Managing a sore mouth, dry mouth or mouth infections

This information has been prepared to explain the causes, symptoms and ways to cope with a sore/dry mouth and mouth infections.

A sore mouth or dry mouth and mouth infections are common problems for people having treatment for cancer. Finding and managing symptoms early can improve a sore and dry mouth.

Sore mouth

A sore mouth is often called mucositis or less commonly, stomatitis.

The causes of sore mouth

  • Chemotherapy: A sore mouth may be an effect of some chemotherapy drugs. The cells of the mouth and digestive tract (mucosa) are sensitive to chemotherapy. Some chemotherapy drugs are more likely than others to cause this problem―check with your cancer doctor or nurse about your chemotherapy.
  • If you are having chemotherapy you are more likely to develop mouth ulcers (sore and broken areas inside the mouth) and infections in the mouth. The effects of chemotherapy on the mouth usually clear up 4 to 6 weeks after finishing treatment.
  • Radiation treatment to the head and neck.
  • Cancer in the mouth.
  • Medications, such as steroids and antibiotics, can cause mouth ulcers and/or infections.

Before starting chemotherapy any dental problems should be treated. Anyone having radiation treat­ment to the head and or neck will be checked by a dentist before radiation treatment.

Early symptoms of a sore mouth

Symptoms often include burning or redness or both, a feeling of roughness or smoothness of the gums or mouth. This may lead to a mouth ulcer. White or yellow patches inside the mouth may be a sign of fungal infections (thrush). Contact your cancer nurse or doctor as soon as you notice any symptoms.

Managing a sore mouth

Follow the instructions given to you by your cancer nurse or doctor for the care of your mouth. Don’t buy over-the-counter mouthwashes―these often have alcohol in them, which will dry your mouth.

Tips for care of your mouth and teeth

  • Use a soft toothbrush gently on your teeth and gums.
  • Wet your toothbrush in warm water to soften the bristles.
  • Use fluoride toothpaste.
  • Use baking soda mouth rinses often during the day, after food, and before going to sleep at night.

Mouthwash recipe

1 teaspoon of salt

1 teaspoon of baking soda

4 glasses water.

Mix and keep this mouthwash in the fridge.

Baking soda is a good cleanser, encourages healing and reduces tooth decay.

Managing pain

Medication to relieve pain may be needed―talk to your cancer doctor or nurse if it is a problem.


  • Avoid alcohol and tobacco.
  • Avoid spicy, salty or acidic food or drink, for example, raw tomatoes, citrus fruit and citrus juice, or very rough and coarse foods such as toast and raw vegetables.
  • Try blackcurrant or rosehip syrup, apple juice, peach or pear nectar or herbal teas.
  • Avoid very hot or very cold food.
  • Eat food with a soft or smooth texture, for example, yoghurt, milkshakes, mashed potatoes or taro, scrambled eggs, and jelly. Use a blender to purée foods.
  • Have some tins of baby food on hand for a quick snack.
  • Eat some fresh, ripe pineapple. Pineapple has an enzyme that helps clean your mouth.
  • Try to drink plenty of fluid during the day―a moist mouth is less likely to get sore.
  • Try drinking through a straw to avoid the sore areas.
  • If you wear dentures, leave them out at night (soak them in a denture cleaning solution) and for periods during the day. If you are having radiation treatment to the head and neck you will need to leave your dentures out until several weeks after treatment finishes.

Dry mouth

The causes of dry mouth

  • Radiation treatment to the head or neck or both.
  • When salivary glands are radiated, dry mouth may continue for months or years or, for some people, may always be a problem.
  • Some chemotherapy drugs can dry your mouth but this usually clears up 6 to 8 weeks after treatment finishes.
  • Other medications can cause a dry mouth.

Managing a dry mouth

  • Rinse your mouth and brush teeth and gums with a soft toothbrush after eating.
    Radiation treatment may affect the ability of your mouth to produce saliva.
  • Saliva helps to clean your mouth and prevent decay; good care of your mouth and teeth is important.
  • Tell your cancer nurse or doctor if you are vomiting or feeling sick.
  • Sip drinks with meals.
  • Add sauces or gravy to dry foods.
  • Discuss the use of drink supplements (available on prescription) with your cancer doctor or nurse or dietitian.
  • Dip biscuits in warm drinks to soften them.
  • Avoid tobacco, alcohol and over-the-counter mouthwashes. These can irritate and dry your mouth.
  • Try sugar-free gum.
  • Use a humidifier, especially at night.
  • Carry a small spray bottle filled with water to squirt into your mouth often during the day.
  • Keep lips moist with lanolin, especially at night, to prevent lip dryness, which can happen when you breath through your mouth while you sleep.
  • Suck ice chips slowly to relieve pain and as a saliva substitute (acts like it).
  • Vegetable oil in a spray bottle (to squirt into your mouth) can provide a protective coating to the lining of the mouth.

Any saliva that your mouth produces after radiation treatment may be thicker or thinner than before. Each has its difficulties. Thin saliva makes it difficult to chew and swallow some foods but mashed potato or a sauce can help. Thick, sticky saliva may be a problem too, especially on waking.


Rinsing your mouth before eating will thin saliva.

Foods to try for this problem include thin, hot cere­als or thin soups, fruit ice-blocks, warm, sugar-free lemonade, melon, blended and diluted vegetables or fruit juices.

The Cancer Society has published a booklet Dealing with Dry Mouth. You can get a copy of this booklet at your local Cancer Society or by phoning the 0800 number at the end of this Information Sheet. You can also read or listen to this booklet on the Society’s website.

Mouth infections

The causes of mouth infections

  • Mouth infections can result from irritated, painful and broken areas in the mouth lining.
  • Chemotherapy lowers your immunity (your body’s way of protecting itself), leaving you open to infection.
  • Radiation treatment to the head or neck or both can damage the lining of the mouth.

Common types of infection

  • Candida (oral thrush)
  • Herpes virus (cold sores)
  • Bacteria.

Managing a mouth infection

Signs to look for:

  • redness
  • smoothness of gums
  • white patches inside your mouth
  • a coated tongue
  • bad breath
  • a burning sensation.

If you think you have an infection talk to your cancer doctor or nurse.

Practicing good oral hygiene and avoiding mouth irritation

See suggestions for “Managing a sore mouth” and “Managing a dry mouth” above.

This information was reviewed in 2014 by the Cancer Society of New Zealand. It is reviewed every four years.

For cancer information and support phone 0800 CANCER (226 237).