Diarrhea is loose, watery, and frequent stool. Diarrhea is considered chronic (long-term) when you have had loose or frequent stools for more than 4 weeks.

Diarrhea in adults is usually mild and goes away quickly without complications. In infants and children (especially under age 3), diarrhea can cause dehydration fairly quickly.

The most common cause of diarrhea is viral gastroenteritis, a mild viral infection that goes away on its own within a few days. This condition is often called the stomach flu. Viral gastroenteritis often occurs in mini-epidemics in schools, neighborhoods, or families.

Food poisoning and traveler's diarrhea are two other common causes of diarrhea. They occur as a result of eating food or drinking water contaminated with bacteria or parasites.

Medications, especially antibiotics, laxatives containing magnesium, and chemotherapy for cancer treatment, can also cause diarrhea.

• Malabsorption syndromes such as lactose intolerance
• Inflammatory bowel diseases (Crohn's disease and ulcerative colitis)
• Irritable bowel syndrome (IBS)
• Celiac disease

Other less common causes of diarrhea include:

• Zollinger-Ellison syndrome
• Nerve disorders like autonomic neuropathy or diabetic neuropathy
• Carcinoid syndrome
• Gastrectomy (partial removal of the stomach)
• High dose radiation therapy

• Drink plenty of fluid to avoid becoming dehydrated. Start with sips of any fluid other than caffeinated beverages. Milk may prolong loose stools, but also provides needed fluids and nourishment. Drinking milk may be fine for mild diarrhea. For moderate and severe diarrhea, electrolyte solutions available in drugstores are usually best.
• Active cultures of beneficial bacteria (probiotics) make diarrhea less severe and shorten its duration. Probiotics can be found in yogurt with active or live cultures and in supplements.
• Foods like rice, dry toast, and bananas can sometimes help with diarrhea.
• Avoid over-the-counter anti-diarrhea medications unless specifically instructed to use one by your doctor. Certain infections can be made worse by these drugs. When you have diarrhea, your body is trying to get rid of whatever food, virus, or other bug is causing it. The medicine interferes with this process.
• Rest.

If you have a chronic form of diarrhea, like the one caused by irritable bowel syndrome, try adding bulk to your diet -- to thicken the stool and regulate bowel movements. Such foods include rice, bananas, and fiber from whole-wheat grains and bran. Psyllium-containing products such as Metamucil or similar products can also add bulk to stools.