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Watching for and Preventing Infections

Cancer and cancer treatments can weaken the immune system. The immune system is a complex system the body uses to resist infections by germs, such as bacteria or viruses.

When the immune system is weakened, there is a higher risk for infection. Because of this, infection is a common complication of cancer and cancer treatment, and certain types can be life-threatening if not found and treated early.

If you're getting treatment for cancer, your cancer care team will talk to you about any increased risk for infection you may have, and what can be done to help prevent infection. Usually the risk is temporary because the immune system recovers after a period of time, but each person is different.

For cancer patients who finished treatment a few years ago or longer, their immune systems have most likely recovered. But this depends a lot on the type of cancer you had, the type of treatment you received, and other medical problems you might have that can affect your immune system.

Different cancer treatments can affect people in different ways. Each patient's immune system responds to, and recovers from, treatment differently. The US Centers for Disease Control and Prevention (CDC) provides guidance for cancer patients, caregivers, and their health care teams about how to prevent infection. Patients with cancer, those in active treatment, and those who have finished any type of treatment may need to take special precautions to prevent infections from viruses and bacteria. They can look at the CDC information and talk to their cancer care team to find out if special precautions are needed, such as if they need to limit or avoid social activities or wear any protective equipment (masks, gloves, etc.).

If you are getting any type of treatment for cancer or previously had cancer that was treated with surgery, radiation therapy, chemotherapy, targeted therapy, immunotherapy, hormone therapy, stem cell or bone marrow transplant, or have used any other types of treatments, it is best to discuss your risk of getting an infection with a doctor who understands your situation and medical history.

Preventing infections in people with cancer

Here are some things you can do that might help prevent infection and illness when your immune system is weak due to cancer and/or cancer treatment:

  • Wash your hands often with soap and warm water. Be sure to wash your hands before eating and before touching your face or mucous membranes (eyes, nose, mouth, etc.).
  • Wash your hands after using the bathroom, blowing your nose, coughing, or sneezing.
  • Wash your hands after touching animals, collecting trash, or taking out garbage.
  • Wash your hands after visiting a public place or touching items used by others.
  • Carry an alcohol-based hand sanitizer to clean your hands when you’re out.
  • Use moist cleaning wipes to clean surfaces and things that you touch, such as door handles, ATM or credit card keypads, and any items that are used by other people.
  • Avoid large crowds of people such as at schools, travel, shopping, social events, and public gatherings. If you have to be around a crowd, it's a good idea to wear a mask.
  • Stay away from anyone with a fever, the flu, or other infection.
  • Get your flu shot every fall. Encourage other members of your household to get it, too. DO NOT get the nasal mist flu vaccine. Ask your doctor if you should get any other vaccinations, such as the pneumococcal vaccine to prevent pneumonia, or the hepatitis B vaccine.
  • If your cancer care team has told you that you have a weakened immune system and that you are at high risk for infection, you might be advised to stay away from children and limit visitors during the respiratory virus season.
  • Bathe every day. Be sure to wash your feet, groin, armpits, and other moist, sweaty areas.
  • After bathing, look for redness, swelling, and/or soreness where any tubes or catheters go into your body.
  • Wear gloves when you garden and wash up afterward.
  • Brush your teeth twice each day using a soft toothbrush. Ask your doctor or nurse if it’s OK to gently floss your teeth or use a water flosser. Tell them if your gums bleed. Your doctor or nurse may give you a special mouthwash to help clean your mouth. Do not use alcohol-based mouthwashes.
  • Keep your groin and anal areas clean. Use soft moist tissues such as disposable baby wipes or bathroom towelettes after using the toilet and anytime you notice irritation or itching. Tell your doctor about any bleeding, redness, or swelling (lumps) in this area.
  • Do not get manicures or pedicures at salons or spas (you can use your own personal and well-cleaned tools at home). Do not use false nails or nail tips.
  • Do not wade, play, or swim in ponds, lakes, rivers, or water parks.
  • Do not get into hot tubs.
  • Wear shoes all the time – in the hospital, outdoors, and at home. This helps you avoid injury and keep germs off your feet.
  • Use an electric shaver instead of a razor to avoid cuts and nicks. Do not share shavers.
  • If you cut or scrape your skin, clean the area right away with soap and warm water. Cover the area with a clean bandage to protect it. If the bandage gets wet or dirty, clean the area and put on a new bandage. Tell your doctor if you notice redness, swelling, pain, or tenderness.
  • Prevent constipation and straining to move your bowels by drinking the recommended amount of fluid each day. Exercising each day can help, too. Ask your doctor how much fluid you should drink daily and if it is safe for you to exercise. Let your doctor or nurse know if you are having bowel problems. If needed, your doctor may give you a bowel softener medicine. Do not put anything in your rectum, including enemas, thermometers, and suppositories.
  • Women should not use tampons, vaginal suppositories, or douche.
  • Use water-based lubricants during sex to avoid injury or abrasion of the skin and mucous membranes. Use latex or plastic condoms to reduce the risk of sexually transmitted infections.
  • Do not keep fresh flowers or live plants in your bedroom.
  • Do not clean up droppings from your pets. Do not clean bird cages, litter boxes, or fish or turtle tanks. Have someone else do this for you.
  • Do not touch soil that may contain feces of animals or people.
  • Do not change diapers, but if you do, wash your hands very well afterward.
  • If you use disposable gloves to avoid touching things like soil or waste, wash your hands after you take off the gloves. (Gloves can have tiny holes that you can’t see.)
  • Stay away from all standing water, for example, in vases, denture cups, and soap dishes. If you store your dentures in a cup, wash the cup and change the water with each use.
  • Use hot water or a dishwasher to clean your dishes.
  • Do not share bath towels or drinking glasses with anyone, including family members.
  • Stay away from chicken coops, caves, and any place where dust from the ground is being blown into the air, such as construction sites.
  • Talk with your doctor or nurse if you are planning any travel during this time.

Be aware of and watch for signs and symptoms of infection. Talk to your doctor about what you should watch for and what you need to report right away.

Food safety tips for the person with cancer

Infections can be picked up from food and drinks. So, food safety is very important when your immune system is weaker than normal. Talk to your cancer care team about whether you need to follow a special diet during your cancer treatment. Wash your hands before handling any food products. Make sure all meat products (this may include chicken, beef, and other meat products) are cooked thoroughly to kill any bacteria that may be present.

Fresh fruits and vegetables can have germs on the outside which can cause illness. Some doctors tell their patients who have weak immune systems not to eat any fresh fruits or vegetables to help lower the risk of infection. Others allow their patients to eat fresh fruits and vegetables as long as they are washed thoroughly first. It’s important to know that even when the outer part of a fruit (such as the peel or rind) isn’t eaten, it still needs to be washed before it’s peeled. If it isn’t, germs can get on the part that is eaten when the peel or rind is cut. It may also be a good idea to avoid certain foods that have been linked to outbreaks before, such as raw vegetable sprouts, fresh salsa, and berries. Be careful eating at salad bars, as they have been sometimes associated with certain bacterial infections.

Talk with your doctor about any dietary questions or concerns you may have, or ask to talk with a registered dietitian. For more detailed information about safely handling foods, see Food Safety During Cancer Treatment

Drugs given to prevent infections during cancer treatment

Sometimes, doctors prescribe medicines when a person’s immune system is very weak – even though there’s no sign of infection. The drugs are given to help keep you from getting an infection.

Preventive drugs

Anti-bacterial, anti-viral, and/or anti-fungal drugs may be used to help prevent infection. You may hear this called prophylactic antibiotic use, or just prophylaxis. Prophylaxis is only used when there’s a very high risk of getting infections (the immune system is very weak). You might also be given antibiotics if you are taking other medicines that can weaken your immune system, such as a long course of steroids or certain chemotherapy drugs.

The preventive drugs are stopped when your immune system is no longer so weak (often some time after the immune-weakening drugs are stopped). Using antibiotics in this way does not prevent all infections. That means it’s still important to use the same precautions as when you aren’t taking preventive drugs, and be sure to tell your doctor about any new signs of infection.

Growth factor drugs

Growth factors are proteins your body makes to help your blood cells grow. They are also known as colony-stimulating factors (CSFs) or myeloid growth factors. Growth factors stimulate the bone marrow to make more white blood cells to help the body fight infection. You can be given injections of man-made CSFs. They are most often used after chemo to help prevent infection. Your doctor also may give you a CSF if your immune system is weak and you have a serious infection that’s getting worse even though you’re getting treatment.

Examples of CSF drugs include filgrastim (Neupogen, other names), pegfilgrastim (Neulasta, other names), tbo-filgrastim (Granix), flapegrastim (Rolvedon), and efbemalenograstim alfa (Ryzneuta).

Growth factors can have side effects in some people, but they can reduce the risk of infection in the patients who need them. Talk to your cancer care team about the risks and benefits of CSFs. Talk to your cancer care team about what side effects you might have while using CSFs and what you can do to manage the side effects.

Watching for infection in cancer patients

Many cancer treatments and cancers can cause changes in your blood counts. A low white blood cell (WBC) count can put you at higher risk of infection.

The WBC count measures your body’s ability to fight infection. There is usually a total WBC count reported in lab results. When your total WBC count is low, you’ll need to watch for signs of infection so that you can get treatment right away. There can also be different types of WBCs reported in lab results underneath the total WBC count. Neutrophils are one of the most important types of WBC counts in a lab report because when they are low, your risk for infection is higher. Monocytes are another type of WBC. A high number of monocytes can mean you have an infection and that your body is helping to fight it by making more monocytes.

Symptoms of infection to look for

  • Fever (a higher than normal body temperature). Your doctor will tell you what temperature to consider a fever. Sometimes, a fever is the only sign of an infection.
  • Any new area of redness, tenderness, or swelling
  • Pus or yellowish discharge from an injury or other location
  • New cough or shortness of breath
  • New abdominal (belly) pain
  • Shaking chills that may be followed by sweating
  • Burning or pain when passing urine
  • Sore throat
  • Sores or white patches in the mouth

What the patient can do

  • Check your temperature by mouth (or under your armpit if you can’t keep a thermometer in your mouth).
  • Keep a working thermometer within easy reach and make sure you and your caregivers know how to use it.
  • Talk to your cancer care team about what to do if you have a fever. Ask if you should take medications like acetaminophen (Tylenol) for a fever.
  • Keep the cancer care team’s contact information with you at all times. Make sure you know when to call, and what number to call during and after regular office hours.
  • If you have to go to the emergency room or urgent care, let the team taking care of you know that you are a cancer patient who recently received cancer treatment.
  • Take antibiotics or other medicine as prescribed.
  • Drink fluids, but don’t force more than you can tolerate.
  • Avoid anything that can cause cuts, scrapes, or other breaks in the skin.​
  • Wash your hands after using the bathroom or visiting public places. Use hand sanitizer when you don’t have soap and water.
  • Avoid crowds, and don’t visit with people who have infections, coughs, or fevers. If you have to be around any of these groups of people, it's a good idea to wear a mask.
  • If you eat raw foods, wash them carefully and peel them to avoid germs.
  • Brush your teeth twice a day. Ask your doctor or nurse if it is safe for you to floss.

What caregivers can do

  • Keep a working thermometer within easy reach and make sure the patient and the caregivers know how to use it.
  • Watch for shaking chills, and check the patient’s temperature after the shaking stops.
  • Check the patient’s temperature using a thermometer in the patient’s mouth or under the armpit. (Do not take a rectal temperature.)
  • Encourage visitors who have diarrhea, fever, cough, or the flu to visit the patient only by phone until they are well.
  • Offer extra fluids.
  • Help the patient take medicines on schedule.
  • Keep the cancer care team's contact information with you at all times. Make sure you know when to call, and what number to call during and after regular office hours.
  • If you have to take the patient to the emergency room or urgent care, let the team there know that this is a cancer patient who recently received treatment.

Call the health care team if the patient

  • Has a fever
  • Has shaking chills
  • Feels or seems “different”
  • Cannot take in fluids

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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Last Revised: December 20, 2023

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