Many people have occasional diarrhea -- typically from a bug that gets into the gut. You enjoy a nice dinner out, let's say, but a few hours later find yourself communing with the commode.
Here's what's happening: "A bacteria or virus stimulates the intestine to contract more rapidly or more vigorously -- or stimulates the intestine to produce more fluid," says Bernard Aserkoff, MD, medical director of gastroenterology at Massachusetts General Hospital in Boston. "It usually last a few days."
Stress can also bring on a brief bout of diarrhea. "We're nervous, under some kind of stress, and almost the first thing we feel is cramps and rumbling in the stomach," Askeroff tells WebMD. "Some people have a sensitive or overactive bowel, which can also prompt the intestine to act up at times."
Inside Chronic Diarrhea
When diarrhea is a constant on-and-off problem -- chronic diarrhea -- it's a very different matter. Some people have it twice a week, says Aserkoff. "Lots of people have bad digestive systems."
Figuring out the cause of your gastrointestinal problems can take some investigative work, as many factors like food or some medications can trigger diarrhea.
"People who have this a lot -- either chronic or recurrent diarrhea -- need to see a doctor to make sure it's not a medical condition that needs specific treatment," Askerhoff says.
Irritable bowel syndrome (IBS) is a common problem. The episodes of diarrhea have been described as "violent" -- and often alternate with constipation. "It's a very complicated disorder," says Askeroff. "We don't really know why [people] have it, what's underlying it."
Studies suggest that the colon is hypersensitive, overreacting with spasms to even mild stimulation. One new theory suggests that the disorder involves brain chemicals (like serotonin) that affect nerve signals between the brain and the GI tract.
A few specific triggers of persistent diarrhea are well-known:
Food sensitivities -- lactose intolerance, celiac disease (intolerance to gluten protein in wheat, rye, and barley products), or sensitivity to spicy or fatty foods.