How Will My Doctor Know If I Really Have A Food Allergy?

Shortly after eating strawberries you feel your tongue getting tingly, should you be concerned? Or perhaps your son gets stomachaches after eating his whole grain waffles every morning and you can't make any sense of it.  While symptoms can range from things like headaches and hives, to upset stomaches, runny noses and more serious issues like difficulty breathing, none of them should be ignored. Having a food allergy is a serious matter than can be life threatening. For many people who experience reactions the second exposure can be worse than the first. For all of these reasons, anyone who may potentially have a food allergy should seek medical attention immediately.  

It is estimated that at least 15 million people have food allergies. This can affect everyone from infants to seniors. And in fact someone can develop a food allergy at any stage of life.  While some allergies can be outgrown, others cannot. The 8 most common food allergens, which include milk, wheat, peanuts, tree-nuts, crustacean shellfish, soybeans, fish and eggs, account for over 90 percent of food allergies.  However, make no mistake there are allergies to many other foods that cannot go unnoticed.  Whatever the food allergy, it is something to take seriously.   

The first step to understanding your symptoms and food allergies is meeting with your doctor or allergist.  Depending on your symptoms, your doctor will determine the best course of action to diagnose your allergies. There are many tools and methods that the doctor will use to conclusively determine which foods or substances are causing your allergic symptoms.  Once confirmed, you will be able to focus on removing the food allergen from your diet, relieving you of the symptoms caused by this allergy.  This will enable you and your loved ones to lead a safe, healthy and nutritious life.

Below are the most common tools and methods that the doctor will use to identify food allergies.

​Edited by Marlo Mittler, MS RD

1
History

Your first visit to the doctor to discuss your allergy symptoms will probably begin with a physical examination and a history. If possible keeping a food diary, along with any suspected symptoms, can be helpful to bring to this appointment. Your physician may ask you when your symptoms began, what sorts of foods you ate around the time they started, and what changes you may have experienced in your environment.

In almost all cases, your doctor will supplement the history with diagnostic testing. The history can help allergists pinpoint potential allergens to focus on, or to choose which testing methods might be most appropriate.

2
Prick Tests

Allergy
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A prick test, or scratch test, is often used to test a number of potential allergens at one time. The allergist tests a number of allergens on the thin skin of the forearm or the back. A drop of a solution with the food allergen is placed on the arm. The allergist scratches the skin to allow for a very minimal amount of the solution to enter just below the surface. A positive test will show as a hive, or wheal.  A wheal is a raised white bump surrounded by a circle of itchy skin.  An inconclusive prick test will usually be followed by a more sensitive test. All testing is done within the doctors office, under close supervision, in the case of a serious life threatening reaction occurring. 

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3
RAST Tests

Taking blood sample
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The RAST, or radioallergosorbent, test is a blood test that tests for IgE antibodies. It is often used in circumstances when a skin test would be difficult to perform (for example, in a patient with severe eczema or another skin condition) or where exposing the patient to an allergen might be unnecessarily risky (for example, in cases of suspected severe peanut allergies). A positive test result indicates that the body has produced antibodies to an allergen and is primed for a reaction.

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4
Elimination Diet

An elimination diet can be undertaken in several ways, depending on the allergist supervising it, but the basic principle is the same: the diet begins with a limited set of foods that are deemed unlikely to cause a reaction. Other foods are added one by one over a period of days or weeks. While the elimination diet can be tedious, it can be an effective way to determine which substances are problematic when skin testing is inconclusive. It can also help diagnose food intolerances, which may cause problematic symptoms but will not show up on an allergy test.

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5
Oral Food Challenge

An oral food challenge is risky and always carried out under close medical supervision, but will conclusively show the presence of an allergy. In a food challenge, patients ingest suspected allergens and are observed over a number of hours to determine whether they have an allergic reaction.

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