More than 110 viruses, known as rhinoviruses, can cause the common cold. An individual may develop a temporary immunity to one or two viruses and still be infected by another. Any time people are together, viruses that cause the common cold are present. Adults average two to three colds each year, and children experience six to ten. Colds can be contracted by shaking hands, sneezing, and breathing. Evidence indicates that hand-to-hand contact is the most common way a cold is spread. When infected individuals blow or touch their noses, the virus is transferred to their hands. When an uninfected person touches the infected person's hands, the virus is again transferred to the uninfected individual. Touching the face with hands that carry the virus leads directly to developing a cold. Frequent hand washing may prevent the spread of the virus. The signs and symptoms of a cold are easily recognized. They include a feeling of listlessness, general aches and pains, watery eyes, and runny nasal passages. As the cold progresses, the nasal membranes swell, resulting in a stuffy nose. Infections affecting the throat can lead to sore throats and coughing. These symptoms tend to last 7 to 10 days. As an old axiom points out, if a cold is treated, it will go away in 7 days, and left alone, it will last a week. A cold may occasionally persist for several weeks, but complications are infrequent in adults and older children. When they do occur, it is most often a middle ear or sinus infection. Antibiotics do not cure the common cold because they fight only bacterial infections. Over-the-counter decongestants-in spray or pill form-constrict blood vessels to shrink nasal swelling and open air passages, providing temporary relief of cold symptoms. Nasal sprays are more effective because they deliver a greater concentration of medicine to the nasal passages and give immediate relief. But their overuse can cause a rebound effect, making congestion even worse. Nasal sprays should not be used for more than consecutive days. Anithistamines are not very effective for cold symptoms and may lead to drowsiness. Cough suppressants, which may offer relief from nagging coughing episodes, should be used with caution. On the positive side the cough reflex is nature's way of clearing the lungs; on the negative side persistent coughing may irritate the airway. The pharmacist or medical doctor should be consulted to match the appropriate cough medicine with the type of cough (dry or loose mucus).The best advice for treating a cold is to take aspirin, ibuprofen, or acetaminophen (young children shouldn't take aspirin with cold symptoms because it may cause Reye's syndrome); drink plenty of fluids; eat a nutritious diet; and get plenty of rest.