How common is change in bowel habits in immunotherapy side effects?

Immune-based cancer treatment can activate immune cells against healthy tissues as well as cancer cells. When the bowel is affected, symptoms may range from mild changes in stool to frequent diarrhoea, abdominal pain, or blood or mucus in the stool.

Infection, antibiotics, diet, stress, and other medicines can cause similar symptoms. Timing and severity matter, but the symptom alone cannot confirm an immune-related reaction. Your oncology team may ask about bowel movements and arrange tests before recommending treatment changes.

Contact your oncology team promptly about any new bowel change during or after immunotherapy, even if it seems mild. Record when it began, stool frequency and appearance, urgency, pain, fever, blood, and what you can drink.

Take only the medicines advised by your treatment team. Do not stop immunotherapy or begin anti-diarrhoeal treatment without instructions, because the safest approach depends on the suspected cause and severity. Keep drinking fluids unless a clinician has restricted them.

Seek urgent care for severe or rapidly increasing diarrhoea, inability to keep fluids down, dizziness or fainting, severe abdominal pain, fever, black stools, or visible blood. Tell the team that you are receiving or recently received immunotherapy.

Ask whether your symptoms could be immune-related, which warning signs require emergency help, and what to record at home. Ask whether you should change food, fluids, or medicines while the team investigates.