Salt therapy, halotherapy or speleotherapy[1] is the use of salt mines, caves or other forms of exposure to salt air in the belief that this confers a health benefit.
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These natural deposits of mineral halite are derived from evaporated ancient lakes and seas. The unrefined rock salt, primarily sodium chloride, also includes varying concentrations of other mineral salts such as calcium and magnesium, manganese and sulfates which have additional therapeutic properties, depending on the source.
The special characteristics of the micro-climate of a salt mine include stable air temperature, humidity and lack of airborn pollutants such as pollens, and is unique to each mine. At depth the air pressure is also significantly higher than above ground which has been found to benefit sufferers of respiratory diseases in studies conducted at the Dead Sea which is below sea level.
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.[2] Modern use of this therapy started in Germany when Dr. Karl Hermann Spannagel[3] noticed improvement in the health of his patients after they hid in the Kluterthöhle karst cave to escape heavy bombing. It is now practised in places such as Bystrianska in Slovakia,[4] Wieliczka in Poland[5] and Solotvyno in Ukraine.[6]
Halogenerators are used to simulate the salted atmosphere of salt mines. These highly developed machines crush rock salt into dry micrometre sized particles, ionize the particles, and release them into the air. Salt particles of sizes 0.1-2.5 micrometres are able to escape the natural defences of the upper airways and travel deep into the lung to the level of the alveoli. Typically used in a small room with floors and walls lined with rocksalt.
Salt lamps are another method of ionizing rocksalt. A large crystal of natural salt is hollowed out and heated with a tealight or lightbulb. The crystals give off an attractive glow in various colours of pink, orange, red or purple according to the minerals present.
Instead of entering a salt mine, the benefits of salt may allegedly be reproduced by breathing through a pipe packed with salt crystals.[7] Composition of the salt crystals used in the Hungarian Sopipa - NaCl 98,7% CaSO4 0,1% MgCl2 0,028 %, CaCl2 0,13% Fe2O3 0,00056%, and in even smaller amounts: K, I, Br.
Breathing an aerosol of hypertonic salt water (3-7% NaCl) has been found effective as a treatment for the heavy build up of mucus typical of cystic fibrosis.[8] The benefits of this were first noticed by sufferers who regularly surfed in Australia and so were exposed to the natural aerosol of the salt spray.[9]
The use of saline solution delivered by a nebulizer to treat bronchiolitis in children has also been systematically reviewed. The conclusion was that, "Current evidence suggests nebulized 3% saline may significantly reduce the length of hospital stay and improve the clinical severity score in infants with acute viral bronchiolitis."[10]