When your immune system goes after cancer, it can sometimes turn on your own body. These unintended attacks are called irAEs, immune-related adverse events that occur as a side effect of immunotherapy drugs. Also known as immune-mediated adverse reactions, they’re not allergic responses—they’re the result of overactive immune cells attacking healthy tissue. This happens most often with checkpoint inhibitors, drugs like Keytruda and Opdivo that remove the brakes on immune cells to help them fight tumors. While these drugs have changed how we treat cancers like melanoma and lung cancer, they come with a trade-off: your immune system might start attacking your skin, gut, liver, or even your thyroid.
irAEs aren’t rare. About 1 in 3 people on immunotherapy will have at least one. Some are mild—like a rash or tiredness—but others can be life-threatening if missed. Colitis, inflammation of the colon that causes severe diarrhea and cramping is one of the most common and dangerous. Hepatitis, liver inflammation that raises liver enzymes shows up in blood tests before symptoms appear. And thyroid dysfunction, either underactive or overactive thyroid from immune attack can be mistaken for regular fatigue or stress. The key is catching them early. Doctors now check blood work and ask specific questions at every visit—not just about cancer, but about new rashes, stomach pain, or breathing changes.
There’s no one-size-fits-all fix. Mild irAEs might just need a steroid pill. Severe ones require stopping immunotherapy and using high-dose IV steroids. Some patients never get back on treatment. Others do, with close monitoring. What’s clear is that ignoring symptoms doesn’t make them go away—it makes them worse. The posts below cover real cases: how a skin rash turned into a full-body reaction, why a patient’s fatigue wasn’t just cancer-related, and how doctors learned to spot liver damage before it became critical. You’ll find practical advice on what to watch for, how to talk to your care team, and what treatments actually help without risking more harm.
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.