A contrast bath, also called hot/cold immersion therapy, is a method of treating soreness, swelling, infection and inflammation. It is useful for treating joint injuries, such as mild sprains, and can also ease the symptoms of chronic conditions such as carpal tunnel syndrome. Some athletes also use contrast bathing to speed up recovery from exercise. A contrast bath involves immersing the joint in alternating hot and cold water, which helps to increase blood flow to the area and accelerate metabolic healing. Contrast bath therapy also causes numbness in the joint or muscle and increases the elasticity of the ligaments, giving greater range of motion.

The process works through a repetition of two processes known as vasodilation and vasoconstriction. The hot water causes vasodilation, or the widening of the blood vessels, while the cold water causes vasoconstriction, which is when the blood vessels tighten. A contrast bath alternates between these two processes in order to create a pumping action in the area receiving the treatment. It is this pumping action that increases blood flow and helps to drain excess fluids out of a swollen joint or muscle.

In order to benefit from a contrast bath, first fill two separate basins; one with hot water and the other with cold. The cold water should be between 50° and 65° F (10° and 18° C) while the hot water should be between 100° and 110° F (38° and 44° C). Temperature will vary slightly depending on the comfort of the individual. Alternate between hot and cold baths using 3 minutes to 30 seconds. The temperature and time may be adjusted for certain individuals, such as children and those who are diabetic or have circulatory problems.

This sequence should be followed for 5-7 changes. The total treatment time will vary, but usually lasts around 30 minutes.