Allergies: Elimination Diet and Food Challenge Test

The elimination diet and food challenge test are tools 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 include milk, eggs, nuts, wheat and soy.) Your doctor will supervise this diet over a few 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.