Immunity and infection prevention

Food safety

When the immune system is weak, germs carried by food — such as Listeria, Salmonella or Campylobacter — can cause more serious illness than in healthy people. The good news is that simple kitchen rules lower the risk considerably. This topic covers the four steps of safe food, which foods to avoid and what current evidence says about the “neutropenic diet”.

Last updated: 30 September 2026~7 min read

A softly lit clean kitchen counter on a dark navy background: two separate chopping boards, fresh vegetables and softly glowing water droplets; no people. — **Figure 1.**Concept: a safe kitchen — clean hands, separate boards, thorough cooking and proper chilling.

01Short answer

Food safety rests on four steps: clean (hands, surfaces, utensils), separate (keep raw meat and seafood away from ready-to-eat food), cook (cook meat, poultry, fish and eggs thoroughly) and chill (put perishable food in the fridge within two hours and keep the fridge at 4 °C or below). When your immune system is weak, it is advised to avoid raw and undercooked meat and fish (including sushi), raw eggs or eggs with runny yolks, unpasteurised milk and cheese or yogurt made from it, raw sprouts, deli meats that have not been reheated, and unwashed fruit and vegetables. Make sure your water is safe too. Studies have shown that a very strict “neutropenic diet” does not reduce infections; what matters is safe food handling. Rules may be stricter after a transplant — your hematology team and dietitian set the rules for you.

02Simple explanation

Food is a source of strength and sometimes a “vehicle” for germs. In a healthy person, food poisoning usually means a few days of diarrhea and vomiting. When the immune system is weak, these germs can get into the blood and cause a serious infection.

WHO recommends five simple keys to safer food: keep clean, separate raw and cooked, cook thoroughly, keep food at safe temperatures and use safe water and raw materials. These rules help everyone, and they matter especially for people on treatment.

Some foods are riskier because they are eaten raw or because germs can grow in them even in the fridge. Listeria, for example, survives the cold and can be found in unpasteurised dairy products, deli meats and smoked fish. It is safer either to heat such foods thoroughly or to leave them off the menu for a while.

Some traditional home-made foods — such as cheese, yogurt or ayran made from unboiled milk — are not pasteurised and can carry a risk. Products made from boiled or pasteurised milk are safer. Cook kebabs and other meat dishes until they are done all the way through.

Food is also pleasure and a bond with family. The goal is not to be afraid but to make sensible choices. You can keep eating most of your favourite dishes if they are prepared properly.

03Scientific explanation

The main germs: Listeria monocytogenes (unpasteurised milk and soft cheeses, deli meats, refrigerated smoked fish, raw sprouts), Salmonella (raw eggs, poultry), Campylobacter (undercooked chicken), Shiga toxin-producing E. coli (undercooked minced meat, unpasteurised juices), norovirus and hepatitis A (contaminated produce), and Toxoplasma (undercooked meat). Because Listeria can grow at fridge temperatures, it matters especially for people with weak immunity and can cause bloodstream infection or meningitis.

Safe internal temperatures (measured with a food thermometer): all poultry and reheated leftovers — 74 °C; minced meat and egg dishes — 71 °C; whole cuts of beef, lamb and pork, and fish — 63 °C (with a three-minute rest for whole cuts). The fridge should be ≤4 °C and the freezer ≤−18 °C. Perishable food should not stay at room temperature for more than two hours, or more than one hour when the air temperature is above 32 °C.

Evidence on the “neutropenic diet”: traditionally, a strict diet banning all raw fruit and vegetables was used during neutropenia. A randomised trial in patients receiving induction treatment for AML (JCO, 2008) found no significant difference in infections between a cooked-only diet and a diet that allowed raw foods. A later systematic review and meta-analysis (2019) also showed that the neutropenic diet did not reduce infections. That is why many centres now recommend safe food handling rules instead of strict bans.

Individual differences: after an allogeneic transplant, with graft-versus-host disease or with very deep, prolonged neutropenia, centres may apply stricter rules (for example, avoiding restaurant food or buffets for a while). Food choices also change with mucositis, nausea and poor appetite. Herbal teas, supplements and “health” drinks can be a source of germs and can also interact with medicines; agree them with your team.

04What happens in the body?

When should you seek urgent help?

Call your hematology team straight away if: your temperature is 38 °C or higher; you have watery diarrhea 4 or more times in 24 hours; vomiting stops you keeping fluids or medicines down; there is blood in your stool; you have severe abdominal pain or signs of dehydration (dry mouth, little urine, dizziness); you develop a stiff neck, a severe headache or confusion.

The four steps of safe food

Clean: wash your hands before preparing food and after touching raw meat; wash boards, knives and surfaces with hot soapy water. Separate: use a separate board for raw meat, poultry and fish, and store them on the bottom shelf of the fridge in closed containers. Cook: cook meat until it is done all the way through, using a food thermometer if you can. Chill: put leftovers in the fridge within two hours and use them within a day or two; thaw frozen food in the fridge.

Which foods should you avoid?

Raw or undercooked meat, poultry and minced meat (such as rare steak or undercooked kebab); raw or undercooked fish and seafood (sushi, raw oysters); raw eggs or eggs with runny yolks, and sauces made with them; unpasteurised milk, cheese, yogurt, ayran and juices; raw sprouts; deli meats and sausages that have not been reheated; refrigerated smoked fish; unwashed fruit and vegetables; open buffets, street food, and food that has been left out at room temperature for a long time.

A frying pan glowing warm gold on a dark background with soft steam above it; soft teal backlight, no text or numbers. — **Figure 2.**Proper cooking kills germs: meat should be cooked all the way through.

Safer alternatives

Thoroughly cooked meat and poultry; thoroughly cooked fish; hard-boiled eggs; pasteurised milk and cheese or yogurt made from it; deli meats heated until steaming; cooked sprouts; well-washed or peeled fruit and vegetables; packaged pasteurised juices. Check use-by dates and that packaging is intact.

Water and drinks

If you are not sure about the quality of your tap water, drink boiled or sealed bottled water. Make sure ice is made from safe water too. Do not drink untested well or spring water. Avoid unpasteurised juices and drinks such as home-made kvass. Discuss herbal teas and “immune” drinks with your team.

Cool teal light from an open fridge; neat closed containers arranged on the shelves, dark navy background. — **Figure 3.**The cold chain: perishable food should go into the fridge in good time.

Questions for your doctor or dietitian

Do I need a special diet, or are safe food rules enough? Can I eat raw fruit and vegetables? Can I eat in restaurants, and when? What about home-made cheese and yogurt? Is tap water safe for me? Which supplements and herbal teas should I avoid? What should I do when I have no appetite?

05From shop to plate: the safe route

Food safety starts with shopping and ends at the table.

1ShoppingCheck use-by dates and packaging; pick up chilled items last.

2StorageFridge at 4 °C or below; raw meat on the bottom shelf in a closed container.

3PreparationClean hands, separate boards, washed produce.

4CookingUntil done all the way through; reheat leftovers until steaming.

Less riskSimple rules greatly reduce food-borne infections.

Together with familyEveryone should know the kitchen rules.

If signs appearCall straight away with a fever or severe diarrhea.

06Risky foods and safer alternatives

Food group	Advised to avoid	Safer choice
Meat and poultry	Raw, undercooked or rare meat; undercooked kebab	Meat cooked all the way through (poultry 74 °C, minced meat 71 °C)
Fish and seafood	Sushi, raw oysters, refrigerated smoked fish	Thoroughly cooked fish; canned fish
Eggs	Raw eggs or runny yolks, sauces with raw egg	Eggs cooked until yolk and white are firm
Dairy	Unpasteurised milk; home-made cheese, yogurt or ayran from raw milk	Products made from pasteurised or boiled milk
Fruit and vegetables	Unwashed produce, raw sprouts, bruised or rotten parts	Produce washed well under running water or peeled; cooked sprouts
Deli meats	Cold sausage, hot dogs, pate	Products heated until steaming
Water and drinks	Untested well water, unpasteurised juices	Boiled or bottled water; pasteurised juices

* This table is general information. Rules may be stricter after a transplant or in special situations — your hematology team and dietitian will tell you.

07Key terms

Food poisoning: Illness caused by food contaminated with a germ or its toxin.
Listeria: A bacterium that can grow in the cold; dangerous when immunity is weak.
Salmonella: A bacterium that can spread through raw eggs and poultry.
Pasteurisation: Heating milk and juices to kill germs.
Cross-contamination: The transfer of germs from raw food to ready-to-eat food, hands or surfaces.
Internal temperature: The temperature of the thickest part of a food, measured with a thermometer.
Neutropenic diet: A strict diet limiting raw foods during neutropenia; its benefit has not been proven.
Danger zone: About 5–60 °C; germs multiply quickly in this range.
Dietitian: A nutrition specialist who helps build a personal eating plan.
Toxoplasma: A parasite spread through undercooked meat and cat faeces.

08Key points

Four steps: clean, separate, cook, chill.
Cook meat, poultry, fish and eggs thoroughly.
Avoid unpasteurised dairy products.
Heat deli meats and sausages until steaming.
Wash fruit and vegetables well under running water.
Refrigerate leftovers within two hours.
A strict neutropenic diet has not been shown to help.
Your team and dietitian set your personal rules.

09Frequently asked questions

Can I eat raw fruit and vegetables?

Many centres allow well-washed or peeled fruit and vegetables, because strict bans have not been shown to help. But rules may differ after a transplant or during very deep neutropenia. Ask your team.

Can I eat in restaurants?

Often yes, with care: choose freshly cooked hot dishes, avoid buffets, salad bars and street food, and ask for meat to be well done. After a transplant you may be advised to avoid restaurants for a while.

Can I eat home-made yogurt and cheese?

If they are made from boiled or pasteurised milk in clean conditions, the risk is lower. It is safer to avoid cheese and yogurt made from raw milk during treatment.

Can I take probiotics?

Probiotics are live germs, and in people with very weak immunity they can rarely get into the blood and cause infection. Talk to your team before taking probiotic supplements.

Can I eat honey?

Pasteurised, packaged honey is usually considered safe. Some centres advise avoiding unprocessed raw honey during treatment. Follow your team’s rules.

Worrying about food is spoiling my appetite. What can I do?

Nutrition matters a great deal during treatment. Focus on safe favourite foods rather than on a list of bans. Talking to a dietitian, small portions and safe versions of the dishes you love can help.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

Which foods should I avoid with my current blood counts?
Can I eat raw fruit and vegetables, and how should I wash them?
Is food brought from outside safe?
Until when should I follow these food rules?

My questions

12Sources

World Health Organization (WHO). Five keys to safer food manual
World Health Organization (WHO). Food safety — fact sheet
Centers for Disease Control and Prevention (CDC). Safer Food Choices for People With Weakened Immune Systems
Centers for Disease Control and Prevention (CDC). Foods That Can Cause Food Poisoning
Centers for Disease Control and Prevention (CDC). Preventing Listeria Infection
FoodSafety.gov (U.S. Department of Health and Human Services). People at Risk: Those with Weakened Immune Systems
FoodSafety.gov (U.S. Department of Health and Human Services). Cook to a Safe Minimum Internal Temperature
U.S. Food and Drug Administration (FDA). Food Safety for Older Adults and People with Cancer, Diabetes, HIV/AIDS, Organ Transplants, and Autoimmune Diseases
Journal of Clinical Oncology, 2008. Randomized Comparison of Cooked and Noncooked Diets in Patients Undergoing Remission Induction Therapy for Acute Myeloid Leukemia
BMJ Supportive & Palliative Care, 2019. Neutropenic diets to prevent cancer infections: updated systematic review and meta-analysis
Memorial Sloan Kettering Cancer Center. Food Safety During Cancer Treatment
American Cancer Society. Preventing Infections in People with Cancer
Blood Cancer UK. Preventing infection

Medical disclaimerThis information is for educational purposes only and does not replace medical advice.

Last updated: 30 September 2026← Back to the list

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