Although many people are convinced that a cold results from exposure to cold weather, or from getting chilled or overheated, these conditions in fact have little or no effect on the development or severity of a cold. 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. How colds are spread. Touching infectious respiratory secretions on the skin and on environmental surfaces and then touching the eyes or nose.