Mouth Ulcers Due to Cancer Treatment


If you are receiving radiation and chemotherapy for cancers of the head and neck, you may experience oral mucositis.

What Is Oral Mucositis?

If you are receiving radiation and chemotherapy for cancers of the head and neck, 2 of which are mouth cancer and throat cancer, you may experience oral mucositis, which can include sores and painful swelling in the mouth.

Oral mucositis can hinder eating and drinking, leading to issues with nutrition, dehydration, and weight loss. These issues may become severe, resulting in hospitalization and the use of intravenous fluids or feeding tubes. Serious adverse effects in the mouth can delay, or even stop, cancer treatment.

What Causes Mouth Sores?

Chemotherapy and radiation are meant to kill rapidly growing cancer cells. Because the cells that line the inside of the mouth also divide and grow rapidly, noncancerous, healthy cells can also be damaged by chemotherapy and radiation, which can lead to sores and infections.

Before Treatment

Although mouth sores cannot always be prevented, your health care provider may make the following recommendations:

  • Visit your dentist to take care of dental issues before beginning cancer treatment.
  • Take antiviral medications to prevent recurring mouth sores due to herpes simplex virus during cancer treatment.
  • Brush frequently with a softbristle toothbrush and fluoridated toothpaste.
  • Gently floss daily.
  • Avoid toothpastes with whitening agents.
  • Use a salt water rinse after meals and at bedtime to remove debris and keep oral tissue moist and clean.
  • Quit smoking.
  • Drink plenty of water and eat a diet rich in fruits and vegetables.
  • Avoid alcohol and irritating foods such as crunchy, salty, acidic, or spicy foods.

Depending on the type of cancer you have and the treatments you are receiving, your health care provider may recommend other techniques for reducing your risk of mouth sores.

Signs and Symptoms

Tell your health care provider if you develop any of these signs and symptoms of mouth sores:

  • Red, shiny, or swollen areas inside the mouth or on the gums
  • Sores in the mouth, on the gums, or on/under the tongue
  • A white or yellow film anywhere in the mouth
  • Blood, white patches, pus, or increased mucus in the mouth
  • Soreness or pain in mouth or throat
  • Feeling of dryness, mild burning, or pain when eating hot and cold foods

Care During Treatment

Care of mucositis during chemotherapy and radiation therapy centers on cleaning the mouth and relieving pain. It is important that you continue to maintain proper oral hygiene, brushing your teeth with a soft-bristle toothbrush every 4 hours and at bedtime. Floss gently once a day or use a water flosser on a low setting.

Mouth Rinses

To maintain oral hygiene and comfort, rinse your mouth 5 or 6 times daily for 1 to 2 minutes each time using a nonmedicated salt water rinse. Rinse, swish, and spit a mixture of 1 teaspoon of table salt in 1 L (32 oz) of water (to make 0.9% sodium chloride), with or without 1 to 2 tablespoons of sodium bicarbonate. Do not use rinses that have alcohol in them. If salt water rinses are not adequate, OTC antacid liquids (eg, Amphojel) or film-forming products (Zilactin) can be used.

Oral Protectants

Your health care provider can also prescribe oral protectants or coating agents that form a film or protective barrier to minimize mouth pain and allow you to eat and drink. These products, although often more convenient than OTC products, tend to be more costly. After application, most oral protectants require an extended wait time before eating and drinking. Examples include Episil, Caphosol, Gelclair, and MuGard.

Treating the Pain

Topical pain medications, including topical lidocaine, 0.5% doxepin mouth rinse, or a diphenhydramine mouth rinse, may be prescribed. Some health care providers will also prescribe a compounded medication known as “Magic Mouthwash” to help alleviate the pain of oral mucositis. There are many recipes, but most contain at least these 4 ingredients: a local anesthetic/ pain reliever, an antihistamine, an antacid (to enhance coating of the ingredients on the mouth), and an antibiotic or antifungal medication.

These mouthwashes may or may not be effective for oral mucositis; further research is necessary. Some patients, however, have found relief with a combination of lidocaine (for numbing), diphenhydramine, Maalox (to help coat the mouth), and Nystatin (an antifungal). If topical pain relievers do not provide enough relief, an alcohol-free morphine solution, transdermal fentanyl patch, or other narcotic pain-reliever medications can be prescribed.

How Long Will Mouth Sores Last?

With chemotherapy, mucositis heals by itself when there is no infection. Healing usually takes 2 to 4 weeks. Mucositis caused by radiation therapy lasts longer, usually 6 to 8 weeks, depending on the length of your radiation treatment.

The experience is different for every patient. Whereas you may have certain adverse effects in your mouth from head and neck radiation or chemotherapy, another patient may have different problems. Some problems go away after treatment, while others may last a long time or never go away.

Beth Bolt, RPh, is a clinical pharmacist and medical editor residing in northern California.


  • Mucositis. The Oral Cancer Foundation website. Accessed July 13, 2015.
  • Oral mucositis. Medline Plus website. Updated May 7, 2014. Accessed July 13, 2015.

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