Traveling can increase your chances of getting sick. It takes your body time to adjust to the water, food and air in another place. Water in developing countries can contain viruses, bacteria and parasites that cause stomach upset and diarrhea. Be safe by using only bottled or purified water for drinking, making ice cubes and brushing your teeth. If you use tap water, boil it or use iodine tablets. If you are traveling out of the country, you might also need vaccinations or prevention medicine. Which ones you need will depend on what part of the world you're visiting, the time of year, your age, overall health status and previous immunizations. See your doctor 4 to 6 weeks before your trip. Most vaccines take time to become effective. Bon voyage!