When your immune system goes into overdrive trying to fight cancer, it can accidentally start attacking your own organs—that’s what immune-related adverse events, harmful reactions caused by the immune system attacking healthy tissue during immunotherapy are. These aren’t typical side effects like nausea or fatigue. They’re autoimmune reactions, where your body’s defenses turn against your skin, gut, liver, lungs, or even your thyroid. This happens most often with checkpoint inhibitors, a class of cancer drugs that remove brakes from immune cells to help them kill tumors, like pembrolizumab or nivolumab. It’s not rare: up to 1 in 3 people on these drugs will experience some form of immune-related issue, and a few of those can be serious enough to require hospital care.
What makes these reactions tricky is how they mimic other diseases. A rash might look like an allergy, diarrhea could be mistaken for an infection, and fatigue might just be blamed on cancer itself. But if you’re on immunotherapy and suddenly develop joint pain, yellow eyes, or trouble breathing, it’s not just "feeling off"—it’s your immune system signaling trouble. That’s why doctors monitor blood tests, ask detailed questions, and sometimes do biopsies to confirm it’s an autoimmune reaction, a condition where the immune system mistakenly targets the body’s own cells and not something else. The good news? Most of these reactions can be controlled with steroids or by pausing treatment, if caught early. The bad news? If ignored, they can lead to permanent organ damage or even death.
These events don’t just happen with cancer drugs. They’ve also shown up with newer treatments for autoimmune diseases, and even in some vaccines, though much less often. The key takeaway? If you’re getting a treatment that boosts your immune system, you need to know the warning signs. You’re not just tracking tumor shrinkage—you’re also watching for changes in your skin, digestion, energy, or breathing. The posts below cover real cases, from mild rashes to life-threatening colitis, and show how doctors and patients navigate these risks without giving up on life-saving therapies. You’ll find practical advice on spotting early symptoms, what tests matter, and how to talk to your care team when something feels wrong.
Learn how to recognize and manage immune-related adverse events (irAEs) caused by cancer immunotherapy. Understand symptoms, grading, treatment with steroids and other drugs, and why early action saves lives.