4 Common Diarrhea Causes--and What to Do if You Get Sick

May as well add diarrhea to that saying about death and taxes. It's not pleasant, but we all have to deal with it at one point or another.

Each year, American adults experience, on average, one bout of acute diarrhea--passing loose stools for one to two days. Young kids get it at twice that rate, according to the National Digestive Diseases Information Clearinghouse of the National Institutes of Health.

Most cases of diarrhea do resolve themselves on their own. However, you should be evaluated by a doctor for any case that lasts longer than a few days, or if you see blood in your stool. Other reasons to see a doctor quickly: severe pain in your stomach or rectum or a fever of 102 degrees or higher. (The American Academy of Family Physicians offers a flowchart to help evaluate your symptoms.) Meantime, it's important to avoid becoming dehydrated by drinking plenty of fluids. If you nevertheless develop signs of dehydration, like dry mouth or decreased urination, seek medical attention. Diarrhea can be caused by many factors, including inflammatory bowel disease, also known as IBD, irritable bowel syndrome, aka IBS, and viral or bacterial infections. A bad reaction to a medication can also be responsible.

Here are more details on some of the most common culprits:

* Inflammatory bowel disease includes Crohn's disease and ulcerative colitis, both of which cause inflammation in the lining of the digestive tract, which can result in diarrhea and other symptoms such as rectal bleeding, pain, fever, and weight loss. Today, people with Crohn's usually first get treated with medications to help decrease inflammation, including sulfasalazine (Azulfidine), mesalamine (Asacol or Pentasa), and olsalazine (Dipentum). Steroids, sometimes in combination with immunosuppressive medications, are often used to treat Crohn's disease. A medication called infliximab (Remicade) is typically recommended for moderate-to-severe Crohn's that fails to respond to other types of therapy. Some data suggest that giving patients infliximab (Remicade) and an immunosuppressant called azathioprine (Azasan) early in the course of illness can help keep Crohn's disease in remission.

Ulcerative colitis is treated similarly with olsalazine, mesalamine, or balsalazide (Colazal). Corticosteroids and immunosuppressive medications also are used to treat this condition. Some people will eventually need surgery for IBD, but newer, minimally invasive techniques can help patients avoid full removal of the colon and consequently the need to wear a colostomy bag to collect waste.

* Irritable bowel syndrome is sometimes confused with IBD, but the conditions are different. IBD "really is an inflammation of the bowel, as opposed to IBS, where there is no inflammation," says Geoffrey Nguyen, an associate professor of medicine at the University of Toronto and adjunct assistant professor at the Johns Hopkins School of Medicine. Symptoms range from stomach pain and bloating to constipation and diarrhea. According to the Mayo Clinic, the extent to which food allergies and intolerances may affect IBS is still unclear.

[See Making Sense of the Gluten-Free Food Frenzy]

Properly treating IBS requires recognizing the factors that trigger its symptoms, says Aaron Tokayer, a gastroenterologist at Montefiore Medical Center in New York and associate professor of clinical medicine at Yeshiva University's Albert Einstein College of Medicine. Greasy, fatty, or fried foods may bring on diarrhea in people with IBS, as may psychological stress; triggers can vary from person to person. The American College of Gastroenterology provides a quiz and "treatment matrix" on its website (gi.org) to help sufferers find relief.

* Bacterial infections caused by E. coli, campylobacter, and salmonella can be picked up through contaminated food or drink. Protect yourself against these bad bugs through proper food storage and refrigeration. And always ensure that "foods are cooked properly, so that bacterial germs don't survive," Tokayer advises.

[See Mistakes That Up Your Risk of Food Poisoning]

A 2009 study found another compelling reason to avoid these germs: People who'd had stomach infections caused by salmonella or campylobacter were found to be at increased risk for developing IBD later on. The study used data from laboratory registries to compare 13,149 people who had these infections with 26,218 people who hadn't been exposed to the germs. In the exposed group, 107 people were later diagnosed with IBD, compared with 74 people in the unexposed group.

The good news is that if you're healthy and pick up a germ that makes you ill, you will probably get better in a matter of days. Assuming that a doctor can determine which germ made you sick, antibiotics may be prescribed for people who have persistent diarrhea or a compromised immune system.

* A viral infection--or viral gastroenteritis--caused by such bugs as the rotavirus and norovirus triggers symptoms similar to those of a bacterial infection but can't be attacked by antibiotics. Treatment involves plenty of rest and hydration.

Don't be too quick to go back to your favorite greasy or spicy foods once you're on the mend. A bland diet--such as rice, toast, bananas and applesauce--is often recommended as you resume solid foods.

As with bacterial infections, you can prevent viral infections through proper handling of food and washing your hands often.

[See Back-to-School Germs to Avoid]

Updated on 09/07/2012: This article was originally published on June 5, 2009. It has been updated by Rachel Pomerance.