The short answer
Infusion reactions most often happen in the first minutes to hours of a drip. Nurses pause the infusion and give medicines. Whether the same drug can be given again is your treatment team's decision.
Most infusion reactions happen during the first few minutes to hours of an infusion, but some show up days or even weeks later.
Common symptoms include itching, flushing, rash or hives, chest discomfort, shortness of breath, nausea and dizziness.
Tell the nurse the moment anything feels different.
The nurse may pause the infusion, check vital signs and give medicines to relieve symptoms.
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What an infusion reaction is
The American Cancer Society describes infusion reactions as symptoms or side effects that can happen if your immune system overreacts to cancer treatment given through an IV. It is not a sign that you did anything wrong.
Nurses watch you for signs of a reaction and check your vital signs. The infusion may start slowly and speed up if no reaction occurs.
What it can feel like
Common symptoms listed by the American Cancer Society include:
- itching
- redness (flushing) on the face and neck
- rash or hives
- chest discomfort
- shortness of breath
- nausea
- dizziness
Anything that feels new or wrong during an infusion is worth saying out loud. Do not wait to see whether it passes.
When reactions usually happen
Most reactions happen during the first few minutes to hours of an infusion. The American Cancer Society calls this an immediate reaction. Some reactions show up days or even weeks after treatment. Ask your team which pattern applies to your drug.
What your team does
Your nurse may pause the infusion and check your vital signs. Then you are given medicines to relieve the symptoms. Some people get premedication before the infusion, usually antihistamines, steroids or fever-reducing medicines, when the treatment is more likely to cause a reaction.
Anaphylaxis is a rare, severe reaction. It is treated with epinephrine, and infusion nurses are trained to give it.
Going back for the next dose
Feeling anxious before the next infusion after a reaction is common. Ask what will be different next time. Ask about premedication, infusion speed, how long you will be watched, and the plan if symptoms return. Whether the same drug can be given again is your treatment team's decision.
When to get help sooner
- Call 911 or go to an emergency department right away if you have trouble breathing, wheezing, trouble swallowing, swelling of the face or tongue, hives spreading over the body, chest discomfort, dizziness or feeling faint after you have left the infusion suite. MedlinePlus says anaphylaxis symptoms often develop within seconds or minutes, and to call 911 or the local emergency number immediately. Do not drive yourself.
- Press the call button in the chair straight away if any symptom begins while the drip is running. Say what you feel. Your nurse can pause the infusion.
- Call your care team right away, day or night, if you have a temperature of 100.4 F (38 C) or higher (NCI uses 100.5 F) after chemotherapy. CDC says to call your doctor immediately, and to tell emergency staff you are a cancer patient on chemotherapy. See fever during chemotherapy.
- Call your cancer team right away if you have any symptoms of a reaction at home after your infusion, such as a rash, itching, flushing or feeling unwell. The American Cancer Society says to call right away.
Sources
- American Cancer Society: Infusion and Immune Reactions
- MedlinePlus: Anaphylaxis
- CDC: Fever and cancer treatment
Common questions
Does having a reaction mean I can never have this drug again?
Not always. Whether the drug can be given again, and with what precautions, is your treatment team's decision.
I felt fine for several infusions. Can a reaction still happen?
Possibly. Tell the nurse about new sensations at any infusion. Some reactions also appear days or weeks after treatment.
What is premedication and will I need it?
Premedication is medicine given before the infusion, usually antihistamines, steroids or fever-reducing medicines, for treatments with a higher chance of a reaction. Ask your team whether you need it.
Questions to ask your doctor
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Get urgent help
Fever of 100.4°F (38°C) or higher during chemo, severe pain, or trouble breathing: call your cancer care team right away, day or night. Call 911 for an emergency.
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Written by: Cancer ExplainedSources last checked: 2026-10-02 what this meansLast updated: 2026-10-02Next planned review: 2027-01-30
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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