What Causes Cold Symptoms
Cold symptoms are due mainly to the body's response to the infection. When a nasal cell is infected by a cold virus, the body responds by activating parts of the immune system and some nervous system reflexes. (5)
The immune system contains a variety of natural substances called inflammatory mediators. Inflammatory mediators help protect the body from infection and other harmful events. Some inflammatory mediators are released when nasal cells are infected by a cold virus. The names of some inflammatory mediators involved in colds include histamine, kinins, interleukins, and the prostaglandins. (5, 16-19)
When activated by a cold virus infection, inflammatory mediators cause dilatation and leakage of blood vessels and mucus gland secretion. (5) Inflammatory mediators also activate sneeze and cough reflexes and stimulate pain nerve fibers. These events are what lead to the symptoms of a cold.
The activity of the inflammatory mediators is not necessary for recovery from cold virus infection. Twenty-five percent of people who acquire cold virus infection do not develop symptoms. (4) People without cold symptoms recover from the infection as well as those who have symptoms.
The individual symptoms of a cold are caused by the action of particular inflammatory mediators, although there is some overlapping. (5) This has important implications for developing and selecting effective cold treatments.