Mouth problems

Some cancer treatment can cause mouth problems. Your healthcare team can tell you how to look after your mouth during and after treatment.

How cancer treatment can affect your mouth

Some cancer treatments can damage the cells that line your mouth or throat. These treatments include chemotherapy, radiotherapy, targeted therapies and immunotherapies. Your specialist nurse and doctor will talk to you about how to care for your mouth during and after treatment. Tell them if your mouth is sore.

Some possible mouth problems

We have listed some of the possible problems cancer treatments may cause and ways to help manage them:

Sore mouth and throat (mucositis)

Your mouth and throat may become sore during and after cancer treatment. You may develop mouth ulcers.

If you are having radiotherapy to the head and neck area, your mouth and throat are likely to become sore within 2 weeks of starting treatment. You may also have difficulty swallowing. Side effects of radiotherapy may continue for 7 to 10 days after treatment ends. After this they usually slowly improve. Most people notice an improvement in their side effects 6 to 8 weeks after radiotherapy has finished.

Your healthcare team will tell you how your treatment can affect your mouth. Tell your nurse or doctor if your mouth is sore. They will check for problems such as infection or ulcers and may recommend mouthwashes, painkillers or other treatments to help.

Regularly rinsing your mouth with a salt water (saline) mouthwash or one prescribed by your nurse or doctor can help. If it is too sore to brush your teeth, they may suggest gently cleaning around teeth and gums with a gauze swab soaked in saline mouthwash.

Your doctor or nurse may prescribe a gel, spray or mouthwash that forms a protective coating over sore areas in the mouth. You apply gels such as Orabase® and sprays like Episil® directly on sore areas in your mouth. Your nurse may advise you to use a mouthwash, such as Caphosol® or Gelclair®, several times a day and before eating. Or they may prescribe a mouthwash that contains a local anaesthetic to numb your mouth. This can make it easier to eat and drink.

Painkillers can help ease mouth soreness. It is important to take painkillers regularly as prescribed. This keeps a constant level of painkiller in your blood so that it works more effectively for you.

If you find swallowing pills difficult, there are liquid and soluble painkillers. If mild painkillers like paracetamol do not control the pain, tell your doctor. They may prescribe something stronger, such as codeine with paracetamol (co-codamol). For severe mouth pain, doctors may prescribe strong painkillers such as morphine.

Mouth infection

The most common mouth infection is called thrush. Thrush usually appears as white patches, or a white coating, over the lining of the mouth and tongue. It can also cause bad breath. Tell your doctor or nurse if you have any of these symptoms. It is treated with anti-fungal drugs. These can be tablets (fluconazole) or a liquid you put on your tongue (nystatin). Doctors sometimes prescribe these treatments to prevent thrush.

Rarely, an infection in your mouth can enter your bloodstream and make you very unwell. If you feel unwell or have a high temperature contact the hospital straight away. A high temperature may be over 37.5°C, depending on the advice of your hospital team.

Changes in your taste

Chemotherapy may affect your taste. You may get a bitter or metal taste in your mouth. Sucking sugar-free sweets may help with this. Some foods may taste different or have no taste. Try different foods to find out what tastes best to you. Taste changes usually get better after treatment finishes. Your nurse can give you more advice.

Radiotherapy to your head and neck affects your sense of taste. Some people lose their sense of taste completely or find that everything tastes the same (usually metallic or salty). Although your sense of taste should recover, it may take many months for this to happen.

Dry mouth

Chemotherapy can cause a dry mouth. Radiotherapy to the head and neck area can affect the salivary glands. So you may not make as much saliva as before. Your mouth and throat may become dry. This can make eating and speaking more difficult.

If your mouth is dry, the following may help:

  • Take sips of water often.
  • Moisten foods with sauces and gravies.
  • Suck on sweets, ice cubes or an ice lolly.
  • Keep your lips moist by using Vaseline® or a lip balm. If you are having radiotherapy to your head or neck, check with your radiotherapy team or specialist nurse before using any products on your lips.

You may be prescribed artificial saliva to help your mouth feel more comfortable. It comes in different forms, such as sprays, gels, lozenges and pastilles. You may have to try different types to find one that works for you.

Thick, sticky saliva (mucus)

Radiotherapy to your head or neck can change your saliva. It can make it thicker, stringy and sticky, like mucus. The mucus does not flow as well as normal saliva, so it may build up in the mouth and throat

You may feel the need to spit frequently to get rid of the mucus build-up, so it is a good idea to keep tissues with you. Rinsing your mouth regularly can help. Using a sodium bicarbonate mouthwash every 3 to 4 hours may help clear thick saliva. To make the mouthwash, add 1 tablespoon of sodium bicarbonate to 900ml of cooled, boiled water. Rinse the mouthwash around your mouth and then spit it out. You should make a fresh mouthwash each day. Or your specialist nurse can give you advice on the type of mouth rinse that is best for you.

Sometimes a build-up of mucus can cause coughing, especially at night. Your nurse or doctor may prescribe a nebuliser. This is a small machine that changes liquid medicine into a fine mist or spray, to help to loosen the mucus. If your sleep is disturbed by coughing, using a nebuliser before bed may help.

Changes in your saliva may get better within about 8 weeks of radiotherapy ending. But sometimes it continues for several months or longer. If the mucus continues, tell your cancer specialist or nurse. They may be able to prescribe medicines to reduce the amount you make.

Problems chewing or swallowing

Radiotherapy to the head or neck area can cause pain and swelling in the mouth or throat. This can make it painful to chew or swallow. An infection in your mouth or throat can also make chewing and swallowing uncomfortable.

Let your doctor or dietitian know if you are having any problems. If drinking makes you cough, tell your doctor or specialist nurse as soon as possible. A speech and language therapist (SLT) can give you advice about swallowing problems.

We have more about coping if you have problems chewing or swallowing.

Looking after your mouth

Keeping your mouth as clean as possible during your treatment will help to prevent or reduce side effects in your mouth.

Many hospitals have their own mouth care guidelines for people having different types of treatment. They will tell you how to keep your mouth clean during and after treatment. They may also advise you to see your dentist before you start treatment. Below are some general tips for how to look after your mouth.


Mouthwashes can be very soothing, but many of the ones available in chemists or shops may be too strong for you. Salt-water mouthwashes are just as effective at reducing soreness if it is not too severe.

You can make this by adding a teaspoon of salt to cold or warm water. Rinse this around your mouth and then rinse with cold or warm water. Or your doctor can prescribe an anaesthetic gel or mouthwash instead.


Use fluoride toothpaste to clean your teeth. If your usual brand irritates your mouth, or if your mouth is sore, choose a mild, non-foaming toothpaste. Some people find children’s toothpaste less irritating. You can ask your nurse if there is one they recommend.


Use a children’s soft toothbrush to clean your teeth gently. Avoid using toothpicks when cleaning your teeth. If you want to use dental floss, check with your doctor or specialist nurse first. If you have a low platelet count, flossing can make your gums bleed.


If you wear dentures, soak them in a denture-cleaning solution overnight. Leave them out for as long as you can during the day to prevent them rubbing against your gums.

If you are having radiotherapy to the jaw area, you may be advised to keep your dentures in as much as possible during the day to help maintain the shape of your gums. But if your mouth is very sore, it may be more comfortable to leave your dentures out.

Cleaning your tongue

If your tongue is ‘coated’, it may make your food taste unpleasant and might put you off eating. You can clean your tongue with a bicarbonate of soda solution. Use 1 teaspoon of bicarbonate of soda (you can get this from your chemist) dissolved in a pint (570ml) of warm water. Clean your tongue with a soft toothbrush or gauze dipped in the solution. Check with your clinical nurse specialist for more advice.

Eating and drinking if you have mouth problems

Some people can find drinking fluids difficult if they have a very sore mouth. If this happens you may need to be admitted so you can have fluids through a drip (IV infusion).

The following tips may be helpful:

  • Drink plenty of fluids, especially water. If you find that fresh fruit juices sting your mouth, try less acidic juices instead, such as peach or pear nectar, or blackcurrant or rosehip syrup. You could try freezing them in an ice-cube tray – sucking on the ice cubes can soothe your mouth.
  • Try milk or milk-based drinks, such as malted drinks, milkshakes and hot chocolate.
  • Cold foods and drinks may be more soothing. Try adding crushed ice to drinks and eating ice cream or soft, milk jellies.
  • Very hot or very cold drinks may irritate a sore mouth. Some people find drinks that are lukewarm or at room temperature more soothing.
  • Try drinking through a straw.

If you have problems eating

Tell your doctor or nurse if you are not managing to eat. They may refer you to a dietitian for extra support and advice.

There are also some eating tips you can try if you are finding eating difficult:

  • Avoid salty or spicy food.
  • Avoid rough-textured food like toast or raw vegetables.
  • Keep your food moist by adding sauces and gravies.
  • You may find that taking painkillers before meals can help you swallow more easily.
  • Chewing gum can sometimes stimulate the production of saliva.

We have more information about eating problems and what might help.