Coping With Chemotherapy-Induced Mouth Sores

Mouth sores can be a nuisance during chemotherapy; not only due to the discomfort they cause but also from the limitations they can pose on eating and sometimes even talking. Symptoms can include redness, sometimes open sores, and burning in the mouth. Some foods, as well as smoking, can exacerbate the symptoms and increase the risk of developing an infection (such as thrush) in your mouth. Thankfully, an awareness of things that can either ease or worsen mouth sores can help make this common side effect much more tolerable for many people.

A man putting toothpaste on his toothbrush
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Inflammation of mucous membranes in the mouth sometimes referred to as stomatitis or mucositis often begins a few days after starting chemotherapy and can last for several weeks. Radiation therapy and surgery can cause inflammation in the mouth as well, and symptoms may be worse if you are receiving a combination of chemotherapy and radiation treatments for your cancer.

Symptoms and signs include a burning type of pain and redness involving the floor or roof of the mouth, cheeks, gums, tongue, and lips. White patches can appear which turn red after the tissue sloughs. Mouth pain can make eating difficult and may make talking and swallowing uncomfortable.


Understanding why mouth sores occur can sometimes make them just a bit more tolerable. Since chemotherapy attacks rapidly dividing cells (like cancer cells), it can also affect the rapidly dividing cells lining the mouth. Chemotherapy may also affect the production of saliva, and alter the normal bacteria present in the mouth, making infections more likely.

Chemotherapy Drugs Most Likely to Cause Mouth Sores

Most chemotherapy drugs can cause mouth sores and 20 percent to 80 percent experience this side effect, but it's more common with some drugs for lung cancer including:

  • Taxotere (docetaxel)
  • Adriamycin (doxorubicin)
  • VePesid (etoposide)
  • Taxol (paclitaxel)
  • Alimta (pemetrexed)

These medications are used often, particularly with breast cancer chemotherapy, and therefore mouth sores are very common among people being treated for cancer.

Almost everyone who receives radiation to the head and/or neck region will experience mouth sores as well.


Good oral care is the first step in coping with, and decreasing the discomfort from mouths sores. It is a good idea to see a dentist familiar with the dental effects of chemotherapy before beginning treatment to make sure your teeth and gums are as healthy as possible. Ask your dentist about alternative toothbrushes if you should develop soreness.

Oral care

Good oral care is essential not only to manage mouth sores but as part of caring for yourself with cancer. We are learning that gum disease is linked with inflammation, and inflammation has been associated with an increased risk of developing cancer. It's thought that inflammation may also play a role in the progression of cancer or recurrence.

  • Brush regularly, preferably after every meal. Gum disease can worsen symptoms.
  • If brushing is uncomfortable, options include using an extra soft toothbrush or a foam swab. Rinsing your toothbrush under hot water prior to brushing to soften the bristles may help. It may be best to avoid electric toothbrushes.
  • Keep your mouth moist throughout the day.
  • Using lip balm may ease discomfort, but choose a gentle product without chemical irritants.
  • Avoid mouthwashes, especially those containing alcohol. Instead, you might try a cup of warm water mixed with 1 tsp of baking soda.
  • If you wear dentures, try to remove them more frequently.

Your Environment

The air you breathe and the company you keep can affect how your mouth sores feel.

  • Don’t smoke
  • Some people are uncomfortable dining out in public due to dietary limitations with mouth sores. Invite friends over, and make suggestions on what they can bring. The distraction of friends and family might help when eating is painful.

Foods to Eat and Avoid

Taking some time to think about what you can and cannot eat will pay off in big dividends. It's much easier to limit problem foods before they cause problems than to cope with a sore mouth as a reminder.

  • Eat a good diet with a variety of foods. Some vitamin deficiencies can make symptoms worse, and a good diet may help your body fight off infections.
  • Avoid foods that are spicy, salty, or foods with citrus acid and tomato juice. Pineapple and strawberries are often tolerated better than other fruits, and grape or apple juice may cause less discomfort than citrus and tomato juices.
  • Limit your intake of alcohol
  • Avoid foods with extreme temperatures
  • Drink plenty of water
  • Avoid foods that are sharp, such as crackers, toast, and dry cereal
  • Try adding moist foods over dry foods, such as using gravy and sauces
  • Good food choices can include mashed potatoes, cooked cereals, applesauce, cottage cheese, pudding, yogurt, smoothies (without citrus), soups, Jello, baby food, or food pureed in the blender
  • Drinking liquids through a straw is sometimes very helpful in keeping the fluids away from tender mouth sores


Most of the time mouth sores can be managed by diet and good oral hygiene until they resolve on their own. Some oncologists may recommend artificial saliva, or topical agents to treat pain. In severe cases, cryotherapy or laser therapy has been used at a few cancer centers, and new medications designed to promote regrowth of tissues in the mouth are being tested in clinical trials.


Mouth sores can be an uncomfortable side effect of chemotherapy, but sometimes they can lead to more serious problems as well. Infections can develop (bacterial, fungal, or viral) especially if your white blood cell count is lowered from chemotherapy (chemotherapy-induced neutropenia). Bleeding may occur, especially if your platelet count is low (chemotherapy-induced thrombocytopenia). Pain can become quite severe for some people, requiring stronger pain management. Malnutrition and dehydration may occur if the pain and sores are interfering with your ability to take in adequate nutrition or fluids.

Considering the different side effects of chemotherapy, mouth sores may seem low on the list as far as seriousness, but that's simply not true. Mouth sores can lead to weight loss, and weight loss in people with cancer can be very serious. In fact, cancer cachexia, a syndrome which includes weight loss among other symptoms, is considered to be the direct cause of death for 20 percent of people with cancer. Don't hesitate to call your healthcare provider if you are suffering from this common complication.

When to Call Your Healthcare Provider

Make sure to let your oncologist know of any symptoms you are having during your chemotherapy treatment, including mouth sores. Some reasons to alert your healthcare team between appointments include:

  • Mouth sores that interfere with your ability to eat or drink
  • Significant weight loss or signs of dehydration
  • A white coating on your tongue, increasing redness, or bleeding that may be a sign of an infection
  • A fever. Ask your oncologist what temperature he or she feels is a concern and should prompt you to call

A Word From Verywell

Mouth sores can sometimes lead to complications in weight loss. But the primary reason to care for your mouth with mouth sores is to make sure your quality of life is as good as possible during your cancer treatment. With treatments available that can now limit the impact of nausea and vomiting as well as low white blood cell counts, many people are living active lives throughout chemotherapy. Make sure to speak up and talk to your healthcare provider if your mouth sores are compromising your ability to live your best life while in treatment.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Idayu Mat Nawi R, Lei Chui P, Wan Ishak WZ, Hsien Chan CM. Oral Cryotherapy: Prevention of Oral Mucositis and Pain Among Patients With Colorectal Cancer Undergoing Chemotherapy. Clin J Oncol Nurs. 2018;22(5):555-560. doi:10.1188/18.CJON.555-560.

  3. Lalla RV, Bowen J, Barasch A, et al. MASCC/ISOO clinical practice guidelines for the management of mucositis secondary to cancer therapy. Cancer. 2014;120(10):1453-61. doi:10.1002/cncr.28592

  4. Porporato PE. Understanding cachexia as a cancer metabolism syndrome. Oncogenesis. 2016;5:e200. doi:10.1038/oncsis.2016.3

Additional Reading

By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."