Chemotherapy (chemo) can damage the cells lining the mouth, throat, and gastrointestinal tract. This damage is called mucositis. Mucositis affects the mouth as painful mouth sores, called stomatitis. This chemo side effect is common with certain chemo medications and can be very painful.


Symptoms typically start around 7 to 10 days after the start of chemo. Mouth sores, also called ulcerations, may feel hot and look red. Your tongue may swell and look as if it has a coating on it. Talk to your doctor and care team if you think you have mouth sores.

Treating mouth sores is important because pain from mouth sores may make it difficult to eat, talk, or swallow. In addition, open sores in the lining of the mouth may allow bacterial, fungal, or viral organisms to enter the body and cause infection


Certain factors are known to increase the chances of getting mouth sores:

  • Poor oral health prior to and during treatment
  • Having other diseases in addition to cancer

What You Can Do

  • Do not use mouthwashes with alcohol. Rinse out your mouth several times a day with a cup of warm water mixed with 1/4 teaspoon baking soda and 1/8 teaspoon salt. Then rinse your mouth out with plain water.
  • Brush your teeth, tongue, and gums gently with an extra-soft toothbrush after every meal and at bedtime.
  • Sucking on ice chips before and during your chemo treatment may prevent mouth sores in some patients getting certain types of chemo. This technique is called cryotherapy.
  • There are special mouthwashes that may be available by prescription only. Ask your doctor if a prescription rinse would help treat your mouth sores.

Ask your doctor about the risks and benefits of these and other treatments for mouth sores.

Ask Your Doctor:

  • What can I do if I develop mouth sores?
  • Are they serious?
  • How can I prevent mouth sores?
  • Are there foods I should avoid?
  • Are there foods or drinks that can help?
  • Should I try a medicated mouthwash?

 Print this worksheet 
 and bring it to your next doctor's visit.

A Closer Look: Christine*
Christine is 39 years old. She is being treated for stage III breast cancer requiring neoadjuvant chemotherapy.
She has a dental exam and cleaning.
Christine's doctor advises her to use antibacterial toothpaste and to rinse with saltwater prior to chemo treatments.

*This is a fictional case study based on chemo patient experiences. Your experience is unique. Your doctor and care team will create a plan that will best treat your type of cancer and manage your chemo side effects.

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