Why does food safety matter during cancer treatment?

Some cancer treatments weaken your immune system, which makes it harder to fight infections—including illness from contaminated food. Food poisoning is a bigger risk when your immune system is weak.

What is happening in your body

The National Cancer Institute (NCI) says chemotherapy can reduce the number of your white blood cells, which fight infection, and that this raises the risk of infection, including from food. NCI says the same for people having a stem cell transplant, because the treatment before the transplant lowers white blood cell counts.

CDC says your doctor or nurse will let you know when your white blood cell count is likely to be at its lowest, and that you should watch carefully for signs of infection during that time. Ask your team when that is for you.

The number that means call now

CDC says fever may be the only sign of an infection during chemotherapy, and that an infection can be life-threatening.

Call your care team immediately for a temperature of 100.4°F (38°C) or higher. CDC says to call right away even if it happens in the middle of the night, and calls it an emergency. If you cannot reach your team, or you have trouble breathing or feel very unwell, go to the emergency department or call 911. NCI says to talk with your doctor or nurse before taking any medicine for a fever, even acetaminophen, because it can lower a fever but may hide signs of a more serious problem.

Which foods carry the most risk

CDC lists specific higher-risk foods for people with weakened immune systems:

• Unheated deli meat, cold cuts, hot dogs, and dry or fermented sausages
• Soft cheeses made from unpasteurized milk, queso fresco varieties, and unheated deli-sliced cheese
• Raw or undercooked sprouts
• Unpasteurized milk and anything made from it, and unpasteurized juice or cider
• Raw or undercooked eggs, and raw dough or batter
• Sushi, sashimi, ceviche, and other raw or undercooked fish or shellfish
• Cut melon left out more than 2 hours, or 1 hour above 90°F

Deli meat is not banned outright. CDC's safer choice is deli meat, cold cuts, hot dogs, and dry or fermented sausages heated to 165°F or until steaming hot.

Temperatures worth memorizing

Bacteria multiply fastest between 40°F and 140°F, the range CDC calls the danger zone. Keeping food out of it is most of the job.

A food thermometer beats color or texture every time. Cook all poultry, including ground chicken and turkey, to 165°F. Cook ground beef and pork to 160°F. Cook whole cuts of beef, veal, lamb, and pork to 145°F, then let them rest 3 minutes. Fish is done at 145°F, or when the flesh turns opaque and flakes apart.

Practical habits

Scrub raw fruit and vegetables under running water, even ones you plan to peel. The knife drags germs from the rind into the flesh. Keep separate cutting boards and utensils for raw meat and produce. Chill leftovers within 2 hours, or within 1 hour if the room is above 90°F.

If a stem cell transplant is part of your plan, expect stricter rules for a while afterward. Your transplant team will give you their own list. It takes priority over general advice.