There are at least two good reasons to try a cold shower or bath. The cooler temperature saves energy and research says it may help reduce the risk of catching a cold by 40 percent. If total immersion isn't for you, try alternating cold and warm water foot baths: Fill two tubs with water, one at around 70 degrees (temperatures lower than that aren't advised for at-home foot baths), the other around 100 degrees. First place both feet into the warm bath and let them soak for three minutes. Afterward, move feet into the cool water for one minute, then place them back into the warm water. Repeat this jump from warm to cold water three times.
Icy plunges into the Danube River are what are said to have helped Sebastien Kneipp, a 19th century German priest and pioneer of hydrotherapy, cure himself of tuberculosis. These cold-water immersions would slow his circulation, then as he got out and warmed up, it gradually increased again.
"Training" the blood vessels in this manner is believed to strengthen the body and help it fight off illness, which is the theory behind the alternating hot and cold soaks offered at bathhouses in various countries in Europe.