How can I prevent infection during cancer treatment?

Three things: wash your hands often and well, stay extra clean, and avoid germs. Those are the National Cancer Institute's own headings, and the detail underneath each one is what makes them work.

The reason this matters so much is specific. Some cancers and treatments such as chemotherapy lower your white blood cells, the cells that fight infection. During each treatment cycle there are stretches when your neutrophils, a type of white blood cell, are especially low, and your risk is highest then. That state is called neutropenia, and blood tests are how it is tracked.

Hand washing, and everyone else's hands

Use soap and warm water, and wash well, especially before eating. Then do the part people skip: ask the people around you to wash their hands too.

Most infections during treatment come from ordinary contact, not from anything dramatic. A household that all washes properly changes your exposure more than anything you can do alone.

Staying clean where germs get in

If you have a catheter or port, keep the area around it clean and dry. Watch for swelling or redness where it enters your body.

Clean your teeth well, and check your mouth every day for sores or white coating on your tongue. Mouth sores are a common entry point during chemotherapy.

Clean every scrape and cut properly, however small. And tell your doctor or nurse if your bottom is sore or bleeding, since that also raises infection risk.

Avoiding germs, including in food

Stay away from people who are sick or have a cold, and avoid crowds. Avoid people who have just had a live vaccine, such as one for chicken pox, polio, or measles.

Food safety carries more weight than most people expect. The FDA notes that 48 million people in the United States get foodborne infections each year, 128,000 are hospitalized, and 3,000 die, and that people with weakened immune systems are more likely to have a longer illness, be hospitalized, or die from one.

Make sure meat, fish, and eggs are well cooked. Keep hot foods hot and cold foods cold. You may be told to eat only fruits and vegetables you can peel, or to wash all raw produce very thoroughly. Ask your team which version applies to you, because the advice tightens when your counts are lowest.

The fever rule, and a number that does not match

Call your health care team for any sign of infection. NCI is explicit that infections during cancer treatment can be life threatening and require urgent medical attention.

The signs to call about are a fever, chills, cough or sore throat, diarrhea, ear pain, headache or sinus pain, a stiff or sore neck, skin rash, sores or white coating in your mouth or on your tongue, swelling or redness where a catheter enters your body, and urine that is bloody or cloudy or that burns when you pass it.

On the fever threshold, the sources do not quite line up. NCI's infection page, reviewed in January 2020, says a fever of 100.5 °F (38 °C) or higher. But 38 °C actually equals 100.4 °F, and MedlinePlus, reviewed in July 2024, pairs 38 °C with 100.4 °F. The safe reading is to use the lower number, and to ask your own team what threshold they want you to call about.

One more instruction that surprises people: talk with your doctor or nurse before taking aspirin, acetaminophen, or ibuprofen for a fever. Those drugs lower a fever, which can mask the sign of a more serious problem.

Ask which signs mean the emergency room and which mean a phone call. Our guide to infection and neutropenia covers low counts in detail, and the piece on fever during chemotherapy covers what happens when you call.

Sources

• https://www.cancer.gov/about-cancer/treatment/side-effects/infection
• https://medlineplus.gov/ency/article/003090.htm
• https://www.fda.gov/food/people-risk-foodborne-illness/food-safety-older-adults-and-people-cancer-diabetes-hivaids-organ-transplants-and-autoimmune