This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on April 29, 2022.

Mucositis—a condition in which the mouth and digestive system lining become swollen and irritated—is a possible complication of cancer treatment.

Mucositis may be painful. It may also affect your eating habits. But it may be managed. If you develop mucositis as a side effect of treatment, ask your cancer care team how to manage any oral symptoms.

Causes and symptoms of mucositis

The cells found in the lining of the mouth are fast-growing. Chemotherapy and radiation therapy may inadvertently slow down or even stop these healthy, fast-growing cells from growing normally, thus stopping your mouth tissue from healing at its usual pace.

Both chemotherapy and radiation therapy may also interfere with the balance of healthy bacteria that are normally present in your mouth. In addition, radiation therapy may cause damage to tissue in the mouth and salivary glands, which produce saliva.

Mucositis manifests itself in a number of ways. Possible symptoms include:

  • Bleeding (this may happen with chemotherapy, but not with radiation)
  • Infection
  • Mouth sores
  • Oral pain and discomfort

Certain factors increase the risk of developing mucositis while you receive treatment for cancer, such as:

  • Receiving chemotherapy at high doses
  • Undergoing localized radiation at high doses in the head and neck areas, for the treatment of lymphoma and head and neck cancers

How to reduce your risk of mucositis

Be sure to include a dentist in your cancer care team, especially one who is experienced in treating oral complications caused by cancer treatments. Your dentist may perform a comprehensive examination of your oral health, especially before you start cancer treatment. Your dentist may assess you for:

  • Tooth decay
  • Gum disease
  • Ill-fitting dentures
  • Mouth infections or sores
  • Issues with jaw movement
  • Issues with your salivary glands

If you’re receiving certain kinds of treatments, such as chemotherapy, radiation therapy or stem cell transplant, at high doses, it’s important to form an oral care plan with your dentist in order to reduce the risk of oral complications like mucositis.

Furthermore, if you have head or neck cancer and you smoke, you’ll need to stop smoking in order to lower the risk of oral complications.

Managing and treating mucositis

Inform your cancer care team if you’re experiencing any of the symptoms of mucositis, because in addition to causing you pain, this side effect may impede your ability to speak, eat and drink if it becomes severe—possibly leading to malnourishment and dehydration. Your care team dietitian may be particularly helpful in offering evidence-based advice.

If you have mouth sores as a result of mucositis that make eating and drinking painful, some helpful strategies include:

  • Sticking to soft, easy-to-swallow foods, such as custards, milkshakes and scrambled eggs
  • Cutting your food into smaller pieces, and using a small spoon to take smaller bites of food
  • Making your food smooth with a food processor
  • Opting for cold or room-temperature foods, as hot foods may cause you pain
  • Drinking liquids out of a straw to help prevent beverages from making contact with parts of your mouth that hurt
  • Sucking on ice chips, which may numb your mouth and help alleviate pain
  • Avoiding spicy foods, citrus, ketchup and tomatoes, raw vegetables, salty foods, crunchy or sharp foods and alcohol
  • Asking your doctor about an oral glutamine dietary supplement, which may help reduce the severity of mucositis or prevent it altogether

If you develop a severe case of mucositis, your cancer care team may need to provide you with feeding tubes in order to make sure you stay nourished and hydrated.

Daily mouth care

It’s important to properly care for your mouth while you’re receiving treatment for cancer, because improper care may increase the bacteria in your mouth. Having too much bacteria in your mouth may lead to an oral infection, which may spread throughout your body.

When caring for your mouth, be sure to:

  • Brush your teeth and gums two to three times daily at intervals of two to three minutes each, using a soft-bristle toothbrush.
  • Use a fluoride-containing toothpaste.
  • Gently floss your teeth once daily.
  • Air-dry your toothbrush after each use.
  • If using toothpaste causes you pain, try brushing with a mixture containing 1 teaspoon of salt and 4 cups of water. For each brushing, use a clean cup to dip your toothbrush into a small amount of solution.