Traveler’s diarrhea affects 30% to 70% of people during a two-week trip abroad, depending on destination and season. The good news is that most stomach trouble during international travel is preventable with preparation that starts weeks before your flight. Here’s how to get your gut ready and keep it healthy while you’re away.
Know Your Risk Level
Your destination matters more than almost anything else. Travel to South Asia, Southeast Asia, Central America, West Africa, and East Africa carries the highest risk of stomach illness. The Middle East, parts of the Caribbean, and South America fall into an intermediate range. Western Europe, Japan, Australia, and North America are low-risk destinations where food and water infrastructure is tightly regulated.
Certain personal factors also raise your vulnerability. If you take acid-reducing medications (the kind prescribed for heartburn or reflux), your stomach produces less of the acid that kills harmful bacteria in food and water. Recent antibiotic use is another risk factor, because it disrupts the balance of protective bacteria in your gut. If either applies to you, talk to your provider about whether to adjust your medications before departure.
Build Up Your Gut Bacteria Early
A diverse, healthy population of gut bacteria acts as your first line of defense against foreign pathogens. You can start strengthening that ecosystem two to four weeks before travel by increasing your fiber intake from a variety of sources: vegetables, legumes, whole grains, and fermented foods like yogurt, kimchi, or sauerkraut. Fiber feeds the beneficial microbes in your intestines, which in turn produce compounds that reinforce your intestinal lining and help regulate immune responses. A diet low in fiber and high in processed foods does the opposite, leaving your gut less resilient right when you need it most.
Probiotic supplements are another option. While research on specific strains is still evolving, many travel medicine specialists recommend starting a probiotic at least one to two weeks before departure so the bacteria have time to colonize your gut before you’re exposed to new pathogens.
Get Vaccinated With Enough Lead Time
Two vaccines protect against infections that hit the stomach directly, and both require planning ahead. The oral typhoid vaccine involves swallowing one capsule every other day for a total of four capsules, with the last dose taken at least one week before travel. Each capsule needs to be swallowed whole (not chewed) about an hour before eating, with cold or lukewarm water. Protection lasts about five years.
The oral cholera vaccine also needs to be completed before you leave, with timing that varies by product. If your destination has active cholera transmission, especially parts of sub-Saharan Africa or South Asia, schedule a travel medicine appointment at least four to six weeks before departure to leave room for the full course.
Pack the Right Stomach Supplies
A few items in your bag can make the difference between a minor inconvenience and days lost to illness. Bismuth subsalicylate (the active ingredient in Pepto-Bismol) has been studied as a preventive measure during travel. In a clinical trial, travelers who took a higher dose four times daily saw a 65% reduction in diarrhea, while a lower dose provided 40% protection. It’s available over the counter, though the frequent dosing and the fact that it turns your tongue and stool black make it impractical for some people.
Pack oral rehydration supplies as well. If diarrhea does strike, dehydration is the real danger. You can buy pre-made oral rehydration salt packets, or memorize this World Health Organization formula: 8 teaspoons of sugar, half a teaspoon of salt, mixed into 1 liter of clean water. This ratio matches what your intestines need to absorb fluid efficiently, and it works far better than water alone.
Your doctor may also prescribe a standby antibiotic for you to carry, particularly if you’re heading to a high-risk region or have a condition like inflammatory bowel disease that makes infection more dangerous. This isn’t for prevention. It’s a rescue medication you take at the first sign of severe symptoms, so you’re not scrambling to find a pharmacy in an unfamiliar city.
Water Safety Goes Beyond “Don’t Drink the Tap”
Contaminated water is a primary source of stomach illness abroad, but the risks extend well beyond what comes out of the faucet. Ice in drinks, water used to wash salads, and even brushing your teeth with tap water can expose you. In high-risk destinations, stick to sealed bottled water, or treat water yourself.
Your best portable option is a filter rated as an EPA-designated “purifier,” which removes at least 99.9999% of bacteria, 99.99% of viruses, and 99.9% of parasites like Giardia and Cryptosporidium. Standard microfilters (with pores under 1 micron) handle bacteria and parasites well but may miss viruses.
UV light devices kill bacteria, viruses, Giardia, and Cryptosporidium effectively, making them a lightweight backup. Chemical disinfection with iodine or chlorine tablets works against most bacteria and viruses, and will kill Giardia with extended contact time, but performs poorly against Cryptosporidium even with long waits. If you’re trekking in areas where Cryptosporidium is a concern, filtration or UV is the safer choice.
Hand Hygiene That Actually Works
This sounds basic, but how you clean your hands matters more than you might expect. Alcohol-based hand sanitizer is convenient, and it does reduce many bacterial pathogens. But against norovirus, one of the most common causes of stomach illness worldwide, soap and water is significantly more effective. In lab testing, washing hands with soap and water for 30 seconds completely removed norovirus from finger pads. Alcohol-based sanitizer showed inconsistent results, ranging from little to no reduction in some norovirus strains.
Carry sanitizer for moments when a sink isn’t available, but wash with soap and water before eating whenever you can. This single habit is one of the most powerful tools you have.
Eating Smart in the First Few Days
Your gut needs time to adjust to new microbial environments, and the first 48 to 72 hours of a trip are when you’re most vulnerable. Start with cooked foods served hot. Avoid raw vegetables, unpeeled fruit, street food with standing sauces, and buffets where food has been sitting at room temperature. As your system acclimates, you can gradually expand what you eat.
The classic traveler’s rule still holds: boil it, cook it, peel it, or forget it. Steaming-hot dishes from busy stalls with high turnover are generally safer than lukewarm plates at an empty restaurant, because high heat kills pathogens and fast turnover means food hasn’t been sitting out. Dairy products made from unpasteurized milk, including soft cheeses and fresh cream, are another common source of trouble in regions without strict food safety standards.
If you do develop mild diarrhea, ease back to bland, binding foods like rice, bananas, and toast. Use your oral rehydration solution to stay hydrated, and give your gut a day or two to recover before returning to adventurous eating. Most cases of traveler’s diarrhea resolve within three to five days without medical intervention.