Read archived articles written by Palo Alto Medical Foundation doctors.

Mucus!

Why does my nose run on cold mornings?

Can I just say that how the nose works is really amazing? I set off to find out why my nose runs in the morning when I ride my bike to work, even if I do not have a cold or allergies, and found out some cool stuff.

Pints of Mucus

First, here is a gross, but interesting body fact for every preteen -- our bodies make about a quart of mucus each day. The purpose of the mucus is to keep the respiratory tract clean and moist. It does not usually make your nose run, it just drains into your throat and you swallow it. However, when you go outside into the cold weather, your nose tries to warm the cold air, dilating tiny blood vessels under the mucus-secreting glands. This increases the blood supply to your nose, which increases the amount of mucus produced -- how cool is that?

But why does it drip?

Since only so much mucus can drain into your throat to be swallowed, the rest comes out your nose. This is why your nose drips on cold days. OK, call me silly, but I think this is a really interesting factoid!


Last reviewed January 2008