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Mouth Soreness and Pain
Mouth soreness can be caused by some cancer treatments that irritate the lining of your mouth and throat. This can cause little blisters, cuts, or sores in the mouth or throat called oral mucositis or stomatitis.
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What causes mouth sores?
Cancer treatments are the most common cause of mouth sores in people with cancer. Treatments can damage the healthy cells that line the mouth and throat. This can cause painful mouth sores, redness, and irritation. In some cases, the sores can go down into the throat and farther down into the digestive tract. They may also increase your risk of dehydration, infection, and weight loss.
Treatments most likely to cause mouth sores include:
- Certain kinds of chemotherapy, which is sometimes called chemo mouth
- Targeted drug therapy, and immunotherapy medicines
- Radiation treatments to the head and neck
- Stem cell or bone marrow transplant
Mouth sores can appear 1 to 2 weeks after treatment starts and may come and go during treatment. They may take 2 to 4 weeks to fully heal after treatment ends.
Problems that may cause or make mouth sores worse
- Infection
- Dehydration
- Poor mouth care
- Alcohol or tobacco use
- Not getting enough of certain vitamins or protein
Mouth sores can be very painful and lead to swallowing problems, loss of appetite, and weight loss. They can also be costly to treat if they cause serious problems.
Symptoms of mouth sores
Mouth sores may look like blisters, cracks, or sores. They may be red or have white patches, and they might cause the following symptoms:
- Redness, patches, and swelling of the mouth and tongue. This swelling may continue down the throat and into the digestive tract. Your mouth may feel tender or irritated, making it difficult to swallow.
- Pain that can be mild to severe. Pain in the mouth and throat can make it difficult to chew and swallow food or fluids.
- Bleeding or infections in the mouth
- Dryness in the mouth
Prevention and treatment of mouth sores
The best way to manage mouth sores is to prevent them or treat them early.
Dental checkup and cleaning
Many cancer care teams suggest that you see a dentist before you start treatment. This allows you to get your teeth checked and cleaned. Dental checkups can help prevent and minimize mouth sores. This is even more important if you are going to have radiation to your head or neck.
Dentists or dental hygienists can show you how to care for your mouth. They can also treat cavities or oral infections before cancer treatment starts. Let your cancer care team know if your dentist suggests procedures or treatments before you start your cancer treatment.
Good mouth care and mouth rinses
Keeping your mouth clean and moist can help prevent mouth sores and lower the risk of infection. Good mouth care can also help mouth sores heal, keep them from getting worse, and make your mouth feel better.
- Use a soft toothbrush or foam swab to clean your mouth. This can help protect your gums and the lining of your mouth from irritation.
- If you use dental floss, ask your cancer care team if it’s safe to continue or if they recommend another way to clean between your teeth
- Rinse your mouth regularly with a bland mouth rinse, such as baking soda, salt water, or saline solution. These rinses can help keep your mouth clean and soothe discomfort.
- Avoid using mouthwashes that have alcohol in them. These can irritate and dry out your mouth, making you more likely to get mouth sores and have discomfort.
Some mouth rinses and home remedies might be harmful or make mouth sores worse.
Talk to your cancer care team before using or making any rinses at home to be sure these products are safe for you.
Medicines and treatments to prevent or manage mouth sores
Medicines and treatments may be used to prevent mouth sores or manage pain from sores. These include:
- Pain medicines to make it more comfortable to care for your mouth, eat, and drink. Medicines may be used as a rinse or may be taken as pills or a patch.
- Dexamethasone (a steroid) mouth rinse for painful and severe mouth sores.
- Mouth rinses with antibiotic agents if your mouth sores are infected.
- Lidocaine liquid pain medicine to be used as a swish and spit, especially before meals.
- Gelclair, a gel that you swish around the mouth and then spit out. It coats and soothes the inside of the mouth, which can help with pain from mouth sores.
- Palifermin, a growth factor drug that helps stimulate oral tissue. It may be used in some people getting high doses of chemotherapy or total body radiation to prepare for a bone marrow or stem cell transplant.
- Photobiomodulation therapy (PBMT), which uses low levels of light to help reduce inflammation and pain.
Some cancer care teams suggest using a mouth rinse that is a mixture of different medicines to help manage symptoms. What’s in the mixture will depend on where you are getting treated.
You may see mouth sore treatments online or hear about them from other people. But these may not be approved for treating your mouth sores. For example, methylene blue is an FDA-approved medicine for a rare blood disorder. It is not approved by the FDA for treatment of mouth sores.
Oral cryotherapy
Oral cryotherapy is one way to help prevent mouth sores from chemotherapy. You hold something cold in your mouth. This could be ice chips, special devices that cool the mouth, or other cold items, such as ice cream. You do this before, during, and after certain chemo medicines, such as melphalan and 5-fluorouracil (5-FU). The cold narrows blood vessels in the mouth. This means less chemo reaches the lining of the mouth.
Cryotherapy does not work for oral mucositis that has already formed. Recent research findings show that cryotherapy can help lower the risk of pain and severe oral mucositis in some situations. The timing and length of treatment can vary, so follow the instructions from your cancer care team.
Low-level laser therapy (LLLT)
Low-level laser therapy, also called photobiomodulation (PBM), uses low levels of light to help prevent or reduce mouth sores caused by cancer treatment. LLLT may also help to decrease inflammation and pain.
LLLT is recommended for some adults who are receiving a stem cell transplant or radiation to the head and neck. LLLT is also being studied in children. More research is needed to determine the best treatment methods for children. Talk with your care team about options that may help prevent or reduce mouth sores in children.
Treatments being studied for people with head and neck cancer
People with head and neck cancer who are getting radiation therapy alone or with chemotherapy are more likely to get mouth sores. In addition to standard treatments, some supportive or integrative approaches might help. Talk to your cancer care team before trying any of these options.
- Benzydamine mouthwash is a liquid nonsteroidal anti-inflammatory rinse. It may prevent or reduce inflammation and prevent mouth sores.
- Glutamine may help prevent mouth sores and reduce pain in some people getting radiation and chemotherapy.
- Honey might help prevent mouth sores by reducing inflammation.
- Morphine rinses may help relieve pain from mouth sores in people getting radiation and chemotherapy.
These products are still being studied in people receiving treatment for head and neck cancer. Research is needed to find out which products and doses are safest and most effective for people with these cancers.
Tips to prevent and manage mouth sores and pain
There are many things you can do to prevent or manage mouth sores. These tips can also help prevent infection and make your mouth more comfortable.
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Use a small flashlight, mirror, and a tongue depressor with gauze wrapped around the tip. If you wear dentures, take them out before you check your mouth. Tell your healthcare team if your mouth looks or feels different or if you notice changes in how things taste.
Talk to your cancer care team about a mouth care plan that is right for you. Your cancer care team might recommend doing mouth care 30 minutes after eating and every 4 hours while you’re awake. Ask whether you should floss.
If you wear dentures, your cancer care team may suggest that you remove and clean them during your mouth care. It might also help to wear them less. Try taking them out at night and between meals. Ask if it’s okay to wear your dentures while waiting for the sores to heal.
- Keep your lips moisturized with a lip balm.
- Drink at least 2 to 3 quarts of fluids each day if your cancer care team approves.
- Ask about medicine that can be swished in your mouth 15 to 20 minutes before meals or dabbed on a painful sore.
- Eat chilled foods and fluids, such as popsicles, ice chips, frozen yogurt, sherbet, or ice cream.
- Eat soft foods that are not too dry and easy to swallow. You might mash or puree foods in a blender to make them easier to eat.
- Use a straw.
- Eat small, frequent meals of bland, non-spicy foods.
- Avoid raw vegetables and fruits, and other hard, dry, or crusty foods, such as chips or pretzels.
- Avoid alcohol and tobacco.
- Avoid acidic fruits and juices, such as tomato, orange, grapefruit, lime, or lemon.
When to contact your cancer care team
Contact your cancer care team if you:
- Have redness or shininess in your mouth that lasts for more than 48 hours (2 days)
- Have bleeding from your gums
- Notice any type of cuts or sores in your mouth
- Have white patches on your tongue or inside of your mouth
- Have not been able to to eat or drink much in the last 2 days because of mouth pain
- Can’t take medicines because of mouth sores
- Have a fever with a temperature of 100.5°F (38°C) or higher
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
American Society of Clinical Oncology. Mouth Sores or Mucositis. Accessed at cancer.net. Content is no longer available.
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Oncology Nursing Society. Symptom interventions: Mucositis. Accessed at https://www.ons.org/pep/mucositis on October 30, 2026.
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Last Revised: October 30, 2026
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