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Here's something tailgaters, ice skaters, skiers and other cold weather fans might want to keep in mind: Drinking boozy beverages will make you feel warmer, but it doesn't actually keep you warm or prevent hypothermia. Instead, drinking alcohol lowers the core temperature of your body.

According to Dr. William Haynes, director of Clinical Pharmacology at the University of Iowa, “Consumption of alcohol undoes many of the human body’s healthy reflexes, one of which is keeping the core body temperature warm in cold weather.” It doesn’t even take that much for this effect to kick in—just one alcoholic drink will start the process that results in a lowered core body temperature.

How does alcohol do this, and why does drinking alcohol make you feel warmer, even though you actually are getting colder?

You Booze, You Lose (Heat)

Alcohol is a vasodilator. It causes your blood vessels to dilate, particularly the capillaries just under the surface of your skin. When you have a drink, the volume of blood brought to the skin’s surface increases, making you feel warm. (That dilation is why slightly or exceedingly intoxicated people look flushed.) This overrides one of your body’s defenses against cold temperatures: Constricting your blood vessels, thereby minimizing blood flow to your skin in order to keep your core body temperature up.

Someone enjoying a drink in the cold may feel warmer from the extra blood warming his skin, but that blood will rapidly cool thanks to the chill in the air. Plus, the warmth caused by blood rushing to the skin will also make him sweat, decreasing his core temperature even further. The rapid drop often occurs without the drinker realizing it, because his skin will still feel fairly warm, which makes it doubly dangerous to drink alcohol in extremely cold weather. (You might want to put down the coffee, too; caffeine has a similar effect.)

The Big Chill

This isn’t the only bad thing about drinking alcohol in the cold. According to a study done by the Army Research Institute of Environmental Medicine, drinking alcohol in chilly weather also reduces the body’s ability and tendency to shiver, taking away yet another method your body uses to help keep warm when it is cold.

Bottom line? The age-old practice of drinking alcoholic beverages to keep the body warm in cold weather is the exact opposite of what you should do.