: the therapeutic use of water (as in a whirlpool bath)—compare hydropathy
External use of water for medical treatment. Wet heat helps relieve pain, improves circulation, and promotes relaxation. Wet cold causes blood vessels to close, reducing swelling and pain after injury. Underwater exercise helps strengthen weak muscles, restore joint motion after injury, clean and heal burned flesh, aid muscle function after stroke, and treat arthritic deformity and pain. Whirlpool baths and showers are also used. Hydrotherapy is usually employed by specialists in physical medicine and rehabilitation.