Mouth Sores

Updated 
August 31, 2015

Mouth sores, also called mucositisinfo-icon, are a side effectinfo-icon of some cancer medicines that cause the lining of your digestive system to become inflamed. Mouth sores often appear as ulcers on your lips or inside your mouth. Sometimes they can appear inside the esophagus, the tube that runs from your throat to your stomach. 

What Are the Symptoms of Mouth Sores?

Symptoms may include:

  • Red, shiny or swollen gums and mouth
  • Small sores on the soft tissues of your mouth or lips
  • A yellow or white film on your tongue or inside your mouth
  • Pain in your mouth or throat
  • Bleeding gums or mouth
  • White patches or increased mucus in your mouth
  • Pain, dryness or burning when you eat

Mouth sores can be uncomfortable and distressing. Pain from the sores can make it difficult to breathe, chew, swallow, talk, eat and drink. These issues can lead to poor eating, weight loss and dehydrationinfo-icon. If mouth sores become severe, they may become infected or bleed. Be sure to notify your doctor if you notice any symptoms of mouth sores.

What Causes Mouth Sores?

Mouth sores are caused by some chemotherapyinfo-icon and targeted therapyinfo-icon medicines used to treat breast cancer. They can also be caused by infectioninfo-icon, vitamin or proteininfo-icon deficiency, dehydrationinfo-icon, not keeping your mouth clean, alcohol or tobacco use and oxygen therapyinfo-icon.

Chemotherapy medicines that may cause mouth sores include:

If you get mouth sores during chemotherapy, they are likely to develop within your first 2 weeks of treatment. It usually takes 2 to 4 weeks for mouth sores to heal after treatment ends.

Targeted therapies that may cause mouth sores include:

Remember, not everyone who takes these medicines develops mouth sores. The symptoms and how severe mouth sores are can vary, too.

How Can I Reduce My Risk of Developing Mouth Sores?

Here are some ways you can try to prevent mouth sores:

  • Visit a dentist before you get treatment to make sure your teeth and gums are healthy
  • Practice good oralinfo-icon hygiene
    • Use a soft toothbrush to brush your teeth several times a day. Rinse your toothbrush in hot water and store it in a cool place
    • Floss every day
    • Avoid mouthwash with alcohol, as it can be drying. Instead, rinse your mouth with a homemade mix. Swish and spit before and after meals and before bed with either a half teaspoon of table salt or baking soda mixed in 8 ounces of water
  • Eat healthy, nutritious food including plenty of fruits and vegetables
  • Drink plenty of fluids. Try to drink 8-10 glasses of non-alcoholic, non-caffeinated beverages daily
  • Talk to your doctor if you have a history of mouth sores. Your doctor may be able to prescribe a medicineinfo-icon to prevent them during treatment
  • Stop smoking

Your doctor may also recommend medicines to improve the health of your mouth cells. Some women report success using cold therapyinfo-icon, such as swirling ice chips around in your mouth before treatment, to prevent mouth sores.

How Can I Manage Mouth Sores?

To treat mouth sores, you will want to try to prevent them from getting worse, lessen your risk for infectioninfo-icon and manage any pain until your mouth heals after you finish treatment. Your providers may suggest:

  • Applying medicineinfo-icon to the sores to manage pain and protect them
  • Avoiding foods that are acidic, alcoholic, salty or spicy, because they cause pain
  • Avoid smoking or tobacco products
  • Keeping your mouth clean and using oralinfo-icon rinses with salt or baking soda after every meal and before bedtime
  • Eating small mouthfuls of chilled, soft food
  • Using a straw to drink

If you have metastaticinfo-icon breast cancer, learn more about ongoing treatment and mouth sores.