Why does my nose run when it's cold?

Charlene - Hi naked scientists. My name is Charlene, and my question for you is, why is my nose constantly running in cold weather? What is the physiological benefit of this? Thank you.

Rhys - It's an excellent question, Charlene, and I'm sure one that many of us can empathise with as colder temperatures begin to bite in the Northern Hemisphere in a bit. To answer it, we've enlisted the help of Neil De Zoysa, who's a consultant, ear, nose, and throat surgeon.

Neil - We need to have moist air in order to pull oxygen out of the air in our lungs, and our nose makes mucus in order to do that. In cold weather, the air is less moist, so the nose needs to compensate for that, and cold air in general is an irritant to the nose, so we make more mucus as a direct a response to it.

Rhys - So that's the reason why our noses run in cold weather. But what might the physiological benefits be?

Neil - It's an adaptive response to make the air more efficient for us to breathe in. The mucus contains antibodies, so it helps us fight infections. The other reason we get more infections in cold weather is because the lining of our nose has little hair cells in it, and they're less efficient in cold weather, so infections can build up within the nose.

Rhys - Fascinating stuff. That was the ear, nose and throat surgeon, Neil De Zoysa. My thanks to him and to all of you who got in touch with us on our forum to offer your thoughts on the role that mucus plays in helping fight infections. Next time we'll be heading into space to answer this question from listener. David,

David - What are black holes made of? Would it be based on subatomic particles?

Rhys - Thank you, David. My colleague James Tytko will be taking on this one next week. If you'd like to hazard a guess or you have a question of your own, please email us. That's chris@thenakedscientist.com, or send us your thoughts on our forum...