Hot Springs

My wife and I took a quick break at Gold Fork Hot Springs, south of McCall, Idaho. The hot springs are laced with lithium salts, but I began to wonder if the more profound healing effects of hot mineral waters are due to the warming of inflamed, or perhaps chilled and hibernating, bodies.

The heat sensors in your skin respond to vanillin-like molecules, e.g. hot pepper capsaicin, or elevated temperature to cause a sensation of warmth. Thus the vanillin receptors are proteins embedded in the membranes of nerves and they bind the molecules of the appropriate shape, the receptors change shape and start an electrical signal that moves to the brain. We experience that as warm or hot, depending on the intensity of the signal.

The nervous system also responds by a returning nerve signal that releases anti-inflammatory hormones in the tissue from which the original hot signal arose. This is the reason that heat applied to an inflamed wound will reduce swelling, redness, etc. Capsaicin or castor oil applied to the same general area will also reduce inflammation, because capsaicin and castor oil (ricinoleate) bind to the same vanillin receptors.

I think that hot springs are anti-inflammatory, because they stimulate vanillin receptors over a large portion of skin and stimulate body-wide suppression of inflammation. This would suggest that many inflammation-based diseases would benefit from hot springs, saunas, sweat lodges and other types of heat treatments. Because cold/menthol receptors are involved in a parallel anti-inflammatory response, the sauna to snow alternation may make a lot of sense for reducing chronic inflammation.

Fever and chills may also be related to these effects. Sudden shifts in the temperature of tissues may disrupt the equilibrium between the tissue and a quiescent pathogen. Heat treatments may similarly disrupt the chronic, bacterially-induced inflammation that some postulate to be the basis for many degenerative diseases.