What Causes Diarrhea?
Viral infections cause most cases of diarrhea and are typically associated with mild-to-moderate symptoms with frequent, watery bowel movements, abdominal cramps, and a low-grade fever. Viral diarrhea generally lasts approximately three to seven days.
The following are the common causes of diarrhea caused by viral infections (viral gastroenteritis):
- Rotavirus is a common cause of diarrhea in infants.
- Norovirus (for example, Norwalk virus, caliciviruses) is the most common cause of epidemics of diarrhea among adults and school-age children (for example, cruise ship infection, schools, nursing homes, day care facilities, and restaurants).
- Adenovirus infections are common in all age groups.
Bacterial infections cause the more serious cases of infectious diarrhea. Typically, infection with bacteria occurs after eating contaminated food or drinks (food poisoning). Bacterial infections also cause severe symptoms, often with vomiting, fever, and severe abdominal cramps or abdominal pain. Bowel movements occur frequently and may be watery and individuals may experience "explosive diarrhea" which is a very forceful, almost violent, expulsion of loose, watery stool along with gas.
The following are examples of diarrhea caused by bacterial infections:
- In more serious cases, the stool may contain mucus, pus, or blood. Most of these infections are associated with local outbreaks of disease. Family members or others eating the same food may have similar illnesses.
- Foreign travel is a common way for a person to contract traveler's diarrhea. (Traveler's diarrhea also may be caused by unfamiliar viruses or parasites.)
- Campylobacter, salmonellae, and Shigella organisms are the most common causes of bacterial diarrhea.
- Less common causes are Escherichia coli (commonly called E. coli) Yersinia, and Listeria.
- Medications that one takes long-term may cause chronic diarrhea, including antibiotic-associated diarrhea. Use of antibiotics can lead to an overgrowth of Clostridium difficile (C diff) bacteria in the intestines.
Parasites cause infection of the digestive system by the use of contaminated water. Common parasitic causes of diarrheal disease include Giardia lamblia, Entamoeba histolytica, and Cryptosporidium.
Intestinal disorders or diseases (including those that affect the small intestine or colon) including inflammatory bowel disease including ulcerative colitis and Crohn's disease, irritable bowel syndrome (IBS), diverticulitis, microscopic colitis, and celiac disease, and malabsorption (trouble digesting certain nutrients) are non-infectious causes of chronic diarrhea. Many of these disorders can cause the diarrhea to be yellow in color.
Reaction to certain medications can cause drug-induced diarrhea including antibiotics, blood pressure medications, cancer drugs, gout medications, weight loss drugs, and antacids (especially those containing magnesium).
Intolerance or allergies to foods such as artificial sweeteners found in sugar-free foods and lactose intolerance (to the sugar found in milk) can cause chronic diarrhea.
Alcohol abuse can cause diarrhea. Both binge drinking and chronic alcoholism may lead to loose stools.
Laxative abuse is one of the biggest self-induced causes of diarrhea, by taking too many laxatives, or taking them too frequently.
Diabetic diarrhea can be a complication of diabetes.
Radiation therapy or chemotherapy may cause loose stools and the diarrhea may last for up to three weeks after treatment ends.
Some cancers are more likely to cause diarrhea, including carcinoid syndrome, colon cancer, lymphoma, medullary carcinoma of the thyroid, pancreatic cancer, and pheochromocytoma.
Digestive surgery including stomach or intestinal surgery may cause diarrhea.
Running can cause diarrhea (sometimes referred to as "runner's trots"). This usually happens after longer distances over 10K or particularly hard runs.