Tourists should be aware that there is a risk of contracting sicknesses from the local food and water. But if you eat smart and drink smart you should be fine. Always use bottled water and watch the salads that you eat, as they may be washed in tap water.  You are safer eating at the resort than in a restaurant should you decide to travel inland to any small village. Cooked food should always be safe, but must be well cooked.  Be careful not to get water in your mouth when you shower, and make sure to brush your teeth and rinse your toothbrush with bottled water. Also at some of the hotels, it may smell like sewage near gardens or soil. It is NOT sewage, but it is the smell that come from the heat that contacts with the soil.

There is also a risk of contracting malaria from mosquitoes, malaria is endemic to parts of the Dominican Republic. There is also a risk of dengue fever. Be sure an use an insect repellent with "deet".

Your doctor can prescribe a medication for you to take along with you that you can use only if you feel you have contracted something. 

for more information see the CDC site http://snipurl.com/20ii3 

or the Canadian site http://snipurl.com/20ihz 

Here is a quick tip posted recently by Kaki, Local Expert for La Romana

Drink lots of (bottled) water! Have a glass of water for every drink or at least every two alcoholic beverages.

Some people take Pepto Bismol in the morning or before every meal as a preventative measure. There are side effects to beware of (weird black tongue among them!) as with all medication so though you are using it for one battle, make sure that you know what you are ingesting. It can also act to stop you up so you won't get diahrrea but it could lead to the opposite problem. The nature of the product is that it provides protection by coating your stomach. You should beware of that if you are taking some other medication orally which you are expecting will be absorbed through the stomach walls. Effectiveness will be blocked.

If you get sick anyway and start taking Immodium, stop the Pepto Bismol therapy immediately. They don't mix. If you are staying around the hotel and can find the diahrrea merely an inconvenience, wait it out and flush your system as opposed to stopping nature from doing its job. See if you can only take the Immodium if you are heading out on an excursion or flying home. If you have something in your system that needs to be eliminated, beware that taking Immodium or something like that that is keeping it in your body could make you suffer with cramps and other abdominal pain or discomfort. It really is best in that situation to lay low, stay out of the sun, eat bananas and bread and white rice, drink lots of water, and let it pass in the natural way.

Some people bring a prescription for the antibiotic Cipro with them. As far as antibiotics go, it's a strong one and you should be sure that you follow the instructions provided for diagnosing the correct time to start taking it. Generally, it's when you see the presence of blood and once you've had the diahrrea for a full 24 hours. It's not recommended for those under the age of 16 years and it's not to be taken when you have a stomach ache or general diahrrea. Many Travelers follow a natural course of prevention by means of acidophilus and probiotic dairy products. Both act to increase the good bacteria in your system to counteract nasty bacteria. You can start that treatment before you leave home and continue it for the duration of your vacation. Coconut is a laxative and bananas are a natural binder. Bear both in mind!

The hotels will use only potable water in the restaurants and for making ice, as well as the making of coffee and washing of vegetables. Make sure you don't have accidents brushing with tap water or consuming shower water. As a rule, avoid all rare or raw protein products, like eggs and shellfish, and if any fish or meat looks suspicious, avoid it since there will surely be something else for you to select. Always go prepared and watch what you eat and watch for symptoms and make sure that you have travel medical insurance. If you have any known plant allergies or interactions, don't try mamajuana (an indigenous drink of the Dominican Republic consisting of a generally unknown combo of bark and twigs [each batch is going to be a bit different so that's why you may not know what's in one compared to another] soaked in rum and red wine and honey). Other than its potency and the fun factor of drinking a lot of it, some people find that they experience an adverse reaction to something in it.

There are lime leaves in the woods that are poison to the skin too so keep your arms and legs in the vehicle if going through the woods on an Outback trip. Just show caution and be smart in all that you do. Know the benefits and reasons why you'd take any medication that you take with you, as well as when it should be administered and when it should be stopped, and get to know the expected side effects. If you have the medical insurance and anything happens that has you worried, go to the resort doctor to set your mind at ease or start treatment. The opinion of a professional who knows about most of what tourists will meet with can be very consoling. They are well used to the symptoms and treatment of various stomach ailments too: the difference between Caribbean food poisoning, the stomach flu and a hangover.