Colds and flu are caused by viruses. These viruses work by getting into your body, attacking your cells and using them to build more identical copies of themselves. This causes the familiar miserable symptoms of colds and flu, such as a runny nose, sneezing, a sore throat and a high temperature. Antibiotics don't work against viruses, and there is nothing you can do to cure a cold or flu. You have to wait for your body to fight and destroy the virus itself. However, you can relieve the symptoms and make yourself feel more comfortable while your body fights the virus. Ask your pharmacist for advice on treating the symptoms of colds and flu.