Risk Factors Diarrhea may be caused by a temporary problem like an infection or a chronic problem like an intestinal disease. Several types of bacteria, consumed through contaminated food or water, can cause diarrhea. Common culprits include Campylobacter, Salmonella, Shigella, and Escherichia coli. Many viruses cause diarrhea, including rotavirus, Norwalk virus, cytomegalovirus, herpes simplex virus, and viral hepatitis. Some people are unable to digest a component of food, such as lactose, the sugar found in milk.
Parasites can enter the body through food or water and settle in the digestive system.
Parasites that cause diarrhea include Giardia lamblia, Entamoeba histolytica, and Cryptosporidium. Reaction to medicines, such as antibiotics, blood pressure medications, and antacids containing magnesium. Intestinal diseases, like inflammatory bowel disease or celiac disease. Functional bowel disorders, such as irritable bowel syndrome , in which the intestines do not work normally. Some people develop diarrhea after stomach surgery or removal of the gallbladder.