Why Your Nose Gets Runny When It is Cold

Daven Hiskey 12
Today I found out why your nose gets runny when it is cold.

On an average day, a typical person’s nose will produce about one quart of mucus/fluid (just under one liter).  Most all of this snot generally gets passed back into your throat and swallowed, often without you even really being too conscious of it.  When you’re breathing cold air though, the rate of mucus production goes up significantly, causing some of that snot to come out the front of your nose, rather than back in your throat.

What’s going on here is the blood supply to your nose actually increases as a response to the cold air, via tiny blood vessels in your nose dilating to increase the blood flow.   This helps keep your nose warm as you breathe, as well as begins to warm the cold air you’re breathing before it enters your lungs.

This increased blood flow doesn’t just help warm the air though, it also has a side effect of providing a lot more blood than normal to the glands which produce the mucus in your nose.  This, in turn, causes them to start producing snot at a much higher rate than normal, which causes your nose to run when you’re breathing the cold air.

Once you’re back in a warm air environment, the blood vessels in your nose will constrict and the glands that produce the mucus/liquid mix will go back to their normal rate of around four cups of snot per day.

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Bonus Facts:

  • Your nose runs when you’re crying because the tears from the tear glands under your eyelids drain into your nose, where they mix with mucus to form very liquidy snot.
  • Allergies can cause your nose to run because the body reacts to them the same way it reacts to viruses and the like.  Namely, by kicking the mucus glands into overdrive to try to stop as much of the allergen as possible from entering your body.
  • As alluded to, the same type of thing is happening when you get a cold or similar sickness.  The body increases mucus production rate to try to keep as many of the germs as possible out of your body.

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  1. frogagog November 3, 2011 at 11:18 am - Reply

    My takeaway: A typical person drinks around four cups of snot per day.

    • Daven Hiskey
      Daven November 4, 2011 at 12:49 am - Reply

      @frodago: delicious… ;-)

    • Reuben January 8, 2015 at 4:27 am - Reply

      My takeaway is that there’s nothing disgusting about picking your nose and then eating your snot, because you ingest most of it anyway. It’s way more disgusting to leave it on a tissue, or anywhere else outside your body.

  2. Joe Rosselini March 23, 2012 at 6:05 pm - Reply

    Actually, that does not sound correct at all. I’ve learned before that on a cold enviroment, your blood vessels will, in fact, constrict. This happens because then you will have a lower contact surface causing your body to loose less heat, keeping you warm. The contrary is also true. Can I have some answer about this from someone that has true knowledge about this stuff (I don’t) ?


    • Daven Hiskey
      Daven April 19, 2012 at 4:54 pm - Reply

      @Joe: It may not sound correct, but it is. Check the sources for more information.

    • tlhonmey September 16, 2014 at 5:35 pm - Reply

      The blood vessels in your skin and to your extremities constrict when you get cold to reduce heat loss. One of the primary purposes of your nose however is to pre-condition the air before it gets to your more sensitive throat and lung tissues. Just try taking a breath through your mouth when it’s below freezing out and you’ll see what I mean.

  3. Amanda September 23, 2014 at 9:04 pm - Reply

    Yes, but why does my nose run when I’m really tired?

  4. cece January 6, 2015 at 8:22 pm - Reply

    So if I breath hot air then my nose won’t run? Because I have a cold right now and my nose iis running a marathon and it is starting to get annoying. I hate being sick but I’d be ok with just my sore throat if my nose would stop constantly leaking.

    • Adam January 20, 2015 at 5:53 pm - Reply

      Unfortunately, no. Breathing cold air through your nose is just one cause of a runny nose. Having a cold is another cause of a runny nose.

      Eliminating one cause of a runny nose won’t prevent a runny nose if another cause is still in effects.

      Recover from your cold, keep your nose warm, and if thre is nothing else causing your runny nose it should clear up.

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