In fact, such a quick exposure could lead to body signals getting mixed up, he said. When cool water splashes a highly sensitive area like your face with lots of nerve endings, you may not sense that you're overheating.
Longer exposures, though, may be beneficial in certain situations: For exertional heat stroke, for example, the best way to quickly lower body temperature is to submerge yourself in cold water -- up to the neck -- for at least 10-15 minutes, he said. There's also evidence that it prevents delayed onset muscle soreness, probably because changing the muscle temperature lessens the damage of overheated cells in the muscle.
Some health and fitness gurus say cold water can improve blood circulation. Depending on the application method, that could be true -- at least temporarily, said Thomas Swensen, professor and chair in the Department of Exercise and Sport Sciences at Ithaca College.
"What they're talking about is reactive hyperemia," he said. "Think about when you were little and came inside after being in the snow all day long. You took a hot shower and it felt like your toes swelled up. That was the circulation returning." In order to reduce inflammation, then, repeated applications of ice water would be necessary.