Are Immunotherapy Side Effects Normal, or Does It Need Urgent Attention?

Starting immunotherapy often brings a mix of hope and worry. Many people have heard that it is gentler than chemotherapy, so a new rash, loose stools or unusual tiredness can feel confusing. Is this simply part of treatment, or a sign that something needs attention?

The honest answer is that both are possible. Many immunotherapy side effects are mild and manageable. A smaller number can become serious if they are not recognised early. Knowing the difference, and knowing when to call your cancer care team, is one of the most useful things you can do during treatment.

Why Immunotherapy Side Effects Are Different

Immunotherapy works by helping your own immune system recognise and attack cancer cells. The most widely used type, called immune checkpoint inhibitors, releases the natural “brakes” that normally stop the immune system from becoming overactive.

This is what makes the treatment effective, but it also explains its side effects. Once those brakes are released, the immune system can sometimes attack healthy tissues as well. Doctors call these immune-related adverse events. They can affect almost any organ, most often the skin, bowel, hormone glands, lungs, liver and joints.

Unlike chemotherapy side effects, which often follow a more predictable pattern around treatment, immunotherapy side effects can start at any time, including weeks or months after treatment begins or even after it has finished.

Common and Usually Mild Side Effects

Many people experience only mild effects, or none at all. Common immunotherapy side effects include:

• Tiredness: Fatigue that can range from mild to significant.
• Skin changes: Itching, dryness or a rash.
• Mild diarrhoea: Looser stools or a change in bowel habits.
• Joint or muscle aches: Discomfort that may affect daily activities.
• Reduced appetite or mild nausea: Changes in appetite or stomach comfort.
• Flu-like symptoms: Chills or a low fever, sometimes following an infusion.

Some symptoms improve with simple measures or prescribed medicines. Even mild symptoms should be reported to your cancer care team, because they may be an early sign of inflammation that needs assessment.

Warning Signs That Need Urgent Attention

Do not wait for your next scheduled appointment if you develop concerning symptoms during immunotherapy. Contact your cancer care team promptly or seek emergency care, depending on the severity, if you notice:

• Diarrhoea or abdominal pain: Frequent or watery diarrhoea, blood or mucus in the stool, or severe abdominal pain.
• Breathing or chest symptoms: New cough, breathlessness or chest pain, which may indicate lung inflammation called pneumonitis.
• Possible liver problems: Yellowing of the skin or eyes, dark urine or pain in the upper right abdomen.
• Neurological or hormonal symptoms: Severe headache, confusion, vision changes or extreme weakness.
• Possible high blood sugar: Excessive thirst, frequent urination or sudden unexplained weight loss.
• Severe skin reactions: A widespread rash, blistering or sores in the mouth.
• Possible heart involvement: Chest pain, palpitations or new muscle weakness.
• Fever: A fever during cancer treatment should be reported promptly, particularly when accompanied by other symptoms.

Severe immune-related reactions are less common but can progress quickly. Treatment may involve pausing immunotherapy and using medicines, such as corticosteroids, to control inflammation. The right treatment depends on the suspected reaction and its severity.

Long-Term Side Effects of Immunotherapy

Some side effects do not fully settle after treatment ends. Long-term effects can include hormone-related problems involving the thyroid, adrenal glands or pituitary gland. When a gland is permanently affected, ongoing hormone replacement may be necessary.

A 2026 study reported in JAMA Network Open, involving 303 people treated with immunotherapy after melanoma surgery, found that 48% developed a chronic immune-related side effect. Underactive thyroid function, joint pain and skin symptoms were among the reported problems. These findings may not apply equally to people with other cancers or receiving different treatments, but they highlight the importance of follow-up.

Other persistent effects may include joint pain, dry mouth, dry eyes or skin changes. Their duration and severity vary, and management depends on the specific condition.

How Your Care Team Monitors Side Effects

Before and during treatment, your team may ask about new symptoms and arrange blood tests to monitor thyroid function, liver and kidney function, blood sugar and other measures relevant to your treatment.

You can help by:

• Keeping a simple diary of new symptoms and when they began.
• Reporting changes early instead of waiting for your next appointment.
• Carrying a treatment card or note stating that you receive immunotherapy.
• Checking with your care team before starting new medicines or supplements.
• Informing other healthcare professionals about your immunotherapy, even after treatment has ended.

Knowing When to Seek Help During Immunotherapy

Immunotherapy side effects occur because the immune system becomes more active, and they can affect almost any part of the body. Many are manageable, but symptoms such as severe diarrhoea, breathlessness, jaundice, confusion or chest pain require urgent medical assessment. Some effects, especially hormone-related problems, may be long lasting and need ongoing treatment.

Reporting changes early can help your care team identify and manage complications. Regular follow-up remains important even after treatment finishes.

The medical oncology department at AS LifeLine Cancer Care Hospital, Delhi, provides immunotherapy alongside monitoring and management of treatment-related side effects.

Frequently Asked Questions

Do side effects mean the treatment is working?

Not necessarily. Some studies suggest a possible association between certain immune-related side effects and treatment response, but many people respond to immunotherapy without experiencing side effects. Symptoms alone cannot show whether treatment is working.

Will I need to stop immunotherapy if I get side effects?

Mild side effects may not require stopping treatment. More serious reactions may require a temporary pause, treatment for the inflammation or a change in the treatment plan. Your oncologist will advise based on the symptoms and their severity.

Can side effects start after treatment ends?

Yes. Some immunotherapy side effects can appear or persist months after treatment ends. Tell your healthcare team about your previous immunotherapy if you develop new symptoms.