There is an urban legend that drinking alcohol keeps you warm. The legend is at least as old as the story of St. Bernard dogs, which are known to rescue lost travelers in the Swiss mountains. Edwin Landseer, in a portrait of one of those scenes, painted one dog with a barrel of mead hanging around its neck. The painting became popular and with its popularity people began to associate the dogs with carrying alcohol on their collars — as a cure to the cold — and since then, pop culture took up the idea. Many people still believe this as a true fact, so here's something especially tailgaters, ice skaters, skiers and other cold weather fans might want to keep in mind: Drinking booze 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 do you feel warmer, even though you actually are getting colder?
Alcohol is a vasodilator. It causes your blood vessels to dilate, mostly 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. (this is where your red cheeks come from when you drink) 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 minimize radiating heat away from your body.
If you enjoy drinking in the cold, you may feel warmer from the extra blood in your skin, but that blood will also radiate more warmth, leaving your body cooler (yeah, but that's not the cool you want to be). Plus, the warmth caused by blood rushing to the skin will also make you sweat, decreasing your core temperature even further.
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 to shiver, which is yet another method your body uses to help keep warm when it is cold.
Drinking in the cold becomes even more dangerous if you are in extreme freezing temperatures not close to a shelter. In this situation you totally need to avoid any alcohol or caffeine (which has a similar effect), to keep your body as warm as it can, also you need to be agile to find shelter as fast as possible, alcohol is not going to help in being agile.
In conclusion, the urban legend is false, alcohol undoes all the body’s defense mechanisms against losing heat. So if you used to drink while trying to keep yourself warm you were making your life even harder. From now on, you better bring a large warm coat with you when you go to a cold place instead of a bottle of booze.