What is "speleotherapy"

n. the use of the microclimate of salt caves and mines for the treatment of asthma

Speleotherapy (Greek σπήλαιον spḗlaion "cave") is the respiratory therapy involving breathing of the mineral infused air of a salt mine. Salt pipes are based on this therapy, and the therapie uses this same salt.

There are records of miners in Roman and medieval times showing improvements in their breathing and in their long term breathing endurance, but no one outside of some Olympic Athletes took much notice..