Do antibiotics have side effects? Any time antibiotics are used, they can cause side effects. However, antibiotics can save lives. When you need antibiotics, the benefits outweigh the risks of side effects. If you don’t need antibiotics, you shouldn’t take them because they can cause harm. Common side effects of antibiotics include: rash, dizziness, nausea, yeast infection, and diarrhea. Get immediate medical help if you experience severe diarrhea. It could be a symptom of a C. difficile infection (also called C. diff), which can lead to severe colon damage and death. People can also have severe and life-threatening allergic reactions. One out of five medication-related visits to the emergency room are from reactions to antibiotics. If you experience side effects, follow up with your healthcare professional. To learn more about antibiotic prescribing and use, visit www.cdc.gov/antibiotic-use or call 1-800-CDC-INFO.