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Is there a mother out there who doesn't warn their children that going out in the cold is going to make them sick? Have you heard that old chestnut about losing all of your body's heat through your head? Do you think drinking alcohol will warm you up?

All myths! We'll discuss them on this week's Healthcare Triage.

For those of you who want to read more, go here:

John Green -- Executive Producer
Stan Muller -- Director, Producer
Aaron Carroll -- Writer
Mark Olsen -- Graphics
Aaron Carroll:
   Is there a mother out there who doesn't warn their children that going out in the cold is gonna make 'em sick? Do you think that drinking alcohol will warm you up? Myths about cold weather are the subject of this week's Healthcare Triage. 
   [Healthcare Triage Intro]

   Myth! Going out in cold weather makes you more likely to get sick.
   What's up with this belief? Do people think the cold hurts our immune system and makes us more susceptible to getting sick? 'cause the opposite seems to be true. In a small study of how the body's immune system reacts to cold exposure, scientists actually found that the immune system was stimulated when people were exposed to the cold. The cold increased the number and the activity level of some of the body's key sickness-fighting cells, things like leukocytes, granulocytes, natural killer cells, and other chemicals necessary to fight off infection. So, cold weather actually may help your body to fight getting sick. 
   So why do people seem to get sick more in the winter? Well, one explanation is that people spend more time indoors when it's cold outside. They stay in relatively close proximity to each other. That allows them to pass colds and other viruses around with their sneezing and coughing. So staying inside may actually make things worse.
   Myth! Bundling up makes it less likely that you'll get a cold. 
   There are days even I'm amazed at what gets studied. To the research!
In a study published back in 1958, volunteers were divided into two groups. One group had to sit in very cold conditions but were allowed to wear warm coats. The second group had to sit in their underwear in 60-degree temperatures, and a third lucky group hung out in a balmy 80 degrees of warmth. Then all of them had a sick person's mucus dripped into their nose. Yes, maybe someday you'll be lucky enough to enjoy a glamorous career in science. 
   Anyway, it turns out that it didn't matter at all how cold it was or what you were wearing. Everyone with the virus stuck into their nose had the same risk of getting sick. The temperature and what you were wearing made no difference at all. 
   Myth! Going out wet makes you more likely to get a cold.
   Again, I'm not condoning this research, but let's go to it anyway.
   1968, a study was published in the New England Journal of Medicine that looked at inmates in Texas prisons. They were put in all kinds of temperatures and all kinds of dress. They were even put in water baths at near-freezing temperatures. And then cold virus was put into their noses. And it made no difference at all. Infection rates were similar, no matter how damp you were. Wetness and wet hair makes you no more likely to get sick.
Now, there was a similar study published in 2005 in the Journal of Family Practice. They randomized 180 people to either go about their business, or have their feet placed in water at 10 degrees Celsius for 20 minutes. And that's all! No infections were introduced.
   Later, it turned out that those who had their feet chilled were more likely to report cold symptoms later on. Some touted this as evidence that cold, wet feet made you more likely to get a cold. But this study didn't look at infection, it looked at reported symptoms. It could be that people just noticed their runny nose more because they remembered how cold their feet were and were terrified about getting sick. There's no evidence to prove you're more likely to get a cold from letting a part of you get wet and cold. Yeah, the older studies are, well, older, but they're exactly how you'd design a trial if you wanted to test this hypothesis. Look, I don't know who volunteered to have mucus put in their nose, but they went ahead and did it. Let's take their work and accept it.
   Myth! Drinking alcohol warms you up. Okay, let's start with those Saint Bernards running around with casks of alcohol around their neck. First of all, do they think people get lost in the Alps with mugs? And why barrels? Why not a blanket? First aid kit? Maybe materials to start a fire? Plus, it's a total myth that drinking alcohol warms you up.
  Alcohol lowers the vasoconstriction threshold, and leaves you vasodilated. In other words, you get more blood rushing to your skin. This might make you feel warmer in the very short run. But in the long run, it does the opposite. All that blood exposed to the cold means that it gets cooled off. That lowers your core body temperature, it doesn't raise it. And of course there's research!
  A study published in the British Journal of Clinical Practice in 1995 got a bunch of men to drink either alcohol or placebo and then immersed them in cold water for an hour. When they drank the alcohol, their temperatures went down more, by a bit. A similar study published the next year tried to quantify this effect. It also found that drinking alcohol led to a lower overall core temperature, but again, the difference is pretty small. They concluded that the idea that drinking might lead to hypothermia (which many also think is a real thing) is likely also untrue. But there's no evidence for alcohol warming you up, and some minimal evidence for it doing the opposite. Myth busted.

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