Having an Upset Stomach When Traveling: Why Does This Happen?

Many travel lovers get an upset stomach during the first few days in a new country. For some, diarrhea can last for a week or even more. Why does this happen, and can it be prevented?

Dr. Helga

General practitioner

A matter of habit

The main cause of travelers' upset stomach and diarrhea is an unfamiliar microflora that enters the body with food and drinks. Our intestines adapt to the food we consume regularly, and in a new country, the digestive tract encounters unfamiliar bacteria in new food components that it has not learned to digest. In the first days, the body reacts to unfamiliar food and water as "enemies," and acts in the only familiar way: flushing them out.

The second aspect that provokes diarrhea is hygiene (or lack thereof). In many countries, it is not recommended to drink tap water. Even brushing teeth or washing hands with tap water is discouraged, as the composition of new tap water is too much of a shock for the stomach. Bottled water is highly recommended whenever possible.

What should I look out for?

There are 5 primary things to keep in mind to prevent an upset stomach while traveling:

Water: buy it in supermarkets and never drink it from the tap. Use bottled water even for brushing teeth and washing hands, if possible.

Milk and dairy products: different sterilization and pasteurization techniques can make milk and dairy products an unacceptable product for your gut.

Fruits and vegetables: they are not dangerous by themselves, but due to their high fiber content they can alter the digestive process and have a laxative effect.

Raw foods: this is popular in Asia, but restaurants in other regions also serve raw food. Raw (or undercooked) food can seriously disrupt your usual digestive process.

Street food: this is a great way for many tourists to learn about local traditions, but there is no way to guarantee that the vendor washed his or her hands, the food was prepared cleanly, and the food itself hasn't expired. Therefore, there is a big risk in eating this.

Alcohol can cause dehydration, which can further disrupt the digestive process and cause an upset stomach. Therefore, try to limit alcohol intake until the stomach issues have passed.


The natural inclination, once the upset stomach or diarrhea has started, is to take something to stop it. However, this is exactly what you shouldn't do. During the first 24 hours, you should not interfere with the body to eliminate what it deems harmful. Drink more water, rest and let the gastrointestinal tract "flush" itself. A good sign will be light transparent urine: this means that you are getting enough liquid. If the urine becomes dark, orange, or cloudy, drink more water. If it remains the same, seek medical attention. Additionally, seek medical attention if diarrhea doesn’t go away after a day or so. Leave any treatment to medical professionals, and don’t try to self-medicate.

20 December 2021

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