The elimination diet and food challenge test are used to identify food allergies. The elimination diet involves removing specific foods or ingredients from your diet that you and your doctor suspect may be causing your allergy symptoms. (Common allergy-causing foods are milk, eggs, nuts, wheat, and soy.) Your doctor will supervise this diet over two to three weeks.

During this time, you will need to carefully read food labels and find out about food preparation methods when dining out. You'll also need to keep a food diary to record the foods you are eating. If you remove a certain food and the symptoms go away while following this diet, your doctor can usually identify that food as the cause of your problems.

While following this diet, make sure you are eating other foods that provide the same nutrients as those you've eliminated (for example, try tofu-based foods instead of dairy products). A dietitian can help you plan meals that are healthful and nutritious without including the potentially allergenic foods.

After following the elimination diet, your doctor will ask you to gradually reintroduce the foods you were avoiding into your diet, one at a time. This process helps link symptoms to specific foods.

You will need to carefully record any symptoms that occur when you eat each of these foods. If your symptoms return after eating the food, the diagnosis can usually be confirmed. You will be asked once again to eliminate the foods that have been identified as causing symptoms to see if the symptoms clear up.

This is not a foolproof method. Psychological and physical factors can affect the diet's results. For example, if you think you're sensitive to a food, a response could occur that may not be a true allergic one.

Before making significant changes in your diet, always seek the advice of your doctor. If you randomly remove foods from your diet, you may not have a balanced diet -- and a lack of some nutrients can cause other health problems. You may also become frustrated because it may seem that everything you eat is causing a reaction.

If you've had a severe (anaphylactic) reaction to certain foods, this method can't be used.

What Is a Controlled Food Challenge?

In a controlled environment such as an intensive care hospital unit, the doctor (usually a board-certified allergist) may conduct a food challenge test to determine if a food allergy exists or to confirm a suspected food allergy.

A sample of the suspected offending food is given to the person unknowingly. The suspected offending food may be mixed with another food or may be disguised as an ingredient in another food. These food preparation techniques are used to prevent undue influence on the outcome of the test (if the person recognizes the food by sight or taste). Another method is to have the person take a capsule containing the allergen.

This test is given under strict supervision. After eating the food or taking the capsule, the person is monitored to see if a reaction occurs.

The ideal way to perform the food challenge test is as a "double-blind, placebo-controlled test." With this method, neither the allergist nor the allergy sufferer is aware of which capsule, or food, contains the suspected allergen. In order for the test to be effective, the person must also take capsules or eat food that does not contain the allergen. This will help the allergist make sure the reaction, if any, being observed is due to the allergen and not some other factor.

Someone with a history of severe reactions cannot participate in a food challenge test. In addition, multiple food allergies are difficult to evaluate with this test.

Since this test takes a lot of time to perform, it is costly and thus, done infrequently. This type of testing is generally used when the doctor needs to confirm or eliminate specific food allergens.

Reviewed by the doctors at The Cleveland Clinic Department of Pulmonary, Allergy and Critical Care Medicine.

Edited by Charlotte E. Grayson, MD, Feb. 2004, WebMD.

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