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For Everyone Touched By Cancer

Everything You Need To Know About Radiotherapy And Chemo Mouth Sores

Written by Oluwatoyin Joy Oke on 
10th January, 2023
Updated: 29th January, 2024
Estimated Reading Time: 6 minutes

Are you undergoing cancer treatment, radiation therapy (to the mouth or neck) or chemo? Or are you preparing to start chemotherapy? Do you wonder why you have things like ulcers in your mouth? Do you know what they are? Over the years, many cancer patients using chemo drugs have experienced a condition known as mouth sores.

Chemotherapy treatment has many side effects; chemo mouth sore is one of them. This condition can make it very hard to eat and talk. You need not suffer from cancer sores during chemotherapy. Find out from this article what mouth sores are, how to stay more in control, and things to do to relieve your pain.

Mouth Sores or Mucositis

Mouth sores are the soreness of the mucous membranes in your mouth. Mouth sores are areas that look like small cuts, ulcers, and swelling in your mouth, and throat. They are also called mucositis if not properly treated.

Mucositis can prevent the production of little or no saliva, which helps to lubricate the mouth. It can make eating, talking, or even swallowing difficult for you.

Sore mouth or mucositis can prevent the continuation of your treatment if it becomes severe.

Your mouth and Cancer drugs

Sometimes chemotherapy or radiation therapy to the head and neck area can cause sore mouths. Some chemo also affects the mouth flavor making it hard to enjoy your meals. There are treatments for this and things that can help reduce your risk.

Please always notify your doctor if your jaw is swelling and your teeth are sore from cancer treatment. Doing this can help them provide palliative and supportive care for you.

What causes mouth sores?

Knowing the cancer treatment that will cause mouth sores will help your healthcare team manage it well.

Below are the leading causes of cancer-related mouth sores:

leading causes of cancer-related mouth sores

How long do mouth sores last?

Mouth sores usually appear a few days after starting treatment and disappear two to three weeks after the end of chemotherapy. And you can get rid of them within a week of treatment. Mouth sores after chemotherapy get worse around 1 – 2 days after treatment.

The healing time for your mouth sores if you had radiation therapy to your head and neck may take about 6-8 weeks. If your treatments involve a combination of chemo and radiation therapy it may take about 2 weeks to be free from mouth sores.

Mouth sores caused by cancer treatment often worsen about a week after chemotherapy. But everyone is different so the range may vary from person to person. After which, they improve a lot.

How can cancer treatment affect your mouth?

The different cancer treatments, sometimes harm the normal cells in your mouth in the process of killing the cancer cells. Some of these treatments can disturb the activities of the good bacteria in your mouth and expose you to different infections, which can cause mucositis or sore mouth.

This can lead to issues with your teeth, gums and even the gland in your mouth that produces saliva. The effects of cancer treatment or drugs depend on the individual and the amount used.  

You can’t predict what will happen but can prepare for whatever develops. You may experience dry mouth, bleeding gum, tooth pain, or taste changes. 

What do chemo sores look like?

A chemotherapy rash usually looks like small blisters with tiny pimples surrounded by pus. Those who develop such a rash will also experience pain.

What can I do to prevent mouth sores?

There is no right way to prevent mouth sores due to chemo, having a chat with your cancer healthcare team on your risk and things to do is a great way to start, but also try the following recommendations :

  • Talk to your doctor to recommend a dentist that cares for cancer patients. Visit this dentist before treatment starts. They will help to check the condition of your mouth. They can also help develop a good dental health plan and treat dental issues before treatments.
  • If you are doing dental work before your treatment, inform your dentist. Be sure to finish everything relating to your mouth at least a month before your cancer treatment for complete healing before chemo.
  • Tell your doctor if you experience previous mouth sores in your past treatment; they will help prevent it during treatment and help you feel better.
  • Stop smoking before starting your treatments if you smoke.
  • Develop a mouth care routine way before treatments
  • Develop the habit of regularly rinsing your mouth with this solution

This mixture includes: EITHER

  • 1 teaspoon of baking soda
  • 2 cups of water


  • 1 teaspoon of salt
  • 1 teaspoon of baking soda
  • 1 quart of water

Stir the solution very well, then gently swish it in your mouth before spitting it out.

How to care for your mouth during chemo treatment

Do the following during treatments:

  • Keep your mouth clean at all times: you can do this by gently and regularly brushing your teeth, gum, and tongue with a soft toothbrush after eating and before bed.
  • Pay attention to your month: inform your doctor immediately if you notice an ulcer, pain or sensitivity to cold or hot things.
  • Continue to use the above solution: use the salt and baking soda solution several times daily to keep your mouth moist. You may even ask your health care doctor to recommend a suitable mouthwash that is not alcohol based
  • Eat right: eat foods like fresh fruit and veggies; they can help prevent and fight infections during treatment. To reduce painful mouth sores, take more warm water and food. Avoid extremely cold foods and acidic foods. Consider eating room-temperature foods instead of hot food that can hurt your tender mouth during chemo.
  • Use ice chips or water: to reduce the pain from mouth sore due to chemo, always have ice chips or cold water in your mouth to stay hydrated
  • Floss gently: when you floss daily, it helps to reduce bacteria buildup in your mouth, increasing your risk of infection.
  • Avoid the use of dentures: if you wear dentures before treatment, reduce the number of times you wear them. Please don't wear it during meals and at night.
  • Rinse your mouth a few times daily: do not use mouthwash containing alcohol. Mix a small salty solution into your mouth, or rinse with cold water.
  • Protect your lips: consider using mild lip balm to keep your lips moist at all times.
  • Keep your mouth moist: this you can achieve if you drink plenty of water daily. Get yourself a fancy and handy water bottle to remind you to drink. You can even suck and chew on sugar-free candies and gums.

Do anti-inflammatories help with chemo mouth sores?

According to the American Cancer Society, the anti-inflammatory medication Benzydamine can be used to treat mouth soreness in people who did radiotherapy to the mouth and throat . Morphine rinses may also be used to ease mouth sores. Dexamethasone is used in mouthwashes for cleansing and irritation.

Treatment of mouth sores and pain

Dental check-ups before and during treatment, especially before head and neck radiation or chemotherapy will help stop and relieve sores.

Dentists can guide you on a good dental health plan and treat dental problems and cavities before cancer treatment. This can go a long way in helping you deal with mouth sores during treatment. Below are other things that can help:

Low-level laser therapy

Researchers show low lasers (LLLTs) help treat sore throats resulting from stem cell transplantation.


When cryotherapy is used, the patient sucks on ice chips before, during, and after short infusions of certain chemotherapy treatments. Some studies have shown this to help prevent mouth sores by decreasing tissue blood flow and limiting high chemical exposure from treatment.


Some vitamins can help with rashes or mouth sores, but you should consult with a medical professional before consuming any. Treatment options available to relieve mouth sores include the:

  • Painkillers, which may relieve discomfort and pain but do not help treat mouth ulcers.
  • Steroids or non-steroidal anti-inflammatory drugs can help with both healing and discomfort.
  • Palifermin helps oral tissue to grow fast, it has been used in some patients receiving radiation therapy to the head and neck, and in some receiving high-dose chemotherapy or stem cell transplants.

Final thoughts

Don't suffer from chemo-sore mouth on your own, talk to your Doctor, nurse or health care team who can help you deal well with mouth sores. Follow the tips in this article.

You can also share with us your experiences and other tips that can help with cancer mouth sores

Further reading

Chemo Hair Loss: Understanding and Coping with a Common Side Effect of Cancer Treatment

What Is Chemotherapy And Why Is It Given To People With Cancer?

Chemo Guides

Cooking For Chemotherapy

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