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What it is

Diarrhea is frequent bowel movements which may be soft, formed, loose, or watery. Diarrhea can occur at any time during radiation therapy.


Why it occurs

Radiation therapy to the pelvis, stomach, and abdomen can cause diarrhea. People get diarrhea because radiation harms the healthy cells in the large and small bowels. These areas are very sensitive to the amount of radiation needed to treat cancer.


Ways to manage it

When you have diarrhea:

  • Drink 8 to 12 cups of clear liquid per day. See  "Clear Liquids"  for ideas of drinks and foods that are clear liquids.

    If you drink liquids that are high in sugar (such as fruit juice, sweetened iced tea, Kool-Aid®, or Hi-C®) ask your nurse or dietitian if you should mix them with water.


Radiation to the shaded area may cause diarrhea.

  • Eat many small meals and snacks. For instance, eat five or six small meals and snacks rather than three large meals.


  • Eat foods that are easy on the stomach (which means foods that are low in fiber, fat, and lactose). See "Foods and Drinks That Are Easy on the Stomach" for other ideas of foods that are easy on the stomach. If your diarrhea is severe, your doctor or nurse may suggest the BRAT diet, which stands for bananas, rice, applesauce, and toast.   


  • Take care of your rectal area. Instead of toilet paper, use a baby wipe or squirt of water from a spray bottle to clean yourself after bowel movements. Also, ask your nurse about taking sitz baths, which are warm-water baths taken in a sitting position that covers only the hips and buttocks. Be sure to tell your doctor or nurse if your rectal area gets sore.

  • Stay away from:

    • Milk and dairy foods, such as ice cream, sour cream, and cheese
    • Spicy foods, such as hot sauce, salsa, chili, and curry dishes
    • Foods or drinks with caffeine, such as regular coffee, black tea, soda, and chocolate
    • Foods or drinks that cause gas, such as cooked dried beans, cabbage, broccoli, soy milk, and other soy products
    • Foods that are high in fiber, such as raw fruits and vegetables, cooked dried beans, and whole wheat breads and cereals
    • Fried or greasy foods
    • Food from fast food restaurants

  • Talk to your doctor or nurse. Tell them if you are having diarrhea. He or she will suggest ways to manage it. He or she may also suggest taking medicine, such as Imodium®.


To learn more about dealing with diarrhea during cancer treatment, see Eating Hints, a book from the National Cancer Institute. You can get a free copy at or 1-800-4-CANCER.