Why Are People with Cancer More Likely to Get Infections?

People with cancer may have a higher risk of infection because of changes in the immune system that control their body’s defense systems.

Many treatments for cancer can lower your white blood cell counts (causing a condition called neutropenia) and other cells in your immune system. This makes people with cancer more likely to get an infection because their immune system isn’t working as well as it should. Other things that can increase your risk of infection include :  

• Certain types of cancer and cancer treatments
• Having a central line, tube, or drain
• Mouth or throat sores
• Being in the hospital for a very long time
• Having had a bone marrow or stem cell transplant
• Having had an organ transplant
• Not getting enough sleep
• Poor nutrition
• Other medicines that affect your immune system (such as steroids)
• Having other heath conditions such as diabetes, heart or lung problems, or autoimmune disorders

Talk to your cancer care team about what might put you at higher risk for infection.

What types of cancer increase a person’s infection risk?

Some types of cancer can increase the risk for infection:

• Cancers that grow in the bone marrow and crowd out normal blood cells (such as leukemias, lymphomas, and multiple myeloma)
• Tumors that damage or break through tissues inside the body and let in germs.  

Which cancer treatments increase infection risk?

Some cancer treatments cause immune system problems for a short time. Others can cause long-term immune problems.

The most common cancer treatments that can increase risk for infection include:

• Surgery
• Chemotherapy
• Radiation therapy
• Immunotherapy
• Targeted drug therapy
• Bone marrow or stem cell transplant

Nutrition and infection risks in people with cancer

All cells need nutrients to work. Nutrients can include calories, protein, carbohydrates, fats, vitamins, minerals, and fluids.

For many people with cancer it can be hard to get enough nutrients because:

• The cancer itself can make it hard to eat or digest food. This is common in people with cancers of the digestive system, mouth, or throat.
• Cancer treatments such as  radiation therapy and chemotherapy can cause nausea and a loss of appetite (this can lead to developing a condition called cancer-related anorexia).
• Cancer cells use up nutrients, leaving less for normal, healthy cells.

 Poor nutrition, also called malnutrition,  can weaken a person’s immune system and make it harder for them to fight an infection if they do get sick. Poor nutrition and infection are two of the most common side effects of cancer and cancer treatment.

Learn more about what to eat during cancer treatment in Nutrition for the Person with Cancer.