradiated until it gets red and the patient gets sunburnt.

But how long does the radiation have to be to be "effective"? And does the sun lamp emit enough of the wanted UV-radiation?

The dermatologist Dr. Philipp Keller developed an Erythema (Redness) Dosimeter in the early 1920s. Light-sensitive test stripes are irradiated under different filters until they get stained. The time necessary for the staining and the different intensities of the staining are used to determine the irradiation time to cause redness. 

Today we know that vitamin D deficiency is the reason for rickets. Our body is able to synthesize vitamin D on ist own when we spend time outdoors in the sun. Rickets are treated with vitamin D supplements nowadays. Sun lamps are not used any longer as they might be responsible to promote the development of skin cancer.

This Erythema-Dosimeter belongs to the estate of Dr. Otto Nehrkorn (1908 - 1997). He was head of the x-ray department of the municipal hospital of Remscheid. He donated it to the Museum in 1957.