Do I really need antibiotics? Say yes to antibiotics when needed for certain infections caused by bacteria. Say no to antibiotics for viruses, such as colds and flu, or runny noses, even if the mucus is thick, yellow or green. Antibiotics also won’t help for some common bacterial infections including most cases of bronchitis, many sinus infections, and some ear infections. Antibiotics are only needed for treating certain infections caused by bacteria. Antibiotics do NOT work on viruses. To learn more about antibiotic prescribing and use, visit www.cdc.gov/antibiotic-use