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What Causes Diarrhea?

By Joanne Barker
WebMD Feature
Reviewed by Louise Chang, MD

Diarrhea is inconvenient, unpleasant, and happens to nearly everyone. Of all reported illnesses in the U.S., diarrhea is the second most common. The average adult has diarrhea four times a year. American children typically have seven to 15 cases of diarrhea by the time they reach age five.

Everyday things such as food, medication, or stress can cause diarrhea. However, diarrhea sometimes may signal an underlying medical condition. If diarrhea keeps you running for the toilet, read on to learn about some common triggers and how you can cope.

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If your bowel habits are sluggish and you suffer constipation, maybe some exercise can help speed things up. According to experts, exercise does more than tone your heart and other muscles. Exercise is essential for regular bowel movements. In fact, one of the key risk factors for constipation is inactivity.

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Bacterial Causes of Diarrhea

Bacteria are part of everyday life, and normally bacteria and humans live together peacefully. However, some bacteria can wreak havoc on your digestive well-being. These tiny bugs find fertile breeding ground in raw meats, eggs, shellfish, and unpasteurized milk.

Cases of food contamination causing diarrhea are rare in the U.S., says Alexander Rapisarda, MD, a specialist in gastroenterology and hepatology at Robert Wood Johnson University Hospital in East Brunswick, N.J. He tells WebMD, “The most common food-related cases of diarrhea come from food that was not refrigerated well enough or went bad before the patient ate it.”

To reduce your risk of bacteria-related diarrhea, cook meat, poultry, and eggs completely. Wash your hands, utensils, and surfaces. Refrigerate leftovers quickly, don’t leave them at room temperature longer than necessary.

When deciding where to dine out, look for health department ratings online or posted in the restaurant. These ratings indicate the restaurant kitchen’s levels of cleanliness and food safety.

Viral Causes of Diarrhea

Some viral infections can lead to diarrhea and vomiting. These viral strains are highly contagious, traveling easily from unwashed hand to unwashed hand. Shared drinks, utensils, and contaminated food also provide passage into your unsuspecting stomach. People who no longer have symptoms or never exhibited symptoms in the first place can sometimes spread these viruses.

Just like with bacteria, hand washing, clean kitchens, and common sense go a long way to keep viruses under wraps. If you or someone you know has diarrhea, do not eat or drink from the same containers. You might never know for sure if a bacteria or virus caused your diarrhea — the symptoms and incubation periods are often the same. In either case, the diarrhea and stomach upset usually work their way out of your system within two to three days.

Traveler’s Diarrhea

Delhi Belly and Montezuma’s Revenge are two nicknames for an experience shared by many unhappy travelers. Depending on the country, between 30% and 70% of travelers suffer a bout of diarrhea and vomiting, courtesy of contaminated local foods or water. If you travel to a developing country, avoid raw, unpeeled produce and water from the faucet. Eat only cooked foods prepared in a clean kitchen and stick with bottled water, even to brush your teeth. Typically, traveler’s diarrhea works its way out of your system within 12 hours.

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