Antibiotics

Source: MedlinePlus Health Topics, U.S. National Library of Medicine

Last synced 8/9/2026Status: primary verified

What are antibiotics? Antibiotics are medicines that fight bacterial infections in people and animals. They work by killing the bacteria or by making it hard for the bacteria to grow and multiply. Antibiotics can be taken in different ways: Orally (by mouth). This could be pills, capsules, or liquids. Topically. This might be a cream, spray, or ointment that you put on your skin. It could also be eye ointment, eye drops, or ear drops. Through an injection or intravenously (IV). This is usually for more serious infections. What do antibiotics treat? Antibiotics only treat certain bacterial infections, such as strep throat, urinary tract infections , and E. coli . You may not need to take antibiotics for some bacterial infections. For example, you might not need them for many sinus infections or some ear infections . Taking antibiotics when they're not needed won't help you, and they can have side effects. Your health care provider can decide the best treatment for you when you're sick. Don't ask your provider to prescribe an antibiotic for you. Do antibiotics treat viral infections? Antibiotics do not work on viral infections. For example, you shouldn't take antibiotics for: Colds and runny noses, even if the mucus is thick, yellow, or green Most sore throats (except strep throat) Flu Most cases of bronchitis What are the side effects of antibiotics? The side effects of antibiotics range from minor to very severe. Some of the common side effects include: Rash Nausea Diarrhea Yeast infections More serious side effects can include: C. diff infections , which cause diarrhea that can lead to severe colon damage and sometimes even death Severe and life-threatening allergic reactions Antibiotic resistance infections Call your health care provider if you develop any side effects while taking your antibiotic. Why is it important to take antibiotics only when they're needed? You should only take antibiotics when they are needed because they can cause side effects and can cont

Educational only

This information is for general education and is not medical advice. Always talk to a licensed U.S. clinician about your situation, medications, or treatment decisions.