Antibiotics will fight bacterial infections, but they do not treat viral infections such as colds and the flu. If you have a viral infection, antibiotics will NOT make you better.
Antibiotics can destroy normal ("healthy") bacteria that live in your body. This can result in symptoms such as nausea, diarrhea, and vaginal yeast infections.
The overuse of antibiotics has played a role in the rise in drug-resistant bacterial infections. Taking antibiotics also poses a risk of allergic reaction, so they should not be taken when there is no possible benefit.
Anon JB. Upper Respiratory Infections. American Journal of Medicine. April 2010;123(4):suppl 1.
Lindell A, Kelsberg G, Safranek S. Antibiotics for viral upper respiratory tractinfections in children. Am Fam Physician. 2011;83(6):747-752.
Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.