[Arnold Rikli and the "atmospheric cure"].

Background: In the second half of the 19th century, the Swiss autodidact Arnold Rikli developed his concept of the "atmospheric cure" as part of naturopathic efforts and implemented it in Veldes (today Bled, Slovenia).

Objective: What concepts did Riki develop and what indications did he see. How is this to be assessed from today's perspective?

Materials and methods: Rikli's own writings are used to evaluate his "light air cure" as a form of phototherapy. Secondary literature is used to evaluate Rikli's status in his time as well as contradictions and ambivalences from a modern perspective.

Results: For Rikli, the central linchpin of naturopathy is the "light air cure", which he combined with hydrotherapy, physical exercise, phytotherapy, and vegetable nutrition. He was very active as a writer with 53 publications in books and magazines and thus gained a great deal of fame. His views were not without controversy. He appeared as an outspoken opponent of conventional medicine and was a declared opponent of vaccination. His merit was to bring "light therapy" into the focus of attention. In the years that followed, it was increasingly scientifically processed and used in conventional medicine, for example, in the treatment of rickets and tuberculosis. Since 1989, the Arnold Rikli Prize for outstanding leadership in the field of photobiology has been awarded in memory of the "father of phototherapy".

Conclusion: As a nonphysician, Rikli popularized phototherapy as part of a holistic treatment concept in the second half of the 19th century and at the beginning of the 20th century. He eventually helped it gain recognition in conventional medicine, which initially focused on its use in nonpulmonary tuberculosis. Rikli's partly pseudoscientific justifications of his treatment methods have hindered their acceptance in medicine. Nevertheless, he is also a pioneer of phototherapy from a modern point of view and developed his own hydrotherapeutic approaches. His activities were also aimed at the development of tourism in the region around Bled. The combination of physical medicine with physical exercise, vegetable nutrition and phytotherapy seems almost modern compared to the spa medicine of its time. This is also recognized by the Arnold Rikli Prize for Photobiology.