In this article, the author discusses how to tell the difference between a cold and airborne allergy symptoms. A cold is caused by a viral infection. Viruses spread through an infected person's cough, sneeze, handshake, or contact with a contaminated surface. When a virus enters one's body, his/her immune system reacts. This produces the symptoms that people associate with colds: sore throat, sneezing, runny nose, fever, headache, cough, and body aches. Meanwhile, an airborne allergy is caused by exposure to an "allergen"--the most common of which is pollen; other allergens include dust mites, animal dander, mold, and fungi. The key difference between a cold and an airborne allergy is the amount of time one's body is affected. A cold typically lasts for seven to nine days, while allergy symptoms may last much longer. (Contains 1 figure.)