Some infections, food allergies and intolerances, digestive tract problems, abdominal surgery, and long-term use of medicines can cause chronic diarrhea.
Infections
Some infections from bacteria and parasites that cause diarrhea do not go away quickly without treatment. Also, after an infection, people may have problems digesting carbohydrates such as lactose or proteins in foods such as cow’s milk, milk products, or soy NIH external link. Problems digesting carbohydrates or proteins can prolong diarrhea.
Food allergies and intolerances
Allergies to foods such as cow’s milk, soy, cereal grains, eggs, and seafood may cause chronic diarrhea.
Lactose intolerance is a common condition that may cause diarrhea after eating foods or drinking liquids that contain milk or milk products.
Fructose intolerance is a condition that may cause diarrhea after eating foods or drinking liquids that contain fructose, a sugar found in fruits, fruit juices, and honey. Fructose is added to many foods and soft drinks as a sweetener called high-fructose corn syrup.
Sugar alcohols such as sorbitol, mannitol, and xylitol may cause diarrhea in some people. Sugar-free candies and gum often include these sugar alcohols.
Digestive tract problems
Digestive tract problems that may cause chronic diarrhea include
irritable bowel syndrome and other functional gastrointestinal (GI) disorders
small intestinal bacterial overgrowth
Abdominal surgery
You may develop chronic diarrhea after abdominal surgery. Abdominal surgery is an operation on the appendix, gallbladder, large intestine, liver, pancreas, small intestine, spleen, or stomach.
Long-term use of medicines
Medicines that must be taken for a long time may cause chronic diarrhea. Some medicines, such as antibiotics, can change the normal gut flora and increase your chances of infection with Clostridioides difficile, a bacterium that can cause chronic diarrhea.