Approved by the Cancer.Net Editorial Board, 08/2018

An infection occurs when the body's immune system does not quickly destroy harmful substances. Both cancer and its treatment weaken the immune system. This means that people with cancer are more likely to develop infections.

About the immune system

The immune system fights bacteria, viruses, and fungi that try to invade the body. The immune system includes these body parts:

  • The skin

  • The spleen

  • Lymph nodes

  • Bone marrow, which is the spongy, fatty tissue found inside larger bones

  • White blood cells called leukocytes and neutrophils, which help fight infections and destroy harmful substances

A low level of white blood cells is called leukopenia. This condition increases the risk of developing dangerous infections. Neutropenia is a type of leukopenia. It means a low level of neutrophils. Neutrophils are the most common type of white bloods cells.

Signs and symptoms of an infection

Infections may start almost anywhere. Common places where infections can start include:

  • The mouth

  • The skin

  • The lungs

  • The urinary tract

  • The rectum

  • The genitals

Signs of infection include:

  • A fever, which is a temperature of 100.5°F (38°C) or higher

  • Chills or sweating

  • Sore throat, sores in the mouth, or a toothache

  • Abdominal pain

  • Pain near the anus

  • Pain or burning when urinating or frequent urination

  • Diarrhea or sores around the anus

  • A cough or shortness of breath

  • Redness, swelling, or pain, particularly around a cut, wound, or catheter placement

  • Unusual vaginal discharge or itching

Infections are treatable. But they can be serious and potentially life-threatening. Managing symptoms and side effects is an important part of cancer care. This approach is called palliative care or supportive care. Talk with your health care team if you experience signs of an infection or changes in symptoms that you experience.

Risk factors for developing an infection

The following factors can affect white blood cells and weaken the immune system:

  • Lack of sleep, stress, poor nutrition, and other side effects

  • Chemotherapy

  • Radiation therapy given to large areas of the body or to the pelvis, legs, chest, or abdomen

  • Cancers that affect the bone marrow directly, such as leukemia and lymphoma

  • Cancers that spread to the bone

  • Other conditions that increase the risk of infection, such as diabetes, kidney disease, high blood pressure, congestive heart failure, an autoimmune disease, liver disease, chronic bronchitis, or emphysema

  • Medications for other conditions that weaken your immune system

Treating infections

Neutropenia, chemotherapy, or radiation therapy may place you at a higher risk of infection. In that case, you may receive preventive antibiotics or antifungal medications. This means the anti-infection medication is given before an infection starts.

In other cases, you may receive medication after developing an infection. If you develop neutropenia with a fever, you may need to stay in the hospital until the infection is gone.

If you have a high risk of developing neutropenia with a fever, your doctor may prescribe medications called white blood cell growth factors. These drugs help the body make more white blood cells. This reduces the risk of an infection. Learn more about ASCO’s recommendations for white blood cell growth factors.

Tips for preventing infections

There are steps you can take to help prevent infections:

  • Get plenty of rest.

  • Eat a well-balanced diet.

  • Avoid contact with people who are sick.

  • Do not share food, cups, utensils, toothbrushes, or makeup.

  • Wash your hands thoroughly and frequently, or use antibacterial hand sanitizers. This is important especially after using the bathroom and before eating.

  • Shower or bathe daily.

  • Apply lotion to prevent dry and cracked skin.

  • Be careful using sharp objects, such as scissors or knives. To avoid cuts, consider using an electric shaver and a blunt nail file instead of nail clippers.

  • Do not eat raw foods, including meats, shellfish, and eggs. And wash raw fruits and vegetables. Learn more about food safety.

  • Do not change cat litter or handle animal waste.

  • Use gloves during gardening and housework, especially while cleaning.

  • Clean your teeth and gums with a soft toothbrush. Use a mouthwash to prevent infections if your doctor or dentist recommends it. Learn more about dental health during cancer treatment.

Related Resources

When to Call the Doctor During Cancer Treatment

Side Effects of Chemotherapy

Side Effects of Radiation Therapy

More Information

National Cancer Institute: Infection and Neutropenia during Cancer Treatment

Centers for Disease Control and Prevention: Preventing Infections in Cancer Patients