Actinotherapy (Greek, aktis, aktinos—a ray; therapeia—"a healing") is defined by Beckett1 as "the therapeutic use of nonionizing radiations similar to those found in sunlight, but produced by artificial sources, and dealing particularly, on the one hand, with ultraviolet radiations of a wave length less than 3200 Angstrom units, and, on the other hand, with infrared radiations greater than 8000 Angstrom units, up to 40,000 Angstrom units."
The "healing power" of the sun was recognized in ancient times. Some of the highlights in the development of modern actinotherapy1 are the following: 1800: Herschel discovered that at one end of the visible spectrum there were radiations which were not perceptible to the human eye, but which caused an elevation of temperature (infrared rays). 1801: Ritter demonstrated the existence of rays beyond the violet end of the visible spectrum, which could be detected by changes produced in
SULLIVAN M. ActinotherapyWhat Are Its Indications in Dermatology?. AMA Arch Derm. 1957;76(5):634-647. doi:10.1001/archderm.1957.01550230100015