What side effects can ampicillin cause?
Ampicillin is a penicillin-class antibiotic, and its side effects usually fall into a few common groups: gastrointestinal effects, skin reactions, and allergic reactions. The most important risks are allergic reactions and severe diarrhea.
Common side effects include stomach-related symptoms such as nausea and diarrhea, and sometimes rash. Skin rash can be mild, but it can also be an early sign of a more serious drug reaction.
What serious allergic reactions should you watch for?
Ampicillin can cause an allergy. Get urgent medical help if you have signs of a serious reaction, such as:
- Trouble breathing, wheezing, or swelling of the face, lips, tongue, or throat
- Widespread hives
- Severe dizziness or fainting
If you develop a rash with fever, blistering, peeling skin, or sores in the mouth/eyes, seek urgent care, because these can signal a serious skin drug reaction.
Can ampicillin cause severe diarrhea?
Yes. Antibiotic-associated diarrhea can occur with ampicillin. Seek medical care if you have:
- Severe or persistent diarrhea
- Diarrhea with blood or mucus
- Fever or significant stomach cramps
These symptoms can be related to a potentially serious intestinal overgrowth that antibiotics can trigger.
What else might happen (less common but notable)?
Some people may experience:
- Yeast infection (for example, oral thrush or vaginal yeast) after antibiotic use
- Mild elevation of liver enzymes or other signs of liver irritation (uncommon)
- Headache or general body aches (less common)
Who is at higher risk of bad reactions?
Risk can be higher if you:
- Have a known allergy to penicillins or other beta-lactam antibiotics
- Have a history of severe drug rashes
- Have had antibiotic-associated severe diarrhea before
- Are taking other medicines that increase risk for certain reactions (for example, medication interactions can change side-effect risk)
When should you stop and call a clinician?
Stop taking ampicillin and get medical advice promptly if you develop:
- Breathing problems, facial/throat swelling, or widespread hives
- Severe blistering/peeling rash or rash with fever or sores
- Severe diarrhea, blood in stool, or diarrhea that doesn’t improve
If symptoms are mild (like mild stomach upset), contact your prescribing clinician for guidance, especially if symptoms worsen or don’t improve.
Are there alternatives if ampicillin doesn’t suit you?
If you can’t take ampicillin due to allergy or intolerance, clinicians may switch to another antibiotic class depending on the infection being treated and local resistance patterns. The right alternative depends on the cause of the infection and your allergy history.
Quick question to tailor the answer
What side effects are you seeing (rash, diarrhea, nausea, itching, breathing symptoms), and when did they start after starting ampicillin?