Julie Fallon, (of Ardgowan School, asks :-

Why can we have mucus in our nose when we don't have a cold?

Philip Bagshaw, of the Department of Surgery, Christchurch School of Medicine, responded.

Mucus is normally secreted into the breathing passages of healthy people. It acts there as a blanket to protect against damage from bacteria and other particles which are breathed in during respiration. The protective mucus is moved out of the breathing passages by special cells which have minute hair-like projections called cilia. These beat rhythmically to move the mucus on. Once it enters the throat the mucus is then swallowed.

The mucus layers have other protective roles. For example, it stops the cells lining the air passage from drying out.

When we have a cold or other infection of the lungs or air passages, the rate of production of the protective mucus is increased, and we all know of the large amounts produced when we have a cold. We are usually unaware, however, of the small amount which is always present when we are healthy.