Sore mouth (oral mucositis)

Sore mouth (oral mucositis) is a side effect of some treatments for lymphoma. This page gives general suggestions to help you manage the symptoms of oral mucositis.

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What is oral mucositis?




What is oral mucositis?

Oral mucositis affects the mucous membrane, which is the soft tissue that lines the inside of your mouth. It happens when the membrane becomes inflamed (swollen, red and painful) and causes symptoms such as:

  • pain when you swallow
  • mouth ulcers (sores)
  • dry, sore mouth and lips.

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What causes oral mucositis?

Having a sore mouth is a common side effect of treatment for lymphoma. As well as destroying lymphoma cells, chemotherapy and radiotherapy also damage the healthy cells in the mucous membrane. Some targeted therapies also cause sore mouth, although it is unclear how they do so.

With chemotherapy, sore mouth generally happens around 7 to 10 days after you start treatment. For most people, it clears up between day 14 and 21 of treatment.

Having chemotherapy-related oral mucositis once increases your risk of developing it again after your next treatment with chemotherapy or during your next cycle of chemotherapy.

Radiotherapy to the head and neck, particularly at high doses, can cause a sore mouth. It typically happens between 12 and 15 days after you begin treatment. The risk of sore mouth increases if you have both radiotherapy and chemotherapy.

A sore mouth can also happen after a stem cell transplant. This can be caused by both the high-dose chemotherapy and immunosuppressive drugs given as part of the transplant. Oral mucositis often happens around a week after you begin treatment.

A sore mouth usually gets better once you finish your treatment for lymphoma and your blood counts return to the levels they were at before you had treatment. Usually, this is about 2 to 3 weeks after chemotherapy, and 6 to 8 weeks after radiotherapy.

For some people, sore mouth lasts longer. This can happen if you have a low neutrophil count (neutropenia) that continues for a while.

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Self-management for oral mucositis

There are some simple steps you can take to help improve symptoms of oral mucositis. We give some general suggestions below but speak to your medical team for advice on how best to manage your specific symptoms. 

Diet, nutrition and lifestyle

It’s important to get a balanced and nutritious diet. However, a sore mouth can make eating difficult or painful. You might find it easier to eat soft foods, such as mashed potato, scrambled eggs or soup. Hot food can irritate your mouth so try eating your meals warm or cool. It’s also advisable to avoid spicy and citrus foods, alcohol and tobacco, all of which can cause irritation.

If you are losing weight, or you do not think that you are getting enough nutrients, ask your GP or nurse for advice.

Oral hygiene

If you have a sore mouth, it is important to keep your mouth clean in order to prevent infection:

  • Visit your dentist before you start treatment for lymphoma – you may not be able to have any dental work done during or soon after treatment because of increased risk of infection.
  • Rinse your mouth with water or a mouthwash after eating. Avoid mouthwashes that contain alcohol as these can cause further irritation. You could try a mouth rinse made using a pint of cooled boiled water mixed with a teaspoon of salt. If your mouth is painful, your medical team might prescribe a specific mouthwash, for example, one containing anaesthetic.
  • Clean your teeth twice a day using a soft-bristled brush. You could try using children’s toothpaste, which is milder than standard toothpaste.

Flossing can damage an already sensitive mucous membrane, which can let harmful bacteria into the bloodstream. If you regularly floss, do it gently if you continue to do it during your lymphoma treatment. If you do not floss regularly already, it is not recommended that you begin while you are having treatment.

Dry mouth

A dry mouth is very common when your mouth is sore. There are simple things you can try to help moisten your mouth.

  • Sip fluids throughout the day. If you find drinking painful, you could try using a straw to reduce discomfort. Keep straws clean – this minimises the amount of bacteria on them, which could easily get into your mouth. It is also more difficult to determine the heat of a drink through a straw, so take care not to scald your mouth. 
  • Eat moist foods (such as mousses, jellies and fruit).
  • Chew gum or suck a boiled sweet to trigger saliva production.
  • Ask your medical team about artificial saliva treatments.
  • Use a moisturiser or balm to protect your lips from dryness.

Pain relief

Pain is often one of the most distressing symptoms of a sore mouth. To help relieve pain, try sucking an ice lolly or an ice cube. 

Your medical team may also prescribe medications, such as:

  • topical medicines (which you apply to the inside of your mouth) to form a protective coating over the mucous membrane
  • analgesics (pain relief medications), such as benzydamine, codeine or opioids.

If you wear dentures, you may find it more comfortable to leave them out while you have oral mucositis. Keep dentures clean and moist even when you are not wearing them.

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Treatment for oral mucositis

Your medical team might prescribe medication to help prevent or treat oral mucositis. This is particularly likely if you have low neutrophils (neutropenia), a common side effect of chemotherapy. Neutropenia weakens your immune system and increases your likelihood of getting a harmful infection. 

Some drugs, for example the chemotherapy drug methotrexate, carry a high risk of causing oral mucositis. To lower this, your medical team might give you folinic acid, either as an injection or via drip (infusion) after your treatment.


If you develop an infection, you may need treatment with antibiotics. Antibiotics are given to prevent sepsis, which can be life-threatening.

Infection can be especially serious if your immune system is weakened (immunosuppression). You are immunosuppressed if you:

Seek medical advice straightaway if you have any signs of infection.

Cryotherapy (ice therapy)

Cryotherapy uses ice to cool your mouth. It is used with some types of chemotherapy to help prevent oral mucositis.

If cryotherapy is suitable with your chemotherapy drugs, you may be given ice, ice-cold water or an ice lolly around 5 minutes before you have chemotherapy. The cold temperature narrows the blood vessels in your mouth. This stops so much blood (containing the chemotherapy drugs) from reaching your mouth and causing oral mucositis.


Palifermin is a type of growth factor that boosts the growth of new cells in the mucous membrane. It can help treat the symptoms of sore mouth and prevent you from getting new mouth ulcers.

Palifermin is sometimes used if you have high-dose chemotherapy and radiotherapy before stem cell rescue treatment (as part of an autologous stem cell transplant). It is given by injection for a few days before you begin treatment.

Low-level laser therapy (LLLT)

Low-level laser therapy (LLLT) uses low energy beams of light. The beams are directed by a small probe at the mucous membrane of your mouth. This can help to:

  • reduce the severity of oral mucositis
  • speed up the healing of wounds such as mouth ulcers
  • bring down inflammation
  • lower pain.

LLLT is sometimes used with radiotherapy and chemotherapy. However, it needs specialist equipment and is only available in some specialist cancer centres. Your medical team can advise on whether this is a suitable treatment option for you.

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Further reading