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Mouth soreness can be caused by little blisters, cuts, or ulcers. They can develop when there is irritation and swelling inside the mouth or throat (mucositis or stomatitis).
Cancer treatments are the most common cause of mouth sores in people with cancer. Cancer treatments can damage the cells that line the mouth and throat causing sores. Sometimes the sores go down into the throat and farther down into the digestive tract.
Some cancer treatments are more likely to cause mouth sores:
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.
Other problems that may cause or make mouth sores worse include:
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.
Mouth sores may look like blisters, cracks, or ulcers They may be red or have white patches and they might cause the following symptoms:
The best way to manage mouth sores is to prevent them or treat them early.
Many cancer care teams suggest that you see a dentist to get your teeth checked and cleaned before you start treatment. 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 and can treat cavities or oral infections before cancer treatment starts. Let your cancer care team know what your dentist suggests before starting treatment.
Keeping your mouth clean and hydrated can help prevent mouth sores and lower the risk of infection. It can also help mouth sores heal and keep them from getting worse. Good mouth care can also make your mouth feel better.
Because 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 it's right for you.
Medicines that may be used to prevent mouth sores or manage pain from them include:
Sucking on ice chips before, during, and after treatment is called cryotherapy. This only works for certain chemotherapies, melphalan (Alkeran) and 5-fluorouracil (5-FU), when they are given as short infusions. For these treatments, cryotherapy may help prevent mouth sores by narrowing blood vessels in the mouth and lowering exposure of the mouth lining to the chemotherapy.
Low-level laser therapy, also called photobiomodulation (PBM), might help prevent and speed healing of mouth sores in adults getting a stem cell transplant or radiation to the head and neck. LLLT appears to decrease inflammation and pain. Most studies have been done in adults, so it is not clear if LLLT is helpful in children as well.
People with head and neck cancer who are getting radiation alone or with chemotherapy are more likely to get mouth sores. Here are some treatments that might help them.
These treatments have not been studied in other types of cancer.
There are many things you can do to prevent or manage mouth sores. These steps will also help prevent infection and make your mouth more comfortable.
Check your mouth twice a day using 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 health care 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 if you should floss or not.
If you have 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.
Other tips include:
Get in touch with your cancer care team if you:
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.
American Society of Clinical Oncology. Mouth Sores or Mucositis. Accessed at cancer.net. Content is no longer available.
Elad S, Cheng KKF, Lalla RV et al. MASCC/ISOO clinical practice guidelines for the management of mucositis secondary to cancer therapy. Cancer. 2020;4423-4431.
Elad S, Yarom N, Zadik Y, Kuten-Shorrer M, Sonis ST. The broadening scope of oral mucositis and oral ulcerative mucosal toxicities of anticancer therapies. CA Cancer J Clin. 2022;72(1):57-77.
Franco R, Lupi E, Iacomino E, et al. Low-Level Laser Therapy for the Treatment of Oral Mucositis Induced by Hematopoietic Stem Cell Transplantation: A Systematic Review with Meta-Analysis. Medicina (Kaunas). 2023;59(8):1413. Published 2023 Aug 3.
Freedman K & Hole A. Gastrointestinal complications. In: Eggert JA, Byar KL & Parks LS, ed. Cancer Basics. Oncology Nursing Society; 2022: 313-331.
Oncology Nursing Society. Symptom interventions: Mucositis. Accessed at https://www.ons.org/pep/mucositis on February 26, 2024.
Last Revised: October 28, 2024
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
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