Mouth Sores or Sore Throat

Mouth sores are like little cuts or ulcers in the mouth. The sores may be very red, or may have small white patches in the middle. They may bleed or become infected. They can appear 1 to 2 weeks after some kinds of chemo. They can also be caused by radiation treatments to the head and neck area, infection, dehydration, poor mouth care, oxygen therapy, alcohol or tobacco use, not getting enough vitamins, or lack of protein. Healing may take 2 to 4 weeks. Mouth sores can be very painful and lead to dehydrationpoor eating, and weight loss.

Ask your doctor for medicine to relieve the pain or discomfort when you chew or swallow.

If you have these problems, eating soft, bland foods and lukewarm or cool foods can be soothing. On the other hand, foods that are coarse, dry, or scratchy may make you feel worse. You may also find that tart, salty, or acidic fruits and juices; alcohol; and spicy foods are irritating.

What to look for

  • Inside of mouth and gums look red, shiny, or swollen
  • Small ulcers or sores in mouth, on gums, or on or under tongue
  • A white or yellow film in the mouth or on the tongue
  • Blood in the mouth
  • Soft, whitish patches or pus in the mouth
  • Increased mucus in the mouth
  • Soreness or pain in the mouth or throat
  • Feeling of dryness, mild burning, or pain when eating hot and cold foods

What the patient can do

Check your mouth twice a day using a small flashlight and a padded Popsicle stick. If you wear dentures, take them out before you check your mouth. Tell your cancer team if your mouth looks or feels different or if you notice changes in how things taste.

Follow this plan for mouth care 30 minutes after eating and every 4 hours while you’re awake, or at least twice a day unless you’ve been given other instructions:

  • Brush your teeth using a soft nylon bristle toothbrush. To soften the bristles even more, soak the brush in hot water before brushing and rinse it with hot water during brushing. If the toothbrush hurts, use a Popsicle stick with gauze wrapped around it. Or get soft foam mouth swabs to clean your teeth. (You can buy these at a drugstore.)
  • Rinse toothbrush well in hot water after use and store in a cool, dry place.
  • Use a non-abrasive toothpaste that contains fluoride. Note that whitening toothpastes may contain hydrogen peroxide, which can irritate sore mouths.
  • Remove and clean your dentures between meals on a regular time schedule. If you have sores under your dentures, leave your dentures out between meals and at night.
  • Clean dentures well between uses, and store them in an anti-bacterial soak. If your dentures fit poorly, do not use them during treatment.
  • Gently rinse your mouth before and after meals and at bedtime with one of the following solutions (Stir or shake the solution well, then swish it around and gently gargle, then spit it out.):
    1 teaspoon baking soda mixed with
    2 cups water
    1 teaspoon salt and
    1 teaspoon baking soda mixed with
    1 quart water
  • Avoid store-bought mouthwashes, which often contain alcohol or other irritants.
  • If you normally floss, keep flossing at least once a day unless you’re told not to do so. Tell your cancer team if this causes bleeding or other problems. If you don’t usually floss, ask before you start.
  • Keep your lips moist with petroleum jelly, a mild lip balm, or cocoa butter.
  • Drink at least 2 to 3 quarts of fluids each day, if your cancer team approves.
  • To promote healing, ask about using Maalox® or Milk of Magnesia®. You can use these products to help sores by allowing them to settle and separate, pouring the liquid off the top of the solution, and then swabbing the pasty part onto the sore area with a cotton swab. Rinse your mouth with water after letting the paste sit for 15 to 20 minutes.
  • If mouth pain is severe or makes it hard to eat, ask about medicine that can be swished 15 to 20 minutes before meals or painted on a painful sore with a cotton swab before meals. If this doesn’t work, you may need something stronger. Ask about other medicines to relieve pain.
  • Eat chilled foods and fluids (such as Popsicles, ice chips, frozen yogurt, sherbet, or ice cream).
  • Eat soft, moist foods that are easy to swallow.
  • Use a straw
  • Eat small, frequent meals of bland, moist, non-spicy foods. Avoid raw vegetables and fruits, and other hard, dry, or crusty foods, such as chips or pretzels.
  • Don’t eat very salty, spicy, or sugary foods.
  • Avoid acidic fruits and juices, such as tomato, orange, grapefruit, lime, or lemon.
  • Avoid fizzy drinks, alcohol, and tobacco.
  • Create a pleasant mealtime atmosphere.

What caregivers can do

  • Use a flashlight to check the patient’s mouth for red areas or white patches, which often become sores. If the patient wears dentures, remove them before looking.
  • Offer liquids with a straw, which may help bypass the sores in the mouth.
  • Offer soft foods. Mash or puree foods in a blender to make them easier to eat.
  • Try coating mouth sores with Anbesol® or Orajel® before meals to numb them during eating.
  • Offer pain medicines 30 minutes before mealtime.

Call the cancer team if the patient:

  • Has redness or shininess in their mouth that lasts for more than 48 hours
  • Has bleeding gums
  • Notices any type of “cut” or sore in the mouth
  • Has a temperature of 100.5° F or higher when taken by mouth
  • Has white patches on the tongue or inside the mouth
  • Has taken in little food or fluid for 2 days
  • Can’t take medicines because of mouth sores

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Fauci AS, Braunwald E, Kasper DL, et al (Eds). Harrison’s Principles of Internal Medicine, 17th ed. New York: McGraw-Hill Medical, 2008.

Camp-Sorrell D, Hawkins RA. Clinical Manual for the Oncology Advanced Practice Nurse, Second Ed. Pittsburgh: Oncology Nursing Society, 2006.

Cope DG, Reb AM. An Evidence-Based Approach to the Treatment and Care of the Older Adult with Cancer. Pittsburgh: Oncology Nursing Society, 2006.

Eldridge B, and Hamilton KK, Editors, Management of Nutrition Impact Symptoms in Cancer and Educational Handouts. Chicago, IL: American Dietetic Association; 2004.

Houts PS, Bucher JA. Caregiving, Revised ed. Atlanta: American Cancer Society, 2003.

Kaplan M. Understanding and Managing Oncologic Emergencies: A Resource for Nurses. Pittsburgh: Oncology Nursing Society, 2006.

Kuebler KK, Berry PH, Heidrich DE. End-of-Life Care: Clinical Practice Guidelines. Philadelphia: W.B. Saunders Co. 2002.

National Comprehensive Cancer Network. Palliative Care. Version 1.2015. Accessed at on March 19, 2015.

Oncology Nursing Society. Cancer Symptoms. Accessed at on April 3, 2013.

Ripamonti C, Bruera E. Gastrointestinal Symptoms in Advanced Cancer Patients. New York: Oxford University Press, 2002.

Varricchio CG. A Cancer Source Book for Nurses, 8th ed. Sudbury, MA: Jones and Bartlett, 2004.

Yarbro CH, Frogge MH, Goodman M. Cancer Symptom Management, 3rd ed. Sudbury, MA: Jones and Bartlett, 2004.

Last Medical Review: June 8, 2015 Last Revised: July 29, 2019

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