Modern use of salt therapy (halotherapy) started in Germany when Dr. Karl Herman Spannage noticed an improvement in the health of his patients after they hid in local salt caves to escape heavy bombing during WWII. Since then, many European spas and medical clinics have incorporated halotherapy into their practices. Himalayan salt caves are commonly found in Poland, Pakistan, Estonia and Germany.
In 1843, Dr. Felix Boczkowski believed the air in the Wieliczka Poland Salt Mine had healing effects on people with respiratory conditions. Today, the Wieliczka Salt Mine operates as the largest underground rehab and treatment center in the world.