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This information was reviewed and approved by Jeffrey Kern, MD, Bronwyn Long, DNP, MBA, ACHPN, AOCNS, ACNS-BC, Laurie L. Carr, MD (10/1/2019).

Mouth sores (mucositis) can be caused by chemotherapy and radiation therapy given to treat lung cancer.

Mucositis is the inflammation of mucous membranes from your mouth to your esophagus, stomach, intestines and anus. Chemotherapy and radiation therapy target rapidly dividing lung cancer cells, but can affect other rapidly dividing cells, such as those in your mucous membranes. 

Mild mucositis can feel like a sunburn in your mouth, heartburn, abdominal and rectal pain, and pain when having a bowel movement. People with severe mucositis have open sores in their mouths and along their GI tract, making it difficult to eat, talk, chew and swallow, or have a bowel movement. Bacteria can invade the open sores, causing infection. The pain from mucositis while eating and swallowing may decrease your appetite or desire to eat, which can have a poor effect on your overall health. Painful bowel movements can lead to constipation and reduced appetite, interfering with your desire to eat.

If you become too run-down or have persistent difficulty with mouth sores, your chemotherapy treatment may be delayed, or the dose of medication may be reduced. Mucositis tends to resolve in two to four weeks with good mouth care and medications.

What to Do with Mucositis

  • Rinse your mouth/gargle three to four (or more) times daily with ½ teaspoon salt and ½ teaspoon baking soda mixed in warm water. Begin the night before your chemotherapy treatment.

  • Drink 8 eight-ounce glasses of water daily. Purified or deionized water can reduce irritation.

  • Drink sports drinks with electrolytes to stay hydrated.

  • Drink protein drinks to help support your nutrition.

  • Drink fruit smoothies made with yogurt and fresh fruit.

  • Eat soft foods for comfort: ice cream, popsicles, milkshakes, pudding, yogurt, peanut or other nut butters, Jell-O, mashed potatoes, bananas, applesauce, scrambled eggs and oatmeal.

  • Eat foods high in protein to help promote healing.

  • Use lip balm (moisturizing, no menthol) for dry lips.

  • Use a soft toothbrush. Replace it often.

  • Floss gently to avoid irritating your gums.

  • If you wear dentures, use them for meals only; let your gums rest between meals to reduce irritation.

  • You may use a dental water flosser.

  • Contact your provider if your mucositis does not respond to these self-care tips. You may be prescribed medications or mouthwashes to help relieve discomfort.


What Not to Do with Muscositis


  • Very hot and very cold foods and beverages

  • Food and drink that can irritate tissues: citrus fruits and juices; tomatoes; and spicy or salty foods

  • All forms of alcohol, caffeine and nicotine, because these irritate and dry tissues

  • Foods high in sugar, which can make it easier for bacteria to grow

  • Breathing through your mouth

  • Rinsing with mouthwash that contains alcohol

  • Using lemon glycerin mouth swabs

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