Mouth problems

Older man with a sore mouth

Drug therapies like chemotherapy and targeted therapies and radiotherapy to the head and neck area can affect your mouth in different ways:

Sore / sensitive mouth 

Your mouth or gums may get sore. You may also get little ulcers on your tongue, gums and inside your cheeks (mucositis). Your mouth may be more sensitive to hot, cold, acidic or spicy food as well.

How is it treated?

There are many mouthwashes, gels and medications such as painkillers, antiseptic or local anaesthetic gels or lozenges, which your doctor can prescribe for you. If you have an infection your doctor may prescribe an antibiotic. 

What can I do?

  • Keep your teeth, gums and mouth very clean, as this will help to control the soreness and reduce the risk of a mouth or throat infection.
  • Brush your teeth regularly with a small, soft toothbrush and mild fluoride toothpaste, especially after meals and before bedtime. It may help to soften the brush in warm water before brushing. 
  • Use a mouthwash regularly if prescribed for you. Only use mouthwashes recommended by your dentist, radiation therapist or nurse. Some mouthwashes contain alcohol and are too harsh. You can also make your own using 1 teaspoon of baking soda (sodium bicarbonate) and 1 teaspoon of salt dissolved in 1 pint / half a litre of warm water.
  • Avoid toothpicks
  • If you have dentures, remove them every night and if your gums are sore.
  •  Take sips of fluids like water or milk often. Drink through a straw if your mouth is painful.
  • Use a lip balm to keep your lips moist.
  • Visit your dentist regularly. They can give you advice about caring for your mouth and special mouthwashes.
  • Eat soft, moist food like omelettes, scrambled eggs, mashed potatoes, cream soups, natural yogurt, milkshakes, stews, puddings.

  • Moisten your food with sauces or gravies.

  • Purée or liquidise foods in a blender to make them easier to swallow. For example, try soups or smoothies.

  • Take care with the following as they can make a sore mouth or throat worse:

    – Pickled, salty or spicy foods

    – Rough food, like crispy bread, dry toast or raw vegetables

    – Alcohol and tobacco

    – Citrus juices, like orange, lemon, lime, grapefruit or pineapple

    – Mouthwashes that contain alcohol, or acidic ones.

Dry mouth (xerostomia – “zero-sto-mee-a”) 

You may notice that your mouth and throat feel dry all the time. This is because treatment can cause the salivary glands to make less saliva (spit) than usual.

You may also find that saliva can become thick and stringy after radiotherapy, making swallowing and speech a little difficult too. The dryness may improve with time but can be permanent. 

What can I do?

  • Carry a water bottle with you and drink water throughout the day to keep your mouth moist.
  • Use sauces or gravy to make food moist and easier to swallow and avoid very dry foods like crackers.
  • Keep your lips moist with aqueous cream. 
  • Ask your doctor about artificial saliva products.
  • Sugar-free chewing gum can help to stimulate saliva.
  • Smoking can make a dry mouth worse, so try to give up or cut down. 
  • If you have green or yellow mucus, tell your doctor. He or she may want to treat you with medication.

Problems with your teeth

If your mouth is dry you will need to take special care of your teeth. They will be more at risk of decay because of the lack of saliva. Decay can happen very quickly and can cause your teeth to break.

If you are likely to develop dental problems, a dental specialist will check your progress during radiotherapy. After the course has finished, you will need to have regular dental check-ups (every 4–6 months).

What can I do?

  • Avoid sucking sugary sweets when your mouth feels dry as it increases your risk of tooth decay. It is better to use water or sugar-free chewing gum or sweets. 
  • Avoid sugary foods and look for the ‘hidden sugars’ on the labels.
  • Fluoride products can help to help prevent decay. Your doctor will give this to you. This can be in the form of a mouthwash, special toothpaste or applied in a special gum shield made by your dentist.
  • If you decide to have any dental work after radiotherapy, do tell your dentist that you have had radiotherapy. It is very important to avoid having teeth taken out (extractions) after radiotherapy, as your gums may not heal well afterwards or you may get a bone infection called osteoradionecrosis (ORN). 

Taste changes

Some cancer treatments such as some chemotherapy drugs or radiotherapy can affect the taste buds in your mouth. You may find that food tastes bland, salty, metallic or like cardboard. If this happens, you may lose interest in food.

Your normal taste should come back in the months after treatment has ended. Some people will experience some longer term taste changes.

Speak to your medical team if you have any concerns about your taste.

See our page on eating problems and weight loss for tips to help you if your taste has changed.

Voice changes: Radiotherapy can make your voice hoarse for a time. Rest your voice as much as possible and avoid smoky places. A speech and language therapist can advise you on voice exercises to help.

Sore throat 

Your throat may be red and sore. Sometimes eating food may become difficult and swallowing painful. 

Your doctor or dietitian will advise you on how to change your diet to make eating more comfortable.

You may need to be fed by a nasogastric tube or PEG tube for a short while if you’re not able to eat. 

Jaw stiffness (trismus)

Sometimes radiation to your head and neck can cause a stiffness in certain facial muscles. This is called trismus. The stiffness can prevent you opening your mouth and jaw fully. You will be shown some simple mouth-opening exercises to keep your mouth as flexible as possible. These should be done at least twice every day. 

A speech and language therapist may also provide other ways to help. For example, you can check your facial muscles by doing the ‘3 finger test’ – turn your hand sideways and see if you can open your mouth wide enough to fit 3 fingers in. You may also be advised to use an exercise device called a TheraBite®.

Osteoradionecrosis (ORN)

After radiotherapy your jaw bone can have less blood supply and not heal so well. If the bone is injured by surgery, tooth extractions or denture irritations, a condition called osteoradionecrosis (ORN) can develop. It is much better to keep your teeth in good condition and to treat any tooth decay (cavities) quickly if they occur.

If a tooth has to be taken out after radiotherapy, you should see a dentist who is used to dealing with patients who have had radiotherapy. The tooth will need to be removed carefully and extra precautions will be taken to prevent infection, such as prescribing antibiotics. 

Tell your doctor or dentist immediately if you develop any problems with your teeth or gums, or swelling, pain, heaviness or numbness of your jaw.

For more information

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