Digestive Disorders Health Center

Traveler's Diarrhea

How Can I Make Water Safe to Drink?

Boiling is the most reliable method to make water safe to drink. Bring water to a vigorous boil, then allow it to cool; do not add ice. At high altitudes, allow water to boil vigorously for a few minutes or use chemical disinfectants. Chemical disinfection can be achieved with either iodine or chlorine. Iodine usually provides greater disinfection.

For disinfection with iodine, use either tincture of iodine or tetraglycine hydroperiodide tablets, such as Globaline or Potable-Aqua. These disinfectants can be found in sporting goods stores and pharmacies.

Read and follow the manufacturer's instructions. If the water is cloudy, strain it through a clean cloth and double the number of disinfectant tablets added. If the water is very cold, either warm it or allow increased time for the disinfectant to work. Adding a pinch of salt or pouring water from one container to another will improve the taste.

Portable water filters are not recommended due to lack of independently verified results of the filters' effectiveness.

As a last resort, if no source of safe drinking water is available, tap water that is uncomfortably hot to the touch may be safer than cold tap water. However, many disease-causing organisms can survive the usual temperature reached by the hot water in overseas hotels and boiling or proper disinfection is still advised.

What Precautions Should I Take With Food?

Food should be selected with care. Foods you should avoid include:

• Salads
• Uncooked vegetables and fruit. If you peel fruit yourself, it is generally safe.
• Unpasteurized milk and dairy products
• Raw meat and shellfish

Food that has been cooked and is still hot is usually safe. Some fish is not guaranteed to be safe, even when cooked, because of the presence of toxins in its flesh. Tropical reef fish, red snapper, amberjack, grouper, and sea bass can occasionally be toxic at unpredictable times if they are caught on tropical reefs rather than in the open ocean. The barracuda and puffer fish are often toxic and should generally not be eaten. Seafood from the islands of the West Indies and the tropical Pacific and Indian Oceans should be avoided, as it is more likely to contain toxins.