What causes the common cold?
A virus — actually, about 200 different viruses — causes the common cold. Contrary to popular belief, we seldom catch a cold from airborne particles expelled when someone with a cold coughs or sneezes. However, we easily pick up cold-causing viruses through hand-to-hand contact with someone who has a cold or from objects (e.g., doorknobs) that have been contaminated. This underscores the significance of hand washing.
Viruses act by infecting a host body's healthy cells and using those cells' reproductive machinery to make more viruses. At some point, the cells burst and die — letting all the new little viruses loose to infect even more of the host's cells. The destruction of cells lining the throat and respiratory tract causes the sore throat, cough, and runny nose characteristic of a cold. Fever, aches, and fatigue actually result from the body's immune response to the virus.
Antibiotics won't help if you have the common cold, but getting plenty of rest and fluids might. You can also try a steam treatment or some over-the-counter medications like decongestants to relieve your symptoms. See the related questions for more "cold," hard facts.