Immune-Related Adverse Events: What They Are and Which Drugs Cause Them

When your immune system goes too far, it doesn’t just fight infections—it starts attacking your own organs. These are called immune-related adverse events, harmful reactions caused when drugs accidentally turn the immune system against healthy tissues. Also known as irAEs, they’re most common with immunotherapy, cancer treatments that boost the body’s natural defenses, but can also happen with other drugs like checkpoint inhibitors, a class of drugs that remove brakes on immune cells. Unlike typical drug side effects, these aren’t just nausea or dizziness—they can cause colitis, hepatitis, lung inflammation, or even diabetes.

These reactions don’t show up right away. You might feel fine for weeks or months after starting treatment, then suddenly develop diarrhea, skin rashes, joint pain, or trouble breathing. That’s why doctors monitor you closely during and after treatment. Some patients mistake these symptoms for a cold or allergy, but if you’re on immunotherapy or certain biologics, any new symptom needs attention. The most common triggers include drugs like pembrolizumab, nivolumab, and ipilimumab—used for melanoma, lung cancer, and kidney cancer—but even older drugs like interferons or TNF blockers can cause similar issues. It’s not just cancer patients either. People taking biologics for rheumatoid arthritis or psoriasis can develop immune-related problems too. The key is recognizing the pattern: if a new symptom appears after starting a drug that affects immunity, it’s not random—it’s likely related.

What makes these reactions tricky is that stopping the drug doesn’t always fix things. Sometimes you need steroids, sometimes immunosuppressants, and in rare cases, hospitalization. The good news? Most cases are manageable if caught early. That’s why knowing the warning signs matters more than you think. You’re not just tracking side effects—you’re protecting your organs. Below, you’ll find real cases and drug-specific risks from trusted sources, covering everything from lung inflammation to thyroid damage. No fluff. Just what you need to spot, when to act, and which medications are most likely to trigger these hidden dangers.