Q: Why do our noses run when...

Q: Why do our noses run when it is cold?

A: Actually, our noses run almost all the time, but we don’t notice it, said Dr. Susan Stangl of UCLA. Every day, cells lining the nose produce about a quart of mucus that traps irritants and infectious agents and carries them down the back of the throat. Only when the amount increases, as in response to irritants such as dust, viruses or cold, does the brain become aware of the mucus.

Interestingly, Stangl said, scientists are not in agreement about whether a runny nose during a cold is strictly a defense mechanism to remove irritating virus particles from the nasal passages or whether it is the cold virus’ way of spreading to other people.