There are records of improvements in the breathing of miners in Roman and medieval times.
Dr Feliks Boczkowski – a physician at the Polish salt mine at Wieliczka – wrote in 1843 that the miners there did not suffer from lung diseases and his successor set up a spa based upon these observations. Modern use of this therapy started in Germany when Dr. Karl Hermann Spannagel noticed improvement in the health of his patients after they hid in the Kluterthöhle karst cave to escape heavy bombing. Since that discovery, the salt mines of Poland and Eastern Europe have become popular sanitariums, attracting visitors from around the world. But the difficulty of accessing these salt mines, as well as safety concerns and prohibitive costs, sparked the development of halo therapy: treatment in a simulated salt cave.
It is now practiced in England, Canada, USA, Slovakia, Poland, Ukraine, Hungary, Romania, Australia etc.