Why does a nose run when you have a cold?

Why does your nose run when you're out in the cold, even if you aren't sick?

• It makes sense that is would run when you eat hot food, but when its cold outside-like say 15 degrees-why does that thing drip?!!

• Answer:

  I used to wonder about that too. It's because the function of the nose is to filter, warm and humidify the air you breathe. It does this by increasing the flow of blood to the mucosa. By doing this it performs all three functions. The mucous cells swell and secrete mucous to humidify and filter the air and the increased circulation warms the nasal passages. The air can now enter your lungs without causing a reaction. Some people have asthma that is triggered by cold dry air. In cold, dry weather this system has to work overtime so you get excessive thin mucous production. Hope this helps you understand. God bless and keep you healthy.