There is no way to be certain what is causing the infection without taking a sample and having it cultured in a laboratory. Sinus infections can be caused by either bacteria or viruses. Antibiotics should be used only for a severe sinus infection, or one that lasts longer than two weeks, since bacteria may be the cause. Doctors frequently prescribe an antibiotic when they are not certain whether a patient's infection is bacterial or viral. Many times, taking medicines to alleviate symptoms and allowing your immune system to fight infection is more effective.
Unnecessary prescriptions are a major reason for the rise of antibiotic-resistant bacteria.
The CDC's Director of Antimicrobial Resistance, Dr. Richard Besser, says a common reason for unnecessary prescriptions is patient demand for treatment. Don't hesitate to ask your doctor whether he is fairly sure an antibiotic will work for you, or whether the main reason he is giving you a prescription is because he thinks you want one. If you are taking antibiotics, it is important not to stop before taking the full number of doses. Prescriptions are written to cover the time needed to help the body fight all the harmful bacteria. Stopping the medication early may let remaining bacteria restart the infection.