Key points
- Many side effects of immunotherapy happen when the immune system, boosted against the cancer, also attacks healthy cells and tissues [1].
- The commonest side effects of immune checkpoint inhibitors are skin rash, diarrhoea and tiredness; inflammation of organs such as the bowel, liver, lungs, thyroid, pituitary gland, kidneys and heart is less common but important [2].
- Side effects can happen at any time during treatment and even after it ends [1, 5].
- Most side effects can be controlled by pausing the drug and giving corticosteroids if they are found early; with severe side effects the drug is usually stopped [3].
- Fatal side effects are rare: in a review of more than 100 studies, fewer than one in 100 patients died because of a side effect; slightly more with a combination of two immunotherapy drugs [6].
- Report any new symptom (diarrhoea, cough, breathlessness, chest pain, yellowing of the skin, severe headache, muscle weakness) straight away, and tell every doctor you see that you are having immunotherapy [1, 2, 3].
Why does immunotherapy cause side effects?
"Checkpoints" are a normal part of the immune system and stop it overreacting against healthy cells. Some tumours use these same brakes (such as the proteins PD-1, PD-L1 and CTLA-4) to hide from T cells. Checkpoint inhibitors release these brakes so that T cells can destroy the cancer [2]. But releasing the brakes can make the immune system attack healthy organs too; these side effects are called immune-related adverse events (irAEs) [1, 5].
These drugs are approved for many types of cancer, including lung cancer, melanoma, kidney, bladder, head and neck, breast, stomach, liver and cervical cancer, and Hodgkin lymphoma [2]. The type and severity of side effects depend on your health before treatment, the type and stage of cancer, and the type and dose of immunotherapy [1]. The risk of thyroid problems and inflammation of the pituitary gland is higher with a combination of two inhibitors (PD-1 and CTLA-4) [7].
| Symptoms to report | Possible side effect (organ) |
|---|---|
| Rash, itching, changes in skin colour [2] | Dermatitis (skin) |
| Diarrhoea, tummy pain, blood or mucus in the stool [2] | Colitis (bowel) |
| Yellow skin or eyes, dark urine, pain on the right side of the tummy; often seen only on a blood test [2] | Hepatitis (liver) |
| A new cough, breathlessness, chest pain [2] | Pneumonitis (lungs) |
| Severe tiredness, weight change, a racing heart, headache, thirst and passing a lot of urine [2, 7] | Underactive or overactive thyroid, inflammation of the pituitary gland, diabetes (hormone glands) |
| Passing less urine, swelling; often seen on a blood test [2] | Nephritis (kidneys) |
| Chest pain, a racing heart, breathlessness; rare but with the highest death rate [6] | Myocarditis (heart) |
| Muscle weakness, numbness, difficulty breathing [2] | Nerve and muscle side effects (nerves) |
With CAR-T cell therapy, a side effect called cytokine release syndrome can happen: a large amount of cytokines is released into the blood, causing fever, nausea, headache, rash, a racing heart, low blood pressure and difficulty breathing. Most cases are mild, but in some people it is severe or life-threatening [8]. Nerve side effects can also happen, and doctors use the ASTCT consensus criteria to grade these two side effects [9]. Patients are watched closely after a CAR-T infusion.
What helps?
Your part in staying safe
- 1
- 2
Report early
Do not wait for symptoms to "get better on their own". Most side effects can be controlled if treated early, and sometimes immunotherapy can continue [3].
- 3
Do not treat yourself
Do not take medicines for diarrhoea or a rash without talking to your care team; diarrhoea may be a sign of colitis and needs to be checked [3].
- 4
Regular tests
Have your regular blood tests (such as liver enzymes, thyroid, blood sugar and creatinine); some side effects only show up on tests [4].
- 5
- 6
Take steroids exactly as prescribed
If you are given a corticosteroid (such as prednisolone) for a side effect, do not stop it on your own; it is usually reduced gradually over at least 4 to 6 weeks [3].
| Common belief | Fact |
|---|---|
| Immunotherapy has no side effects because it is "natural". | Immunotherapy can cause inflammatory side effects in any organ, which are sometimes severe [1, 2]. |
| Taking steroids for a side effect cancels out the immunotherapy. | Corticosteroids are a standard part of treating moderate to severe side effects in the guidelines, and treating a side effect in time is vital [3]; the decision about continuing immunotherapy rests with your oncologist. |
What can your doctor do?
Show detailsHide
| Severity | Usual approach |
|---|---|
| Grade 1 (mild) | Continue immunotherapy with close monitoring; except for some nerve, blood and heart side effects [3] |
| Grade 2 (moderate) | Pause immunotherapy in most cases and consider restarting once back to grade 1 or less; corticosteroids may be given [3] |
| Grade 3 (severe) | Usually stop immunotherapy and start high-dose corticosteroids; reduce gradually over at least 4 to 6 weeks [3] |
| Grade 4 (life-threatening) | Usually stop immunotherapy permanently, except hormone gland side effects controlled with hormone replacement [3] |
Some cases that do not respond to corticosteroids need other immunosuppressive medicines [3]. The exact decision depends on the organ involved.
For physicians
Guideline summary for physicians
- ASCO 2021 (175 studies; recommendations mostly based on expert consensus): the general approach by grade is summarised in the table above, and organ-specific recommendations are in the full guideline [3].
- ESMO 2022: a comprehensive guideline on the diagnosis, treatment and follow-up of immunotherapy toxicities by organ, including baseline assessment before treatment and management of steroid-refractory cases [4].
- Fatal toxicities (Wang and colleagues): of 613 deaths reported to the WHO database, anti-CTLA-4 deaths were mostly from colitis (70%), and anti-PD-1/PD-L1 deaths mostly from pneumonitis (35%), hepatitis (22%) and neurotoxicity (15%); with combination treatment, colitis (37%) and myocarditis (25%). Myocarditis had the highest fatality (39.7% of 131 cases). Deaths were early (median 14.5 days with combination treatment and 40 days with anti-PD-1 and ipilimumab). Toxic death rates in the meta-analysis: 0.36% anti-PD-1, 0.38% anti-PD-L1, 1.08% anti-CTLA-4 and 1.23% combination [6].
- Endocrinopathies (meta-analysis of 38 trials, 7551 patients): the risk of hypothyroidism (OR 3.81) and hyperthyroidism (OR 4.27) was higher with combination treatment than with ipilimumab; hypophysitis was lower with PD-1 than with ipilimumab (OR 0.29) and higher with combination treatment (OR 2.2) [7].
When should I call my doctor?
During immunotherapy and for months afterwards, call your care team straight away or go to the emergency department if you have any of these symptoms:
- Diarrhoea or opening your bowels more often than usual, tummy pain, or blood or mucus in the stool [2, 3].
- A new cough, breathlessness or chest pain [2].
- A racing heart, chest pain or sudden breathlessness; myocarditis is rare but dangerous [6].
- Yellowing of the skin or the whites of the eyes, dark urine, nausea or pain on the right side of the tummy [2].
- A severe or lasting headache, changes in vision, severe tiredness, dizziness, thirst and passing a lot of urine [2, 7].
- Muscle weakness, numbness, difficulty swallowing or breathing [2].
- A widespread rash, blisters or mouth sores [2].
- A temperature of 38 °C or higher, especially after CAR-T treatment or if you are having chemotherapy at the same time [8, 10].
Frequently asked questions
When do side effects usually start?
Does immunotherapy cause nausea and hair loss like chemotherapy?
If I get an underactive thyroid, is it permanent?
An underactive thyroid caused by immunotherapy is usually controlled with thyroid hormone tablets, and immunotherapy can usually continue [3]. Your doctor follows your thyroid with regular tests.
Can I have vaccines during immunotherapy?
Go over your vaccinations with your oncologist; the vaccine schedule for people with cancer may depend on the type of treatment [12].
Related cancer types
Related guides
References
12 referencesShow all references, 8 with a study cardClose the reference list
Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
- 1
- 2
- 3
- 4Management of toxicities from immunotherapy: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up
- 5
- 6
- 7
- 8
- 9ASTCT Consensus Grading for Cytokine Release Syndrome and Neurologic Toxicity Associated with Immune Effector Cells
- 10Infection and Neutropenia during Cancer Treatment
- 11Antiemetics: ASCO Guideline Update
- 12Vaccination of Adults With Cancer: ASCO Guideline
This page is based on reputable scientific sources and was last updated on 28 October 2026. The content of this website is for educational and informational purposes only and does not replace consultation, diagnosis or treatment by a specialist physician. Consult your treating physician about any treatment decision.
Printed from the website; the full and up-to-date version: https://drdabiri.com/en/guides/immunotherapy-side-effects/
