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Cancer Treatment and Your Mouth

Chemotherapy and radiotherapy to the head and neck often cause mouth problems. Here is what can happen, why a dental check before treatment matters, how to care for your mouth, and when to call your team urgently.

Updated September 2026·By the OHA editorial team·7 min read·How we write
Key takeaways
  • Chemotherapy and radiotherapy to the head and neck commonly cause a sore mouth, ulcers, a dry mouth, infections such as thrush, and changes in taste.
  • See a dentist before treatment starts if you can, so problem teeth are dealt with first.
  • Gentle, regular mouth care with a soft toothbrush helps. Tell your team early about any problems: they can prescribe mouthwashes, painkillers and other treatments.
  • Radiotherapy to the head and neck can leave a long-term dry mouth and a higher risk of tooth decay. Some bone-protecting medicines carry a rare risk of jaw problems.
  • A high temperature during chemotherapy can be a sign of a serious infection. Call your treatment team's advice line straight away.

The US National Institute of Dental and Craniofacial Research (NIDCR) says most people treated for cancer develop problems in the mouth, which can make it hard to eat, talk and swallow. Your cancer team's advice always comes first.

Why does cancer treatment affect the mouth?

Chemotherapy and radiotherapy kill fast-growing cells, including healthy cells lining the mouth (NIDCR). The US National Cancer Institute (NCI) adds that chemotherapy can lower the number of white blood cells (the cells that fight infection), and that radiotherapy can directly damage the tissues, salivary glands (the glands that make saliva) and bone. Cancer Council Australia says most changes gradually improve after treatment.

What mouth problems can happen?

A sore mouth and ulcers (mucositis)

Oral mucositis is inflammation of the lining of the mouth. The NHS describes a mouth that feels as if burned by very hot food, with ulcers, bad breath and discomfort when eating, drinking or talking. It says symptoms usually begin around a week after starting chemotherapy, or about 2 weeks after starting radiotherapy. The NCI says mucositis from chemotherapy usually heals by itself in 2 to 4 weeks if there is no infection, while mucositis from radiotherapy usually lasts 6 to 8 weeks. See also mouth ulcers.

Dry mouth

The NCI says saliva usually starts to decrease within a week of starting radiotherapy to the head or neck and may partly recover in the first year, but usually not completely if the salivary glands were in the treated area. The salivary glands usually return to normal after chemotherapy. See dry mouth.

Infections

Thrush, a fungal infection that causes white patches, is common. Cancer Research UK says infection is more serious during cancer treatment and needs treating quickly, so tell your doctor or nurse if you notice white patches in your mouth or on your tongue. See oral thrush.

Tooth decay and taste changes

NIDCR says radiotherapy to the head and neck can cause severe tooth decay, because without enough saliva decay and infections can develop. Food may taste metallic, bitter or salty, or everything may taste the same (Cancer Research UK). The NCI says taste returns to normal a few months after treatment for most people having chemotherapy, but for many people who have had radiotherapy the change is permanent.

Jaw stiffness and jawbone problems

Radiotherapy or surgery to the head and neck can make the jaw muscles stiff, called trismus (Cancer Research UK). For people having head and neck radiotherapy, NIDCR suggests opening and closing the mouth as far as you can without pain, 20 times, three times a day.

The NCI says radiotherapy can destroy tiny blood vessels in the jawbone, which can kill bone tissue and lead to fractures or infection. Cancer Research UK calls this osteoradionecrosis.

Some bone-protecting medicines, bisphosphonates and denosumab, can occasionally cause osteonecrosis of the jaw (death of bone tissue in the jaw). Cancer Research UK describes it as rare, with the risk highest for people having monthly treatment for cancer that has spread to the bones. Symptoms include pain, swelling or gum infections, bone showing in the mouth, loose teeth, gums that heal poorly after dental work, and numbness or heaviness in the jaw. It says to tell both your cancer doctor and your dentist straight away if you notice any of these.

Why see a dentist before treatment?

The NCI says treating decay, broken teeth, loose fillings and gum disease before treatment may mean fewer or milder complications. Cancer Council Australia says dental work may not be recommended during treatment because of a higher risk of bleeding or infection.

The sources suggest different timings:

  • NIDCR (US): about 1 month before treatment, and give your dentist your cancer doctor's contact details so they can talk to each other.
  • NCI (US): at least a month before, which usually allows time for the mouth to heal if dental work is needed.
  • Cancer Research UK: before radiotherapy to the mouth, usually at least 2 weeks before treatment begins. The dentist may remove unhealthy teeth first.

Cancer Research UK says fluoride treatment may help protect your teeth during radiotherapy, and advises a dental check before starting bisphosphonates or denosumab. The NCI and Cancer Council Australia advise stopping smoking. See smoking, vaping and oral health.

How should you look after your mouth during treatment?

Follow the routine your team gives you. General advice from the NHS, Cancer Research UK and the NCI includes:

  1. Brush gently with a soft toothbrush, at least twice a day (NHS) or after each meal as well (Cancer Research UK).
  2. Use a mild fluoride toothpaste. The NCI says flavouring, especially mint, may irritate a sore mouth.
  3. Rinse often with warm water, salt water (half a teaspoon of salt in a glass of warm water) or a mild alcohol-free mouthwash. The NHS says not to use alcohol-based mouthwashes.
  4. Keep your mouth moist: sip water, suck ice, chew sugar-free gum and use lip balm. Your team can prescribe saliva substitutes (NHS).
  5. Choose soft, moist foods, and avoid hot, spicy, salty, acidic or hard foods, alcohol and smoking (NHS, Cancer Research UK).
  6. Dentures: the NHS suggests leaving them out while your mouth is sore, kept clean and moist, but Cancer Research UK cautions against leaving them out for long periods, as your gums can change shape.

Flossing: the sources differ. The NHS says to floss once a day if you can, and the NCI says most people can floss safely while blood counts are low. Cancer Research UK says your doctor may advise against it if your platelet count (the cells that help blood clot) is low, because it can make your gums bleed, and Cancer Council Australia says to check with your dentist. Ask your team.

Cancer Research UK says it is much better to take painkillers and be able to eat and drink than to go without them.

After treatment

After radiotherapy to your mouth, Cancer Research UK says to have dental check-ups more often and always tell your dentist before any dental work, because your mouth will not heal as quickly and the dentist may need to talk to your radiotherapy doctor. If you take bisphosphonates or denosumab, it says to avoid invasive dental treatment such as extractions and implants (fillings and routine cleaning are fine), and not to stop the medicine without talking to your cancer specialist.

Tell your team or dentist
  • Your mouth or gums are very sore, or pain makes it hard to eat, drink or sleep (Cancer Research UK, NCI).
  • You have white patches, new sores or a very dry mouth.
  • You have jaw pain, swelling, numbness, loose teeth, bone showing in your mouth, or gums not healing after dental work.
Get help urgently
  • A temperature during chemotherapy can signal a serious infection (neutropenic sepsis). Cancer Research UK says to call your 24-hour advice line straight away if your temperature is 37.5°C or above, or below 36°C, or you have other signs of infection, including a sore mouth or a throbbing, painful tooth. Cancer Council Australia says to seek immediate medical attention for a fever of 38°C or higher, and the NCI says to call your doctor or nurse at 38°C (100.5°F) or higher. The NHS says to call your care team now if you have a high temperature, or NHS 111 if you are not sure how to contact them. The thresholds differ, so if in doubt, call.
  • Cancer Research UK says to call 999 or go to A&E (or your local emergency number) immediately if you have slurred speech or confusion, extreme shivering or muscle pain, have passed no urine in a day, are severely breathless, feel like you are going to die, or your skin is mottled or discoloured.
  • If your mouth is so sore that you cannot swallow, eat or drink, tell your team straight away (Cancer Research UK, NCI).

Frequently asked questions

Can I have dental treatment during cancer treatment?

Talk to your cancer team first. Cancer Council Australia says it may not be recommended, because of a higher risk of bleeding or infection.

Does Medicare in the US pay for dental care linked to cancer treatment?

Sometimes. Medicare says it may cover a procedure such as an extraction to treat a mouth infection before chemotherapy, and treatment for complications during head and neck cancer treatment, although it does not cover most routine dental care. See dental costs and help.

Where can I get support?

In the UK, Cancer Research UK's nurses are on freephone 0808 800 4040, 9am to 5pm, Monday to Friday. In Australia, Cancer Council is on 13 11 20.

Sources

  1. Cancer treatments and oral health, NIH National Institute of Dental and Craniofacial Research, accessed September 2026
  2. Mouth and throat problems: cancer treatment side effects, National Cancer Institute, accessed September 2026
  3. Oral complications of cancer therapies (PDQ), patient version, National Cancer Institute, accessed September 2026
  4. Mucositis, NHS, accessed September 2026
  5. Chemotherapy, NHS, accessed September 2026
  6. Side effects of radiotherapy, NHS, accessed September 2026
  7. Mouth problems and treatments, Cancer Research UK, accessed September 2026
  8. Mouth care, Cancer Research UK, accessed September 2026
  9. Head and neck radiotherapy side effects, Cancer Research UK, accessed September 2026
  10. Jaw problems (osteonecrosis) and cancer treatment, Cancer Research UK, accessed September 2026
  11. Sepsis, infection, and cancer, Cancer Research UK, accessed September 2026
  12. Mouth health, Cancer Council Australia, accessed September 2026
  13. What is neutropenia?, Cancer Council Australia, accessed September 2026
  14. Dental services, Medicare.gov (US Centers for Medicare and Medicaid Services), accessed September 2026

This article is general information about oral health. It is not a diagnosis or a substitute for advice from a dentist or doctor who knows your situation. If you have pain, swelling, bleeding that does not settle, or a problem that is getting worse, see a dental professional. In an emergency, contact your local emergency service.

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