Has your oncology team mentioned that mouth sores might be a side effect of your treatment? If so, we’re here to help. This side effect can be painful and distressing, but there are ways to prevent and treat mouth sores to keep you as comfortable as possible, help you continue to eat and drink normally, and keep them from becoming infected or severe.  

What are mouth sores 

Cancer-related mouth sores appear on the inside lining of your mouth or throat. They often have a burn-like appearance and can range from a minor discomfort to a painful side effect that can make it challenging to eat and drink.  Signs of mouth sores include: 

• Redness or soreness anywhere in your mouth 

• Cracks, ulcers, blisters, white patches, or bleeding in your mouth 

• Dry mouth (lack of saliva) 

• Trouble chewing or swallowing 

• Pain in your teeth, gums, tongue, or jaw 

What causes mouth sores 

Cancer-related mouth sores are a common side effect of certain cancer treatments. Treatments that can sometimes result in mouth sores include chemotherapy, immunotherapy, and radiation to the head/neck. The reason mouth sores occur is because, like cancer cells, the cells that make up the tissue inside the mouth are ones that grow quickly. Some chemotherapy treatments target all quickly growing cells in the body including healthy ones which can lead to common side effects such as mouth sores. 

The timeframe you may experience mouth sores depends on which kind of treatment you are receiving: 

• Chemotherapy: Mouth sores caused by chemotherapy often form a few days after treatment. The length of time mouth sores last varies based on the type and dose of chemotherapy you are receiving..  

• Radiation:Mouth sores caused by radiation to the head and neck usually form sometime after the end of the second week of treatment, and can even start up to a week after treatment is complete. Mouth sores from radiation typically take 4-6 weeks to heal after treatment ends.  

• Immunotherapy: Mouth sores caused by immunotherapy drugs form within 1-2 weeks of starting treatment and clear up within 2-3 weeks after treatment ends. 

• Targeted treatments: Certain targeted therapies, including many oral treatments can cause mouth sores and mouth pain. Sometimes these sores can resemble canker sores. Some patients may have mouth pain with no visible sore.  These symptoms may resolve over time on the treatment, or with scheduled treatment breaks as prescribed. 

If your treatment involves a bone marrow transplant, mouth sores can also be a sign of graft-versus-host disease (GVHD), a common and treatable side effect. If you experience mouth sores after a bone marrow transplant, you should contact your doctor as soon as possible.  

Preventing & Treating Mouth Sores 

With appropriate prevention and management measures, mouth sores can be managed to keep you comfortable, help you to eat and drink normally, prevent infection, and keep your teeth and gums healthy. Here are our top tips to keep you feeling as well as possible during treatment: 

Get a dental checkup before starting treatment.

If possible, have a dental checkup before starting treatment. Dental procedures ARE NOT recommended after initiation of treatment. If you have already started treatment, consult your oncologist PRIOR to any dental appointments or procedures. It is also important to make sure your dentist is aware of your cancer diagnosis, treatment regimen, etc. If you have untreated tooth decay or cavities, that can increase your risk of infection and mouth sores once treatment begins.  

Practice good oral hygiene. 

• A daily routine of oral care can help reduce risk for infection.  

• Brush your teeth, gums, and tongue VERY gently three times daily using a very soft toothbrush moistened with warm water and a fluoride toothpaste. Be careful not to cause any additional trauma to gums with aggressive brushing.   

• Floss once per day, if you are able to do so without pain or bleeding. If you have areas of bleeding or sores, avoid those areas until they heal. You can also use a water flosser (e.g. WaterPik) on the weakest setting to help prevent extra irritation.   

• Use alcohol-free mouthwash and toothpaste. Alcohol can further dry out your mouth and cause irritation. 

• Consider asking your dentist or doctor for a prescription mouth rinse that’s free of harsh chemicals but still offers clinical-grade cleaning. 

Rinse often.

• Rinse and wipe your mouth after eating to remove small pieces of food.  

• Perform an oral baking soda rinse to help get rid of any small particles of dirt in your mouth. Data shows these rinses help keep your mouth extra clean and improve comfort.*

• Mix a solution of one teaspoon of baking soda in a quart of water. Rinse with the solution every 4 hours.  

Keep your mouth and lips moist.  

• Why: Dry mouth often accompanies mouth sores, so staying well hydrated may help prevent sores from becoming more irritated.   

• Drink lots of water — 2-3 liters a day if you don’t have fluid restrictions during treatment.  

• Sip bland fluids like water, milk and protein shakes throughout the day.   

• Frozen fluids, like Popsicles, ice chips, ice cream, frozen yogurt and sherbet also provide hydration and may be soothing. 

• Use an artificial saliva product (like Biotene) if you find that your mouth is dry most of the time. Artificial saliva products can lubricate your mouth to prevent irritation. 

• Apply lip moisturizer often (like chap stick).

Take special care of dentures and removable appliances. 

• Clean dentures and appliances properly every day with an antibacterial agent. 

• Avoid wearing dentures while you sleep. 

• If you notice your dentures fitting looser or tighter, ask your dentist to adjust them. (Weight gain or loss during treatment can cause dentures to lose their fit, which can in turn cause injury or irritation). 

Monitor your mouth closely.

• Keep a close eye on any sores or areas of discomfort so that you can let your team know if things are getting worse.  

• If you notice white patches in your mouth, contact your oncology team as soon as possible. This could be an early sign of a treatable infection. 

Communicate with your team.

• Why: Unfortunately, mouth sores are sometimes impossible to prevent. If you do experience mouth sores during treatment, it is important to let your team know, as they will want to provide support to make sure you stay comfortable and free from infections.  

• If you do experience new or worsening sores, your oncology team might prescribe medication.

Nutrition and mouth sores 

One of the biggest challenges with mouth sores is that it can make eating and drinking uncomfortable. It’s important to continue to keep your nutrition and hydration up — here are some tips you can try:  

• Avoid foods that might be irritating due to sharp edges, acidity or spiciness, like:  

  • Oranges, grapefruit, lemons, pineapple, and other citrus fruit or juice  

  • Tomato sauce and tomato juice 

  • Raw vegetables, granola, toast, crackers, and other rough, crunchy, or dry foods 

  • Spices, seasonings, and condiments such as pepper, chili powder, curry powder, salsa, pepper sauces, horseradish, ketchup and vinegar 

• Exchange those foods for diet soft, bland, and moist foods which are less likely to cause discomfort: 

  • Fish, moist-cooked chicken, ground meat or turkey  

  • Yogurt, cheese and eggs  

  • Mashed regular or sweet potatoes, pasta, hot cereals or moist cold cereals 

  • Beans 

  • Cooked vegetables 

  • Soft fresh or canned fruits 

•  Add oil, butter, gravies, sauces and avocado to foods to boost their moisture and calorie content 

• Eat foods cold or lukewarm if hot temperatures are irritating  

• How you consume food can also make a difference.  These are other helpful hints:  

  • Consider drinking your calories via high-calorie protein shake supplements (like Ensure) instead of food that you have to chew 

  • Eat small amounts of food more frequently over the course of the day 

  • Use a straw  

If you're experiencing mouth sores, the Iris Care Team can help. From additional tips to medication interventions, our Nursing team is here anytime, any day. Chat with a Nurse to get help with mouth sores or other side effects now.