To help keep your lungs clean, your nose naturally produces about a quart of nice, sticky mucus (aka “snot” or “boogers”) every day to help trap dirt and germs in the air you breathe. Most of the time, this mucus just drains into your throat and you hardly know it’s there. But when it’s cold outside, have you ever noticed that your nose seems to produce even more mucus than usual (often enough that you have to grab a tissue)? Why does cold weather make your nose run away with itself??
The reason your nose runs when it’s cold is that your body is trying to warm up all of that cold air! When you encounter cold temperatures, the blood vessels in your nose naturally expand and get bigger. Blood vessels are the tiny passageways all over your body that help to circulate your blood, and even when you can’t see them (such as in your nose!), they’re always there, working hard!
When the blood vessels in your nose expand, they help to warm up the cold air you’re breathing in. But while they’re expanded, they also produce more mucus than when they’re smaller. Because this extra mucus is more than the daily dose your body is used to handling, it often drips out of your nose rather than draining down your throat, causing your nose to run! As soon as you reach a warmer temperature, your nose will usually stop running almost right away – the blood vessels contract again and the extra mucus production is shut down!