You may blame it on a 24-hour bug or something you ate, but if you're like the average American, you'll suffer once or twice this year from diarrhea frequent, watery bowel movements that may be accompanied by painful cramps or nausea and vomiting.
Gastroenteritisthe catch-all medical term for intestinal flu, viral infection, and food poisoning is the second leading cause of missed work time (the common cold beats it).
Diarrhea is uncomfortable and unpleasant, but generally no big deal in otherwise healthy adults. However, if diarrhea becomes a chronic condition, the situation changes. If it affects the very young, the elderly, or the chronically ill, it can be dangerous. And if you're not careful to drink enough fluids, you could find yourself complicat-ing what should have been a simple situation.
What causes diarrhea? Because the condition generally lasts only a few days, doctors don't usually culture the stool to diagnose what started it in the first place. It's most often due to a viral infection, which antibiotics can't fight. You just have to tough it out for a couple of days. The virus has invaded the bowel, causing it to absorb excessive fluid, which leads to the watery stools. You may also experience cramping, nausea and vomiting, headache, fever, malaise, and even upper-respiratory-tract symptoms, such as a runny nose. One clue: If members of your family all get sick, but at different times, it's likely a virus that got passed around. Bacteria, which often cause traveler's diarrhea in certain parts of the world, can also be responsible for diarrhea as the result of food poisoning. When the whole family goes on a picnic and six hours later, they're all sick, that's a classic sign of food poisoning, says Rosemarie L. Fisher, M.D., professor of medicine in the Division of Digestive Diseases at Yale University School of Medicine in New Haven, Connecticut.
Much rarer are microbes like amoebae and giardia that try to set up permanent housekeeping
in your bowel, causing diarrhea that lasts for week or months. You can get these from contaminated food or water, public swimming pools, and communal hot tubs.
Certain drugs, especially antibiotics, can have diarrhea as a side effect. Magnesium-containing antacids and artificial sweeteners such as sorbitol are often overlooked culprits.
Unless diarrhea persists, you usually don't find out its cause. Treatment is aimed at relieving the symptoms and at preventing dehydration, the most serious consequence of diarrhea.
So what can you do?

Ride it out.
If you're not very young or old or suffering from any chronic illness, it may be safe just to put up with it for a couple of days. Although there's no definite proof that diarrhea is a cleansing action, it probably serves some purpose, explains Richard Bennett, M.D., assistant professor of medicine at Johns Hopkins University School of Medicine in Baltimore.
Keep hydrated.
In the meantime, make sure you maintain your fluid and electrolyte balance, as the doctors say. Obviously, you can lose a lot of liquid in diarrhea, but you also lose electrolytes, which are minerals like sodium and potassium, that are critical in the running of your body. Here's how to replace what you're losing:
Drink plenty of fluids. No one agrees on which fluid is best again, because of the electrolyte problem. The experts do agree you need at least two quarts of fluid a day, three if you're running a fever. Plain water lacks electrolytes, although you may want to drink this part of the time. Weak tea with a little sugar is a popular choice. Some vote for Gatorade, although Fisher points out it's constituted to replace fluids lost through sweating,not for diarrhea, a whole different ball game. Defizzed, nondiet soda pop is recommended by some, although anything with a lot of sugar can increase diarrhea. So can caffeine. Fruit juices, particularly apple and prune, have a laxative effect, but others may be OK.
Buy an over-the-counter electrolyte replacement formula. Pedialyte, Rehydralyte, and Ricelyte are available counter from your local drug store. These formulas contain fluids and minerals in the proper proportion.

Keep your liquids cool but not ice-cold.
Whatever you choose to drink, keep it cool, suggests Peter A. Banks, M.D., director of Clinical Gastroenterology Service at Brigham and Women's Hospital and lecturer on medicine at Harvard Medical School, both in Boston. It will be less irritating that way. Sip, don't guzzle; it will be easier on your insides.
Sip some chicken broth.
Or any broth, says Banks. But have it lukewarm, not hot, and add some salt.

Rest in bed.
Give your body a chance to fight the bug that's causing this.

Put a heating pad on your belly.
Banks says it will help relieve abdominal cramps.

Try yogurt.
You'll want to make sure you get a product that contains live lactobacillus cultures, which are friendly bugs that normally live in the gut. There are anecdotal reports but no good studies that yogurt works, says Bennett. But there's no harm in trying.
Eat light.
Soups and gelatin may go down easy. Banks recommends bland foods like rice, noodles, and bananas. Potatoes, toast, cooked carrots, soda crackers, and skinless, defatted chicken are also easy on the digestive system.

Take the pink stuff.
Stopping the diarrhea with an over-the-counter medication may not be the best thing for your body. Diarrhea probably reflects your body's attempt to get rid of a troublesome bug. If you do feel it's necessary, however, Pepto-Bismol is probably the safest over-the-counter antidiarrheal medicine, says Bennett. And studies show it may have a mild antibacterial effect, which would be most useful in traveler's diarrhea, since this condition is usually bacteria related

Take Kaopectate or Imodium A-D.
Again, you're probably better off going without antidiarrheal medication. If you absolutely need some relief, however, you can try one of these over-the-counter medications. Imodium A-D slows down the motility, or movement, of the gut; Kaopectate absorbs fluid. Bennett does not recommend these for elderly patients because decreased motility can be dangerous in an infection and can lead to worse problems.

Don't do dairy.
Avoid milk or other dairy products like cheese during the time that you're having diarrhea as well as for one to three weeks afterward. The small intestine, where milk is digested, is affected by diarrhea and simply won't work as well for a while. Milk may sound soothing, says Fisher. But it could actually make the diarrhea worse.

Cut out caffeine.
Just as it stimulates your nervous system, caffeine jump-starts your intestines. And that's the last thing you need to do in diarrhea.

Say no to sweet treats.
High concentrations of sugar can increase diarrhea. The sugar in fruit can do the same.

Steer clear of greasy or high-fiber foods.
These are harder for your gut to handle right now. It needs foods that are kinder and gentler.

The Young and the Old
For most people, diarrhea is nothing more than a minor inconvenience. But for the very young and the elderly, it can be life threatening, even fatal.
Why is it so dangerous for these groups? Young children have a much smaller blood volume, explains Harry S. Dweck, MD., director of the Regional Neonatal Intensive Care Unit at Westchester Medical Center in Valhalla, New York. What constitutes a small fluid loss in an adult can make a big difference in an infant.
Dehydration can take days to occur in an adult, hours to days for a child, and seconds to minutes in a newborn, Dweck emphasizes. That's why diarrhea has been such a killer of children in many countries around the world.
If your child has diarrhea, call the doctor right away, with the first loose stool, Dweck stresses.
Diarrhea may be harder to recognize in infants. Newborns may have up to 6 to 9 bowel movements a day, Dweck says. And if they're breast-fed, it's a more liquid stool. But parents generally learn fast what their baby's normal stool looks like. If it becomes more liquid, if it's explosive, or if the odor changes, it's probably diarrhea. The best way by far to prevent diarrhea in infants is to breast-feed, Dweck points out. The colostrum, the special kind of milk produced during the first few days of the baby's life, is loaded with antibodies and white blood cells that are absorbed directly into the baby's gastrointestinal tract, which will help prevent gastrointestinal infections down the road
There's also less chance of contamination with breast-feeding, since bottles don't have to be washed. And formula itself can cause allergic reactions that include diarrhea.
Diarrhea is less serious in children over 18 months of age, but diarrhea still warrants a call to the doctor Your physician will tell you how to treat your baby and what to give him or her to prevent dehydration and eletrolyte imbalance. Once kids reach the age of eight or so, you can follow the same recommendations for treating diarrhea as you would for adults.
The elderly can't stand to lose much fluid, either but that's because their circulatory system has changed with aging Hardening of the arteries occurs throughout the blood vessels in the body; lowered blood pressure that occurs when fluid is lost means there's not enough pressure to force blood to circulate.
That puts them at a high risk for stroke, heart attack, or kidney failure, explains Richard Bennett, M.D.
But when the elderly have diarrhea, it's often difficult to know when they're becoming dehydrated They don't recognize thirst as well, says Bennett. Or maybe they can't get around well enough to get a drink when they are thirsty. Changes in the skin that signal dehydration also aren't apparent in aged skin. The best clue: Are they still passing urine every hour or two?
If you're older and in good health but have a history of congestive heart failure and/or are taking diuretics, you should call your physician as soon as the diarrhea starts. The doctor may want to change your dosage of diuretics, since these drugs cause you to lose fluid, says Bennett.
Ironically, medical care can lead to some cases of diarrhea in the elderly, says Bennett. They're more likely to be on antibiotics, which can have diarrhea as a side effect. They're also prone to constipation and may self-medicate or have a physician recommend several types of laxatives, which can end up responsible for diarrhea. About half of the cases of diarrhea in the elderly are probably due to infections, the majority of which are viral.