Now that we have seen how the body reacts to attack, we can understand the symptoms of common cold.
First there is discharge from the nose accompanied by feeling of stuffiness which is only temporarily relieved by blowing. This is caused by inflammation of the nasal mucous membrane in its response to germ invasion. In the early stages the ordinary inflammatory fluid appears, formed by lymph and white cells attacking the germs. As the membrane is on the surface this discharge flow freely down the nostrils. It is sticking because of the presence here of the characteristic mucous which, as we have seen, normally helps to protect the membrane against infection.
As the cold progresses, the discharge becomes thicker and may be yellow. When this happens the second stage of inflammation has reached and pus is present. The pus, too, can escape down the nostrils so that there will be no symptoms of abscess formation.
A complication of the cold may, however, occur if the sinuses or hollow air-chambers communicating with the nose become involved. Simple discharge forming in them drain freely through the nose, but when it becomes thicker, escape through the restricted communication becomes difficult and a painful abscess may form.
The stuffiness felt during a cold is due to swelling of nasal membrane and blockage due to the discharge. The inflammation also necessitates an increased blood supply to the area, and this contributes to the general feeling of congestion and may cause a red nose, which is a minor but disfiguring symptom.