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Sore Mouth and Throat Due To Chemo : Causes, How Long Do These Sores Last, & Its Treatment

People who are undergoing cancer treatments may find themselves suffering from mouth, throat, and dental problems like sore mouth and throat. This is because radiation therapy, a common treatment for cancer, to the neck and head can cause harm to the salivary glands and tissues in the mouth. This makes it difficult to chew and swallow normally, as painful sores often develop in the mouth and throat. There are also certain types of immunotherapy and chemotherapy that cause harm to the cells in the mouth, throat, and lips. Furthermore, the drugs that are used to treat cancer and associated bone problems are also known to cause various oral problems. This is especially common if you have undergone a bone marrow (stem cell) transplant as part of your cancer treatment. Here’s everything you need to know about sore mouth and throat caused due to chemotherapy, their causes, and how to manage these side effects.

Sore Mouth and Throat Due To Chemo

Mouth and throat sores are common side effects of cancer treatment like chemotherapy. It is known as mucositis or stomatitis, meaning an inflammation of the tissues present inside your mouth. Due to chemotherapy, whitish ulcer-like sores develop on your cheeks, lips, tongue, gums, on the floor or roof of the mouth, and even the throat. And if you don’t get mouth ulcers, you may notice patches that feel swollen and painful in your mouth, as if your mouth has been burned.(12)

Cancer treatment can cause mouth and/or throat sores because the cells in the mucous membranes that line your mouth are rapidly growing cells, just like the cancer cells. Cancer treatments work by attempting to stop or slow down this rapid growth of the cancer cells, but since the cells in the mucous membranes of the mouth are also growing rapidly, the treatment tends to affect them as well. Furthermore, cancer treatments like chemotherapy can sometimes prevent these cells in the mouth from being able to repair themselves when they get damaged. This can also lead to sores.

Anyone receiving radiation therapy, chemotherapy, or a bone marrow transplant is more susceptible to developing mouth and throat sores as a side effect of these cancer treatments. Furthermore, if you already have existing conditions like dry mouth or gum disease, or if you do not have good oral hygiene, you are at a higher risk of developing mouth sores during your cancer treatment. People who smoke or drink alcohol regularly and women are at a greater risk of developing these sores.(3)

If you are undergoing chemotherapy, these sores can start forming anywhere between five days to two weeks after your first session. Depending on the exact cause, these sores can either disappear on their own in a few weeks’ time, or they could linger on for a longer time and need treatment to get resolved.(4)

It is necessary to find ways to manage the pain from these sores and to also keep an eye out for any signs of an infection. Cancer-related mouth sores can often lead to dehydration, weight loss, and many other serious complications if left untreated.

What Are The Different Mouth and Throat Problems That Can Develop From Chemotherapy?

For patients going through chemotherapy, mouth and throat problems may include:(5)

  • Mouth sores
  • Changes in smell or taste (known as dysgeusia)
  • Dry mouth (known as xerostomia)
  • Infections in the mouth or throat
  • Pain and swelling in the mouth
  • Sensitivity to cold or hot foods and drinks
  • Trouble swallowing (known as dysphagia)
  • Tooth decay in severe cases

You may begin to notice the symptoms within just a couple of days of having chemotherapy or even a few weeks after your cancer treatment. Here are some symptoms you may observe and feel as mucositis develops:

  • Open sores similar to ulcers or canker sores
  • Red or white patches in the mouth
  • Swelling
  • Pain
  • Bleeding
  • Sore throat
  • Difficulty swallowing, drinking, or eating
  • Necrosis or dead tissue

As the sores begin to heal, you may find that the sores start becoming slightly crusty. It is necessary to remain watchful of your symptoms to inform your oncologist if you see that the sores are not healing on their own. You should also contact a doctor at the earliest if you notice any of the following:

  • You develop a fever.
  • You start to lose weight due to being unable to eat or drink properly.
  • The sores become more painful, and the overall condition worsens.

Remember that if left untreated, mouth sores can lead to dehydration, malnutrition, and even life-threatening infections.

How Long Do These Sores Last?

The exact time period that your sores take to heal depends on the particular cancer treatment you are undergoing. For example, if you develop sores in the mouth and throat after chemotherapy, they should start healing within two to four weeks. However, this is so if there is no infection. If you have undergone radiation therapy, the sores may take a bit longer, usually around six to eight weeks. In chemoradiation accompanied by a stem cell transplant, the sores can heal within two weeks.(678)

Treatment of Mouth and Throat Sores Caused By Chemotherapy

There are numerous ways in which you can treat mouth and throat sores caused by chemotherapy, thus avoiding prolonged pain or an infection. These include:

  1. Practice Good Oral Hygiene

    It is very important to practice good oral hygiene. As the sores start to heal, you have to remember to clean the inside of your mouth correctly to prevent an infection. According to the recommendations of the National Cancer Institute, you should clean your teeth gently every four to five hours, especially before going to sleep at night. While brushing, there are some tips to keep in mind:(910)

    • Use a toothbrush that has very soft bristles for cleaning your teeth. You can further soften the bristles by running the toothbrush under hot water or keeping the toothbrush in a glass of hot water for a few hours.
    • Rinse your mouth with a mild mouthwash that does not contain alcohol. You can even rinse with plain water.
    • When, and if, the sores start becoming crusty, you can rinse your mouth with a homemade solution containing equal parts of saltwater or plain water with three percent hydrogen peroxide. However, restrict the use of this remedy to only twice a week, as it can possibly slow down the healing process of the sores.(1112)
    • Do not stop your daily flossing routine, but do it gently.
    • If you are in a lot of pain, you can use a little bit of topical oral pain medicine on the affected area. A good example is Orajel (benzocaine).(13)
  2. Consult a Dentist Before Starting Treatment

    It is recommended that before you begin your cancer treatment, you should visit your dentist once for a complete check-up and cleaning. Let your dentist know about your cancer treatment, and try to complete any dental work before you start your treatment.

  3. Rinse Your Mouth Regularly

    If you find that the pain from the sores is disrupting your ability to eat and drink, you should let your doctor know. In such cases, your doctor might treat the condition with an opioid mouthwash or a mouthwash containing lidocaine or doxepin.(1415)

    You can also try rinsing your mouth with mild saltwater or a solution of baking soda and plain water. Your doctor or your healthcare team may even recommend using a lubricating liquid known as artificial saliva to keep the insides of your mouth moist, as dry mouth is a common side effect of cancer treatment in some people. These are usually gel-like liquids, and you have to coat your mouth with a thin film to promote healing and ease the discomfort.

    Some more tips to help manage your mouth sores are:

    • Stop smoking or using any kind of tobacco-containing products.
    • Chew on ice chips to help numb any painful areas.
    • Restrict or avoid having salty, spicy, or acidic foods.
    • Use an over-the-counter oral pain medication to relieve the discomfort.
    • Opt for having soft food that does not need too much chewing.
    • Make sure to have your food at room temperature. It should not be too hot or too cold.
    • Keep rinsing your mouth throughout the day with cool water, salt water, baking soda solution, or a medicated rinse.
    • Eat fruits, vegetables, and plenty of good-quality proteins to maintain your overall health.
    • Take good care of your teeth and gums by following good oral hygiene.


Mouth and throat sores are one of the most commonly experienced side effects of cancer treatments like chemotherapy. You may notice that shortly after completing a round of chemotherapy, ulcer-like sores that are quite painful begin to develop on the inside of your mouth or throat. While these sores tend to heal on their own, if you find that they are interfering with your ability to eat and drink or they are worsening, you should visit your doctor that the earliest as they can cause some very serious complications if left untreated. This is why it is a good idea to schedule a visit with your dentist before starting cancer treatment so that your dental health is taken care of before you start chemotherapy.


  1. Anderson, P.M., Schroeder, G. and Skubitz, K.M., 1998. Oral glutamine reduces the duration and severity of stomatitis after cytotoxic cancer chemotherapy. Cancer: Interdisciplinary International Journal of the American Cancer Society, 83(7), pp.1433-1439.
  2. Aslam, M.S., Naveed, S., Ahmed, A., Abbas, Z., Gull, I. and Athar, M.A., 2014. Side effects of chemotherapy in cancer patients and evaluation of patients opinion about starvation based differential chemotherapy. Journal of Cancer Therapy, 2014.
  3. Mucositis (no date) Oral Cancer Foundation Information and Resources about Oral Head and Neck Cancer. Available at: https://oralcancerfoundation.org/complications/mucositis/ (Accessed: December 8, 2022).
  4. Beck, S., 1979. Impact of a systematic oral care protocol on stomatitis after chemotherapy. Cancer nursing, 2(3), pp.185-200.
  5. Bruya, M.A. and Madeira, N.P., 1975. Stomatitis after chemotherapy. The American Journal of Nursing, pp.1349-1352.
  6. Supportive, P.D.Q. and Board, P.C.E., 2021. Oral complications of chemotherapy and head/neck radiation (PDQ®). In PDQ Cancer Information Summaries [Internet]. National Cancer Institute (US).
  7. Specht, L., 2002. Oral complications in the head and neck radiation patient. Supportive care in cancer, 10(1), pp.36-39.
  8. Rose-Ped, A.M., Bellm, L.A., Epstein, J.B., Trotti, A., Gwede, C. and Fuchs, H.J., 2002. Complications of radiation therapy for head and neck cancers: the patient’s perspective. Cancer nursing, 25(6), pp.461-467.
  9. Epstein, J.B., Güneri, P. and Barasch, A., 2014. Appropriate and necessary oral care for people with cancer: guidance to obtain the right oral and dental care at the right time. Supportive Care in Cancer, 22(7), pp.1981-1988.
  10. McGuire, D.B., Fulton, J.S., Park, J., Brown, C.G., Correa, M.E.P., Eilers, J., Elad, S., Gibson, F., Oberle-Edwards, L.K., Bowen, J. and Lalla, R.V., 2013. Systematic review of basic oral care for the management of oral mucositis in cancer patients. Supportive Care in Cancer, 21(11), pp.3165-3177.
  11. O’Reilly, M., 2003. Oral care of the critically ill: a review of the literature and guidelines for practice. Australian Critical Care, 16(3), pp.101-110.
  12. Walsh, L.J., 2000. Safety issues relating to the use of hydrogen peroxide in dentistry. Australian dental journal, 45(4), pp.257-269.
  13. Khair-ul-Bariyah, S., Arshad, M., Ali, M., Din, M.I., Sharif, A. and Ahmed, E., 2020. Benzocaine: Review on a Drug with Unfold Potential. Mini Reviews in Medicinal Chemistry, 20(1), pp.3-11.
  14. Sarvizadeh, M., Hemati, S., Meidani, M., Ashouri, M., Roayaei, M. and Shahsanai, A., 2015. Morphine mouthwash for the management of oral mucositis in patients with head and neck cancer. Advanced biomedical research, 4.
  15. Shankar, A., Roy, S., Bhandari, M., Rath, G.K., Biswas, A.S., Kanodia, R., Adhikari, N. and Sachan, R., 2017. Current trends in management of oral mucositis in cancer treatment. Asian Pacific journal of cancer prevention: APJCP, 18(8), p.2019.
Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:December 14, 2022

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