Most diarrhea is preventable. Whether you’re preparing for international travel, managing a sensitive stomach, or just tired of unexpected flare-ups, the strategies that work best target the two main causes: infectious organisms you ingest and foods that overwhelm your gut’s ability to absorb water. Proper handwashing alone cuts diarrhea episodes by roughly 30%, and the other measures below stack on top of that.
Handwashing Is the Single Best Defense
A large Cochrane review covering more than 50,000 children found that handwashing promotion reduced diarrhea episodes by about one-third in high-income countries and roughly 28% in lower-income settings. The key is timing: wash with soap and water before eating, after using the bathroom, and after touching shared surfaces like doorknobs or public transit handrails. Twenty seconds of scrubbing with regular soap is enough. Antibacterial soap offers no meaningful advantage over plain soap for preventing diarrhea.
When soap and water aren’t available, an alcohol-based hand sanitizer (at least 60% alcohol) works against most bacteria and viruses. It does not, however, kill certain parasites like Cryptosporidium, so handwashing with water remains the gold standard when you’re in areas where parasitic infections are common.
Know Your Dietary Triggers
Some diarrhea has nothing to do with infection. It happens when unabsorbed sugars pull excess water into your intestines, a process called osmotic diarrhea. The two most common culprits are lactose (in dairy) and sugar alcohols like sorbitol, xylitol, and mannitol found in sugar-free gum, mints, protein bars, and “diet” snacks.
Sorbitol causes gas, cramping, and urgency at doses as low as 5 to 20 grams per day. Above 20 grams, outright diarrhea is common. To put that in perspective, a single stick of sugar-free gum contains about 1 to 2 grams of sorbitol, but a sugar-free candy binge or a few “light” yogurts in a day can easily push you past the threshold. If you notice a pattern of loose stools after consuming these products, check ingredient labels for any word ending in “-ol” (sorbitol, maltitol, erythritol).
If dairy is your trigger, you likely have some degree of lactose malabsorption. Hard cheeses and yogurt are usually tolerated because fermentation breaks down much of the lactose, while milk, ice cream, and soft cheeses are more likely to cause problems. A lactase enzyme tablet taken before a meal can prevent symptoms entirely for most people.
Cook and Store Food Safely at Home
Foodborne bacteria like Salmonella, E. coli, and Campylobacter are destroyed at specific internal temperatures. Using a meat thermometer takes the guesswork out of it:
- Poultry (all cuts, including ground): 165°F (73.9°C)
- Ground beef, pork, or lamb: 160°F (71.1°C)
- Steaks, chops, and roasts (beef, pork, veal, lamb): 145°F (62.8°C), then rest for at least 3 minutes
Cross-contamination is the other major kitchen risk. Use separate cutting boards for raw meat and produce, and wash hands, utensils, and surfaces with hot soapy water after handling raw protein. Refrigerate leftovers within two hours. Bacteria multiply rapidly in the “danger zone” between 40°F and 140°F, so food left on a counter for a summer afternoon party is a common, preventable source of diarrhea.
Preventing Traveler’s Diarrhea
Traveler’s diarrhea affects up to 40% to 60% of people visiting high-risk regions in Latin America, Africa, the Middle East, and parts of Asia. It’s almost entirely a food and water problem, and the classic advice still holds: eat it hot, peel it yourself, or skip it.
Safe Eating Abroad
Stick to food that’s served steaming hot. Avoid raw salads, fresh salsas, uncooked sauces, and pre-cut fruit from vendors. Even if the produce itself is clean, contamination often happens during preparation. Fruits you can peel yourself (bananas, oranges, mangoes) are generally safe. Ceviche and other dishes “cooked” in citrus juice or vinegar do not reach temperatures that kill bacteria or parasites.
Street food isn’t automatically dangerous, but apply the same rules: choose items cooked to order and served hot. A freshly grilled skewer from a busy stall is typically safer than a lukewarm buffet at a hotel. Hot coffee and tea served steaming are also safe, since the brewing temperature kills pathogens.
Safe Drinking Abroad
Drink only bottled, boiled, or chemically treated water. Boiling is the most reliable method because it kills bacteria, viruses, and parasites at any altitude (a rolling boil for one minute is sufficient). UV purifiers also work well. Iodine tablets are effective against bacteria and many viruses, and they inactivate Giardia cysts under normal water conditions. However, under worst-case conditions (cold, murky water with high pH), iodine killed only about 35% of Giardia cysts in one study, so boiling or UV treatment is preferable when water quality is uncertain.
Don’t forget about ice. In high-risk areas, ice in drinks is made from local tap water and carries the same risk as drinking it directly. Brush your teeth with bottled water too.
Prophylactic Medications for Travel
Bismuth subsalicylate (the active ingredient in Pepto-Bismol) taken preventively reduced traveler’s diarrhea by 65% in a clinical trial when participants took two tablets four times daily (about 2.1 grams per day) for up to three weeks. A lower dose of one tablet four times daily still provided 40% protection. Common side effects include a harmless black discoloration of the tongue and stools, and it should be avoided by anyone taking blood thinners or with an aspirin allergy.
Preventive antibiotics are generally not recommended for routine travelers. The CDC reserves prophylactic antibiotics for short-term travelers with specific medical vulnerabilities, such as people who are immunocompromised. When antibiotics are considered, rifaximin is the current preferred option, since older choices like fluoroquinolones now face widespread bacterial resistance and carry risks including tendon damage and secondary infections.
Probiotics for Prevention
Certain probiotic strains can reduce the risk of specific types of diarrhea. Saccharomyces boulardii, a beneficial yeast, has the strongest evidence for preventing antibiotic-associated diarrhea and recurrent C. difficile infection. Lactobacillus GG and Lactobacillus reuteri also show benefit, particularly in children with viral gastroenteritis.
If you’re about to start a course of antibiotics and you’ve experienced antibiotic-related diarrhea before, starting a probiotic containing S. boulardii on the first day of your antibiotic course (and continuing for a few days after finishing) is a reasonable preventive step. For traveler’s diarrhea, the evidence for probiotics is less consistent, and the dietary and hygiene strategies above offer more reliable protection.
Water and Sanitation When Outdoors
Hikers, campers, and anyone drinking from streams or lakes face Giardia and Cryptosporidium, two parasites that cause prolonged watery diarrhea and are notoriously resistant to chemical disinfection. Boiling remains the most reliable purification method. Portable pump filters rated to remove particles down to 1 micron will physically remove both parasites. UV light devices (like SteriPEN) are effective in clear water but lose reliability in turbid water where particles can shield organisms from the light.
Never assume a stream is clean because it looks clear or flows quickly. Animal waste upstream is invisible, and a single mouthful of contaminated water can deliver enough Giardia cysts to cause infection.
Preventing Diarrhea Before a Stressful Event
Stress and anxiety activate the gut-brain connection, speeding up intestinal contractions and sometimes triggering urgent, loose stools. If you know that job interviews, exams, flights, or public speaking tend to set off your stomach, the pattern is worth addressing directly.
Eating a low-residue meal (white rice, toast, lean protein) the night before and morning of a stressful event reduces the volume of material moving through your colon. Avoid coffee, high-fiber foods, and large fatty meals in the hours before. Some people find that a low dose of loperamide (Imodium) taken the morning of a high-stakes event prevents symptoms entirely, though this is best reserved for occasional use rather than a daily habit. Longer-term, managing the underlying anxiety through breathing exercises, cognitive behavioral techniques, or therapy can reduce gut symptoms at their source.