It's possible that traveler's diarrhea may stem from the stress of traveling or a change in diet. But usually infectious agents — such as bacteria, viruses or parasites — are to blame. You typically develop traveler's diarrhea after ingesting food or water contaminated with organisms from feces.

Experiencing an increased frequency of bowel movements—or "traveler's diarrhea"—is a common physiological response to the change in environment, diet, and microbial exposure. When you travel to a new region, your digestive system is introduced to local strains of bacteria (like E. coli), viruses, and parasites that your immune system hasn't encountered before. Even if the food is prepared hygienically, your "gut microbiome" may struggle to process foreign spices, higher oil content, or different water mineralizations. Additionally, the stress of travel, disruptions to your circadian rhythm (jet lag), and increased consumption of alcohol or caffeine can stimulate the digestive tract. In 2026, health experts recommend a "boil it, cook it, peel it, or forget it" approach in high-risk areas. Staying hydrated with bottled water and taking a probiotic a week before your trip can help "prime" your stomach for the transition, but for most, the "frequency" is simply your body's way of rapidly flushing out unfamiliar substances as it acclimates to a new "normal."