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Montezuma's revenge, tourista and Tut's tummy are among the many nicknames given to this common ailment of travelers. Nothing can ruin a foreign vacation or business trip more quickly than loose stools and abdominal cramps. But this disorder usually isn't serious — it's just unpleasant.

A trip to a foreign country by no means guarantees gastrointestinal discomfort. But if you visit a place where the climate, social conditions or sanitary standards and practices are different from yours at home, you have an increased risk of developing diarrhea.

Each year millions of international travelers battle this illness. High-risk destinations for traveler's diarrhea include developing countries in Latin America, Africa, the Middle East and Asia. Traveling to southern Europe and a few Caribbean islands also poses some risk. However, your risk of traveler's diarrhea is generally low in northern Europe, Canada, Australia, New Zealand and the United States.

Being careful about what you eat and drink can reduce your risk.

Traveler's diarrhea usually begins abruptly while traveling or shortly after you return home. Most cases abate within three to four days without treatment and clear up within a week. However, you can have multiple episodes of traveler's diarrhea during one trip.

The most common signs and symptoms of traveler's diarrhea are:

• Increased frequency, volume and weight of stool
• Frequent loose stools — usually about four to five loose or watery bowel movements each day
• Abdominal cramps
• Nausea
• Vomiting
• Fever
• Bloating

A small number of cases involve moderate to severe dehydration, bloody stools, persistent vomiting or a high fever. If you or your child experiences any of these signs and symptoms or if the diarrhea lasts longer than a few days, it's time to see a doctor.

It's possible that traveler's diarrhea may stem from the stress of traveling, jet lag, fatigue, or change in diet or altitude. But almost always an infectious agent is to blame.

You typically develop traveler's diarrhea after ingesting food or water that's contaminated with organisms from feces. These organisms are infectious agents — including various bacteria, viruses and parasites — that enter your gastrointestinal tract and overpower your defense mechanisms, resulting in signs and symptoms of traveler's diarrhea.

The most common cause of traveler's diarrhea is enterotoxigenic Escherichia coli (E. coli) — or ETEC — bacteria. These bacteria attach themselves to the lining of your intestine and release a toxin that causes diarrhea and abdominal cramps.

So why aren't natives of high-risk countries affected in the same way? Often their bodies have become used to the bacteria and developed immunity to them.

Your chances of contracting traveler's diarrhea are mostly determined by your destination. But certain groups of people have a greater risk of developing the condition. These include:

• Children and young adults. Children younger than age 2 have a higher risk of contracting traveler's diarrhea, probably because of lack of immunity, as well as the tendency for them to put things in their mouths. The condition is also slightly more common in young adults ages 21 to 29. Though the reasons why aren't clear, it's possible that young adults lack acquired immunity, are more adventurous in their travels or are less vigilant in avoiding contaminated foods.
• People with a weakened immune system. A weakened immune system increases vulnerability to infections.
• People with diabetes or inflammatory bowel disease. Conditions such as these can leave you more prone to infection.
• People who take acid blockers or antacids. Acid in the stomach tends to destroy organisms, so a reduction in stomach acid may leave more opportunity for bacteria.
• People who travel during certain seasons. The risk of traveler's diarrhea is higher during the summer months and rainy seasons.

Traveler's diarrhea usually goes away on its own in about three or four days. Signs and symptoms may last longer and be more severe if the condition is caused by organisms other than common bacteria. In such cases, you may need prescription medications to help you overcome this ailment.

If you have severe dehydration, persistent vomiting, bloody stools or a high fever, or if your symptoms last for more than a few days, seek medical help. The local U.S. embassy or consulate can help you find a competent, English-speaking medical professional.

Be especially cautious with children, because traveler's diarrhea can cause severe dehydration in a short time. Call a doctor if your child is sick and exhibits any of the following signs or symptoms:

• Persistent vomiting
• Bloody stools or severe diarrhea
• A high fever
• Dry mouth or crying without tears
• Signs of being unusually sleepy, drowsy or unresponsive
• Decreased volume of urine, including fewer wet diapers in infants

Because you lose vital fluids, salts and minerals during a bout with traveler's diarrhea, you may become dehydrated. Children are especially vulnerable to dehydration, and it can be severe.

An oral rehydration solution (ORS) is the best way to replace lost fluids. These solutions contain water and salts in specific proportions to replenish both fluids and electrolytes. They also contain glucose or another carbohydrate such as rice powder to enhance absorption in the intestinal tract.

Bottled oral rehydration products are available in drugstores in developed areas, and many pharmacies carry their own brands. You can find packets of powdered oral rehydration solution, WHO-ORS, at stores, pharmacies and health agencies in most countries. Reconstitute the powder in bottled or boiled water according to the directions on the package.

If these products are unavailable, you can prepare your own rehydrating solution in an emergency by mixing together:

• 1/2 teaspoon salt
• 1/2 teaspoon baking soda
• 3 tablespoons sugar
• 1 liter safe drinking water

Be sure to measure accurately because incorrect amounts can make the solution less effective or even harmful.

You or your child can drink the solution in small amounts throughout the day as a supplement to solid foods or formula, as long as dehydration persists. Breast-fed infants also can drink the solution, but should continue nursing on demand. If dehydration symptoms don't improve, seek medical care right away. Oral rehydration solutions are intended only for urgent short-term use.

Because traveler's diarrhea tends to resolve itself, you may get better with self-care. If these techniques aren't working, you can turn to several medications to help relieve symptoms.

• Antimotility agents. These agents — which include loperamide (Imodium), medications containing diphenoxylate (Lomotil), and opiates, such as paregoric and codeine — provide prompt but temporary relief by reducing muscle spasms in your gastrointestinal tract, slowing the transit time through your digestive system and allowing more time for absorption. They aren't recommended for infants or people with fever or bloody diarrhea, as they can delay clearance of the infectious organisms and make the illness worse. Also, don't use them if signs and symptoms last more than 48 hours. In such cases, see a doctor.
• Bismuth subsalicylate (Pepto-Bismol). This over-the-counter medication can decrease the frequency of your stools and shorten the duration of your illness. However, it isn't recommended for children, pregnant women or people who are allergic to aspirin.
• Antibiotics. If you have severe symptoms or three or more loose stools within eight hours, a doctor may prescribe a three- to five-day course of antibiotics.

Before you leave for your trip, talk to your doctor about appropriate medications to take with you so that you don't have to buy diarrhea medications while overseas. Some of the drugs available abroad are unsafe and have been banned in the United States.

Watch what you eat
The general rule of thumb is this: Boil it, cook it, peel it or forget it. Unfortunately, most travelers don't stick to these guidelines 100 percent of the time. Remember these tips:

• Don't buy food from street vendors.
• Avoid unpasteurized milk and dairy products, including ice cream.
• Avoid raw or undercooked meat, fish and shellfish.
• Steer clear of moist food at room temperature, such as sauces and buffet offerings.
• Eat foods that are well cooked and served hot.
• Munch on dry foods — like breads — and high-sugar-content foods, such as jellies and syrups.
• Stick to fruits and vegetables that you can peel yourself, such as bananas, oranges and avocados. Stay away from salads and unpeelable fruits, such as grapes and berries.

Don't drink the water
When visiting high-risk countries, keep the following tips in mind:

• Avoid unsterilized water — from tap, well or stream. If you need to consume local water, boil it for five to ten minutes.
• Avoid ice cubes or fruit juices made with tap water.
• Beware of sliced fruit that may have been washed in contaminated water.
• Don't swim in water that may be contaminated.
• Keep your mouth closed while showering.
• Feel free to drink canned or bottled drinks in their original containers — including water, carbonated beverages, beer or wine — as long as you break the seals on the containers yourself. Wipe off any can or bottle before drinking or pouring.
• Use bottled water to brush your teeth.
• Use bottled or boiled water to mix baby formula.
• Order hot beverages, such as coffee or tea, and make sure they're steaming hot.

If it's not possible to buy bottled water or boil your water, bring some means to purify water: Consider a water-filter pump with a microstrainer filter that can filter out small microorganisms. Look in camping stores for a filter that is certified by the National Science Foundation. Or chemically disinfect water with iodine or chlorine. Iodine tends to be more effective, but is best reserved for short trips, as too much iodine can be harmful to your system. You can purchase iodine tablets or crystals at camping stores and pharmacies. Be sure to carefully follow the directions.

Follow additional tips
Here are other ways to reduce your risk of traveler's diarrhea:

• Make sure dishes and utensils are clean and dry before using them.
• Wash your hands often and always before eating.
• Seek out food items that require little handling in preparation.
• Keep children from putting things — including their dirty hands — in their mouths. If possible, keep infants from crawling on dirty floors.
• Tie a colored ribbon around the bathroom faucet to remind you not to drink — or brush your teeth with — tap water.

Other preventive measures
Public health experts generally don't recommend taking antibiotics to prevent traveler's diarrhea, because doing so can contribute to the development of antibiotic-resistant bacteria. Besides, antibiotics provide no protection against viruses and parasites, but they can give travelers a false sense of security about the risks of consuming local foods and beverages. They can also cause unpleasant side effects, such as skin rashes, skin reactions to the sun, vaginal yeast infections and, rarely, blood disorders.

As a preventive measure, some doctors suggest taking bismuth subsalicylate (Pepto-Bismol), which has been shown to decrease the likelihood of diarrhea. However, don't take this medication for longer than three weeks, and don't take it at all if you're allergic to aspirin, pregnant or taking certain medications, such as anticoagulants. Common harmless side effects include a black-colored tongue and dark stools. In some cases it can cause constipation, nausea and, rarely, ringing in your ears (tinnitus).

Researchers are working on a vaccine that could prevent most cases of traveler's diarrhea by protecting against the most common infectious causes. But a traveler's diarrhea vaccination is still a long way off.

If you do get traveler's diarrhea, avoid alcohol, caffeine and dairy products, which may worsen symptoms or increase fluid loss. But keep drinking fluids.

Drink canned fruit juices, weak tea, clear soup, decaffeinated soda or sports drinks to replace lost fluids and minerals. Later, as your diarrhea improves, try a diet of easy-to-eat complex carbohydrates, such as salted crackers, bland cereals, bananas, applesauce, dry toast or bread, rice, potatoes, and plain noodles. Once diarrhea goes away, you may return to your normal diet. Just be sure to add dairy products, caffeinated beverages and high-fiber foods cautiously.