(HealthDay News) -- Antibiotics can help you recover from a bacterial infection, but they offer no medical benefit against viruses.

Prescribing an antibiotic for an viral illness, in fact, isn't a good idea. Overuse of these medicines can make the bacteria in your body resistant to the drugs. The medicines then lose their effectiveness, making a bacterial illness harder to treat.

The American Academy of Family Physicians lists these illnesses that are often treated with an antibiotic, and a few that don't need the medication:

• Colds and flu are caused by viruses, and won't respond to antibiotics.
• Cough and bronchitis are usually caused by viruses. However, people with chronic lung problems or those who have a cough that lasts a long time may need antibiotics.
• While a regular sore throat is caused by a virus, strep throat is a bacterial infection that requires antibiotic treatment.
• Ear and sinus infections should be evaluated by a doctor, since many are caused by bacteria, while others are viral.