What Is Mucositis?

Written by Shawna Seed
Medically Reviewed by Laura J. Martin, MD on July 11, 2025
7 min read

Mucositis is the breakdown of mucous membranes in your gastrointestinal tract, the passageway that spans from your mouth to your anus. Cancer treatment often causes it. When you have mucositis, GI tract tissue can become inflamed, and you might get painful open sores. It also puts you at risk of infection in those mucous tissues. 

It can affect any part of your digestive tract, but your mouth may be the most likely place for problems to crop up. When it affects your mouth or esophagus, it’s called oral mucositis.

The lining of your GI tract is made up of a type of cells called epithelial cells, which divide quickly. Cancer treatments target rapidly dividing cells, but those treatments can also damage healthy cells.

The type of cancer you have can play a role in whether you get mucositis. People who have radiation to the head and neck are at high risk, says Ryan Huey, MD, a gastrointestinal oncologist at the University of Texas MD Anderson Cancer Center.

What type of cancer treatments can cause mucositis?

Any treatment that targets quickly dividing cells can cause mucositis. These include: 

  • Chemotherapy
  • Radiation 
  • Some targeted therapy drugs
  • Stem cell transplants

“Certain chemotherapy drugs can put patients at higher risk of developing mucositis,” Huey says. “These drugs are often used in patients who undergo stem cell transplants but can also be seen in a variety of cancers, including breast cancer, lung cancer, colon cancer, and others.”

Risk factors for mucositis

Certain things make you more likely to get mucositis during cancer treatment. They include:

  • Not taking good care of your teeth and gums
  • Using tobacco (including chewing tobacco)
  • Drinking alcohol
  • Drinking too little water
  • Having another condition such as HIV or diabetes
  • Previous cancer treatment
  • Having a low body mass index (BMI)
  • Chronic irritation from dentures or crowns that don’t fit well
  • Dry mouth, which can be caused by aging, your cancer treatment, and some medications

There’s some evidence that women and younger people are more likely to get mucositis, too.

Mucositis causes inflammation. That leads to redness, swelling, pain, and heat. 

Symptoms of oral mucositis

Here are some signs you might have oral mucositis: 

  • Gums or mouth tissues are red, swollen, or shiny 
  • Bleeding in your mouth
  • Sores on your mouth, your tongue, or gums 
  • Pain in your mouth, throat, or both
  • Trouble talking or swallowing 
  • Pain, dryness, or a burning feeling when you eat
  • Soft white patches in your mouth or on your tongue 
  • Pus in your mouth or on your tongue
  • Thick mucus or saliva in your mouth 

Symptoms of mucositis in the gut

Mucositis further down in your digestive tract can cause these symptoms: 

  • Belly pain 
  • Redness or swelling in the lining of your digestive tract (erythematous mucosa)
  • Nausea and throwing up
  • Diarrhea 
  • Pain when you poop
  • Blood or mucus in your poop

Because mucositis is such a common side effect of cancer treatment, your health care team will probably be on the lookout for it.

If your doctors suspect oral mucositis, they may take a look at your mouth to better understand your symptoms and how serious they are. They’ll also check for any signs of infection.

If your doctors think mucositis is affecting the lower parts of your GI tract, you might need imaging tests. You may need to have blood tested to rule out bacterial or fungal infections.

Your health care team will describe how serious your mucositis is by assigning it a grade. Doctors use a few different rating systems. One of them, developed by the National Cancer Institute (NCI), is the Common Terminology Criteria for Adverse Events, or CTCAE. It assigns a number between 1 and 5, with 5 meaning death related to mucositis. (While the condition isn’t fatal on its own, it can cause complications like infections and inability to eat or drink.)

There are two parts to the NCI grading. One, called the functional scale, is based on your symptoms. The second, the clinical scale, is based on what your doctor sees.

Grades in the functional evaluation include:

  • Grade 1: You have no symptoms or only mild ones, and you can eat normally. 
  • Grade 2: You have pain or sores that force you to change your diet.
  • Grade 3: You have serious pain that makes it hard to eat and drink.
  • Grade 4: Your mucositis causes life-threatening issues.

Grades in the clinical evaluation include:

  • Grade 1: You have mucosal erythema, where your mucosal tissue is red. 
  • Grade 2: You have open sores (ulcers) or raised white areas called pseudomembranes.
  • Grade 3: Your mouth ulcers or pseudomembranes turn into larger sore areas, which can bleed.
  • Grade 4: The tissue begins to die, you may bleed more, and your symptoms become life-threatening.

The World Health Organization, or WHO, uses a 0-4 scale to grade mucositis:

  • Grade 0: You have no symptoms.
  • Grade 1: You have redness and soreness.
  • Grade 2: You have some ulcers but can eat normally. 
  • Grade 3: You need a liquid diet because of the ulcers. 
  • Grade 4: The ulcers prevent you from taking in anything by mouth.

Another measurement tool is called the Oral Mucositis Assessment Scale, or OMAS. It measures redness and sores at nine different spots in your mouth.

There’s no treatment that can cure mucositis. Once you finish your cancer treatment, it should heal on its own. In the meantime, your health care team can help you manage your symptoms. 

“Always talk to your clinical team for guidance, since mucositis can be caused by multiple factors, and they can help to tailor the appropriate treatment strategy for you,” Huey says.

Treating oral mucositis

To help you manage your pain, your doctor might suggest:

  • Topical anesthetics that numb sore areas
  • Anti-inflammatory drugs such as steroids
  • Over-the-counter pain relievers such as acetaminophen
  • Prescription pain medication 
  • A “GI cocktail,” which has an antacid, an anesthetic, and a medicine to kill fungal infections 
  • “Magic mouthwash,” which usually contains an anesthetic, an antacid, an antihistamine, and possibly steroids or other ingredients 
  • Photobiomodulation therapy, a type of light therapy 

Treating gut mucositis

How your doctor treats your gut mucositis depends on your symptoms. Possibilities include:

  • Anti-nausea drugs
  • Drugs to limit stomach acid and numb pain
  • Drugs to relax your gut if you have cramping 
  • Drugs to treat diarrhea
  • Creams to soothe a sore anus

Both oral and gut mucositis can lead to complications such as dehydration, poor nutrition, and infection. If you develop these conditions, your treatment might include:

  • IV fluids
  • Tube feeding that puts nutrients straight into your gut, bypassing your mouth 
  • Antibiotics

If your mucositis is serious, you might have to reduce your level of cancer treatment or delay it. 

If you’re getting chemotherapy, mucositis may start around five to 10 days after you get chemo drugs. It usually lasts a week or two. It’ll get better as your white blood cell count improves.

If you’re getting radiation, mucositis usually begins one to three weeks after you start treatment. It usually lasts as long as you’re undergoing radiation. Your symptoms should start to get better four to six weeks after your treatment is over. 

Before you start your cancer treatment, see a dentist familiar with radiation and chemotherapy issues. If you need dental work — a filling, for example — it should be finished four to six weeks before you start treatment. If you wear dentures, have the dentist make sure they fit well.

Doctors are studying medicines that might prevent mucositis or make it less serious. They include:

  • Palifermin, a synthetic version of keratinocyte growth factor (KGF), which your body makes to protect and repair the cells that line your mouth and GI tract
  • Oral gels that coat and protect your mouth before radiation 
  • Amifostine, which you can take before radiation for head and neck cancers to lessen mucositis 

Taking good care of your teeth and gums may help you avoid mucositis or keep it from getting worse. Steps you can take include: 

  • Brushing regularly — three or four times daily — with a soft-bristle toothbrush and mild toothpaste
  • Rinsing your mouth five to six times a day with salt water or a mixture of salt water and baking soda
  • Eating soft, mild foods
  • Taking in extra fluids, which can include sucking on ice chips or using an artificial saliva product

There are a few things to avoid, such as: 

  • Toothpicks, which can hurt your mouth 
  • Whitening toothpastes
  • Mouthwashes that contain alcohol, which can dry your mouth
  • Letting dentures irritate your mouth (Take them out occasionally to expose your gums to air.)

In terms of diet, focus on: 

  • Protein, which helps your body build strength 
  • Cold items such as ice pops, ice cream, and ice chips
  • Mild foods, such as yogurt or smoothies
  • Soft foods, such as potatoes, pasta in white sauce, and stews
  • Gravies and sauces that can make food easier to eat

You may want to drink through a straw to protect sore spots in your mouth. 

Mucositis is a common side effect of cancer treatment, especially cancers of the head and neck. It can affect any part of the GI tract, from your mouth to your anus. Symptoms include redness, swelling, and sores in your mouth. You might have nausea, vomiting, diarrhea, or stomach cramps if your gut is affected. You and your doctor can take steps to manage symptoms and control pain. 

Here are some commonly asked questions about mucositis.

What is the fastest way to cure mucositis?

There’s no cure for mucositis, but it usually heals on its own after you finish cancer treatment. In the meantime, your doctor can prescribe medications to help you manage your symptoms.

Is mucositis contagious?

No, mucositis isn’t contagious. It’s an inflammatory condition. It’s not caused by an infection and you can’t spread it to others. 

What foods should be avoided with mucositis?

Try to limit or avoid: 

  • Acidic foods, such as citrus, tomatoes, and peppers
  • Spicy foods
  • Crusty or hard-to-chew foods, such as chips, pretzels, and hard bread
  • Alcohol and carbonated drinks
  • Sugary snacks 

How do I get rid of mucus in my throat after radiation?

Drinking plenty of water can help thin your mucus. A humidifier can also help loosen thick mucus.