# What are the side effects of immunotherapy?

Source: https://oncologyistanbul.com/answers/side-effects-of-immunotherapy
Last updated: 2026-07-13

Because immunotherapy revs up the immune system, it may cause side effects — including immune-related ones, where the boosted immune system also acts against healthy cells and organs and causes inflammation. Per the National Cancer Institute (NCI), effects can include flu-like symptoms (fever, chills, fatigue, weakness, nausea, muscle or joint aches, headache), injection-site skin reactions (redness, rash, itching, swelling), diarrhea, infection, and organ inflammation. Which effects occur varies by person, cancer type, and the drug and dose, and they can happen during or after treatment — so ask your doctors and nurses what signs to watch for. This is general information, not personal medical advice.

## Verify at
- [Immunotherapy to Treat Cancer — Side Effects](https://www.cancer.gov/about-cancer/treatment/types/immunotherapy/side-effects) — National Cancer Institute (NCI) (checked 2026-07-13)
- [Immunotherapy to Treat Cancer](https://www.cancer.gov/about-cancer/treatment/types/immunotherapy) — National Cancer Institute (NCI) (checked 2026-07-12)

Related: [Immunotherapy, in depth](https://oncologyistanbul.com/treatments/immunotherapy)