Bacteria that may contaminate food or water include campylobacter, salmonella, shigella, and E. coli, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Viruses that can cause diarrhea include rotavirus (especially in children), Norwalk virus (found in some shellfish), cytomegalovirus, and viral hepatitis. People who are lactose intolerant are not able to digest the sugar found in milk and frequently have diarrhea if they drink milk or other dairy products. Diarrhea also may be caused by parasites such as giardia lamblia, entamoeba histolytica, and cryptosporidium. Diarrhea also may be caused by medicines such as antibiotics and antacids that contain magnesium.

Celiac disease is a digestive disease caused by the body's abnormal response to gluten, a protein found in wheat, rye, and barley. In people with celiac disease, the gluten causes a loss of the villi, the finger-like projections in the intestine that absorb nutrients and fluids. This leads to chronic diarrhea, gas, and other gastrointestinal problems. Irritable bowel syndrome is a disorder that interferes with the function of the large intestine (colon). Diarrhea is one symptom of IBS. Others include abdominal pain, bloating, and constipation. Diabetes can also cause constipation or diarrhea.

Before the rotavirus vaccine was first available in 2006, almost all children in the U.S. were infected with it before their fifth birthday. Rotavirus infection causes severe diarrhea and leads to hospitalization for thousands of children younger than 5 each year in the U.S., according to the CDC. Many of the cases occur in the winter and early spring. They are common in daycare centers and children's hospitals. Rotavirus diarrhea usually goes away in 3 to 8 days. Not all children infected with rotavirus have symptoms.

Acute diarrhea typically lasts only a few days to 4 weeks and usually is caused by a bacterial, viral, or parasitic infection. Chronic diarrhea is defined as diarrhea that lasts more than a month. It usually is a symptom of another condition such as celiac disease. According to the NIDDK, call your doctor if:

• Your diarrhea continues for more than 2 days
• You pass 6 or more loose stools in 24 hours
• You have severe pain in your belly (abdomen) or rectum
• You have a fever of at least 102° F (39° C)
• You have blood in your stool or have black, tarry stools
• You have signs of dehydration

Also call the doctor right away if: your child does not get better within 24 hours of developing diarrhea, the child has severe pain in the belly or rectum, if the child's stools contain blood or pus, or if they are black. Diarrhea can be dangerous in babies and young children because of the danger of dehydration. Don't give your child antidiarrhea medicine without checking with your doctor first. Medicines for adults may be dangerous when given to children.

Water is very important in preventing dehydration. But because you also need electrolytes, you can drink broth and soups. Soft fruits and vegetables are also good choices. Avoid beverages that contain caffeine such as coffee, tea, and soda. Fruit juice, sugary drinks, and sports drinks can make diarrhea and dehydration worse. For babies and children with more than mild diarrhea, a doctor usually recommends special beverages called oral rehydration solution. These contain electrolytes. You can buy oral rehydration solution at drugstores and most grocery stores.

It's best to eat soft, bland foods until your diarrhea goes away and avoid milk and milk products and foods that are greasy, high in fiber, or very sweet, according to the NIDDK. Children with diarrhea usually can continue to eat their normal diet, including milk, if the diarrhea is mild.

Other tips from the NIDDK include: Don't eat raw or rare meat or fish; don't eat meat or shellfish that is not hot when served; don't eat food from street vendors. Beverages that are safe to consume include bottled water that has been sealed, hot beverages such as coffee and tea, and carbonated soft drinks. You don't need to worry about traveler's diarrhea when visiting Canada, most European countries, Japan, Australia, or New Zealand.