Craig: Hi, I'm Craig, I'm terrible at fake sneezing, ha-choo, and this is mental_floss on YouTube. Today, I'm going to answer Jacob White's Big Question, "Why does my nose get runny when I'm cold?"

So this phenomenon actually has a fancy name, cold-induced rhinorrhea. It also has a less fancy name, Skier's Nose, and I'm gonna talk a little bit about that today. Let's get started.

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Cold-induced rhinorrhea, or CIR, is a very common phenomenon, some people even experience sneezing and itching in addition to a runny nose. A 1991 study that examined medical patients at a ski resort clinic found that 96% of patients had experienced CIR, I'm experiencing it a little right now, though I should note that in this study, the percentage might be a little higher than average, because exercise also causes rhinorrhea. Rhinorrhea, by the way, is a medical term for a runny nose. But we should all say rhinorrhea from now on, 'cause it's hilarious.

Anyway, it turns out that the nasal mucus actually has an important job: protecting things like lung tissue. Basically, when you inhale air, the mucus warms that air up to your body temperature. This is gross. That keeps the sensitive areas of your body, like your lungs, protected from the cold. So every day, your nose creates a little less than a Liter of mucus or fluid, and nasal mucus is always coating your nasal cavities, but they dry out faster when you're in cold or dry climates. The nasal cavity produces extra mucus in those situations, 'cause you can never have enough mucus, am I right? It manages to do this by increasing blood flow in the nose. The blood flow goes back to normal pretty immediately after you enter a warmer place.

You might be relieved to hear that it's not all just mucus pouring out of your nose, though. Some of the wetness you experience on your nose is just water vapor. In cold temperatures, the air that comes out when you exhale is warmer than the air outside. Then, that breath condenses into fluid on the tip of your nose.

So, is CIR preventable? Well, the study that I mentioned earlier found that 92% of CIR sufferers who took a nasal spray containing atropine sulfate and saline saw an improvement in their symptoms, or if you wear a scarf over your nose, you'll breathe in air that's a little warmer and reduce the runniness, duh. Wear a scarf.

Thanks for watching mental_floss on YouTube, which was made with the help of all of these rhinorrheas. If you have a big question of your own that you'd like answered, leave it below in the comments. I'll see you next week.