Colds occasionally can lead to secondary bacterial infections of the middle ear or sinuses, requiring treatment with antibiotics. High fever, significantly swollen glands, severe facial pain in the sinuses, and a cough that produces mucus, may indicate a complication or more serious illness requiring a doctor's attention. How Cold Viruses Cause Disease Viruses cause infection by overcoming the body's complex defense system. The body's first line of defense is mucus, produced by the membranes in the nose and throat. When a virus penetrates the mucus and enters a cell, it commandeers the protein-making machinery to manufacture new viruses which, in turn, attack surrounding cells.
Cold symptoms are probably the result of the body's immune response to the viral invasion.
Virus-infected cells in the nose send out signals that recruit specialized white blood cells to the site of the infection. In turn, these cells emit a range of immune system chemicals such as kinins. These chemicals probably lead to the symptoms of the common cold by causing swelling and inflammation of the nasal membranes, leakage of proteins and fluid from capillaries and lymph vessels, and the increased production of mucus. Kinins and other chemicals released by immune system cells in the nasal membranes are the subject of intensive research. Researchers are examining whether drugs to block them, or the receptors on cells to which they bind, might benefit people with colds.