How to cut your risk of traveler’s diarrhea by more than half

Q: Last time I was on vacation, I got sick with diarrhea on Day 2 and was out for the remainder of the trip while everyone else had fun. We’re traveling abroad again, and I don’t want that to happen. Is it just bad luck?

A: Have a peek right now in your medicine cabinet, I bet you already have what you need: Pepto-Bismol, or more precisely, its active ingredient bismuth subsalicylate. This over-the-counter medicine, which you can buy almost anywhere, has been shown in multiple randomized controlled trials to reduce your risk of traveler’s diarrhea by 65%. Most people who come to my gastroenterology clinic have never heard this. Almost nobody packs it.

Around 1 in 3 people traveling abroad will get diarrhea, most commonly within the first week of the trip. That’s an enormous number of vacationers who end up instead as … party poopers.

Sorry. Had to.

Traveler’s diarrhea is caused by bacteria or viruses (and less frequently, parasites) transmitted through food and water. You can do everything right: careful restaurant choices, meticulous hand hygiene, a firm policy on ice. And sometimes you still end up ill, because what you ate was contaminated without anyone’s knowledge — so, unfortunately, luck does play a role here, too.

The good news is that most cases of traveler’s diarrhea are mild. The bad news is that “mild” is a relative term when your family has a snorkeling excursion at 9 a.m.

So if this is a once-in-a-lifetime trip, a 65% reduction in risk can be a real savior.

Bismuth subsalicylate has been around for over a century. The “pink stuff” has a genuinely solid track record of benefit in multiple randomized controlled trials: classic studies testing two tablets four times daily in U.S. students traveling to Mexico showed it confers 65% protection against traveler’s diarrhea. The bismuth component provides antibacterial and antiviral effects and, unlike antibiotics, it does not contribute to antimicrobial resistance or disrupt your gut microbiome.

Watch out for side effects like constipation and black stools or a darkened tongue, which are both harmless, but perhaps alarming if you aren’t expecting them.

There is a catch here: for it to work, the drug must be present at the exact time the pathogen arrives in your small bowel. Because the small bowel moves fast, that means you need to take four doses a day (two tablets per dose every 3-4 hours while awake, and no more than eight tablets in a 24-hour period).

Set an alarm. I recognize nobody wants to check their smartphone timer during a trek through Masai Mara, but a recent randomized trial of bismuth subsalicylate found that when travelers didn’t consistently take it as often as they should, it was not effective.

Do not take bismuth subsalicylate if you have kidney disease, gout or if you’re already taking daily aspirin (the salicylate load becomes a concern). Always check with your physician, but as a general rule, limit use to no more than three weeks at a stretch.

It also matters where you’re going. Latin America, sub-Saharan Africa and South and Southeast Asia would be considered high-risk destinations, whereas Western Europe, Japan, Australia and Canada would be low risk. So if you’re headed to Cancún or Bali for spring break, this is your fair warning (which is more than what traveler’s diarrhea gives you).

When I’m traveling abroad, I try to follow a few simple guardrails whenever possible:

• Eat at busy restaurants and at times when the locals eat. When I’m in India, for example, I eat dinner much later than I do at home in Boston. Timing your meals to match local rhythms minimizes the chances you’re eating food that has been languishing in a warming tray since the lunch rush. A full, humming restaurant also signals rapid turnover, which is exactly what you want from a kitchen.

• Order food that’s visibly steaming, and ask for it that way. The temperature required to kill bacterial enteropathogens is 59 degrees Celsius (or about 139 degrees Fahrenheit). If the food is actively steaming, that’s a good sign. If your dish arrives merely warm, it is not rude to politely send it back — it’s a safety issue.

• Avoid the buffet. In buffets, food sits at uncertain temperatures for uncertain lengths of time, touched by uncertain numbers of hands. The shrimp looked fine at 11 a.m. It is now 3 p.m. Walk past.

• Drink water that came from a bottle whose seal you broke yourself — and skip the ice. A fun cocktail filled with ice made from local tap water is doing the same thing to you that a cup of said tap water would do. Don’t forget that when your piña colada arrives.

• Choose fruits you peel yourself; approach salads with suspicion. A mango you’ve peeled yourself is a safer bet than cold leafy greens washed in local water. If you didn’t peel it, treat it as a calculated risk.

• Skip the tabletop sauces. Older studies have found that sauces kept at room temperature on restaurant tabletops, such as salsa, contain high levels of the bacteria that cause traveler’s diarrhea. I tend to give room temperature sauces a pass when I’m eating food from street vendors as well.

My patients often ask about taking probiotics on vacation, and as exciting as they sound, the data has not yet proved strong enough to recommend them to prevent traveler’s diarrhea.

On a similar vein, I do not recommend taking antibiotics “just in case” while you travel. Antibiotics carry real risks — they disrupt your microbiome, promote antimicrobial resistance and can invite complications that may be worse than the illness you were trying to prevent. If you do become sick, most cases of traveler’s diarrhea will resolve on their own without antibiotics.

What is usually more important is staying hydrated — try to take frequent small sips of water or electrolyte solutions — and rest. However, if you are unable to tolerate drinking or eating, or if you see any blood in your stool, develop a fever or severe abdominal pain, seek care locally promptly.