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Identifying Food Allergies, Sensitivities, and Intolerances


March 28, 2012 | Published by

food allergy test by Flickr user brooke bina

In part 1 of this blog, “Making Sense of Food Allergies, Sensitivities, and Intolerances,” I explained the various ways you may be sensitive, allergic or intolerant to specific foods and how these can impact your health and put additional stress on your adrenals. In Part 2 below, I will help you understand some ways to identify them, and in my next blog, Part 3, I’ll show you how to eliminate them.

IgE Food Allergies – The Usual Suspects

In order to overcome any type of food reaction, you must first identify which foods are causing problems. Eight foods are responsible for approximately 90% of food allergies: shellfish, milk, egg, wheat, peanut, tree nuts, fish, and soy. In the case of the “typical” food allergy it is usually easy to identify a problem if you ingest the food. One bite can cause an immediate allergic reaction.  These allergic reactions are known as IgE mediated allergies or immediate hypersensitivity reactions. IgE refers to the type of antibody produced by the immune system in response to the allergen. Antibodies are the immune cells your body makes against something your body identifies as “foreign.”

Because this type of reaction can be severe, it is preferable to determine IgE allergies without actually eating the food in question.  IgE allergies can usually be discovered via a skin prick test by an allergist. A tiny amount of the food is applied to pricked skin. A positive test causes a red wheal (hive). This test is very sensitive, but not very specific. That means that sometimes someone will react to the test for a food when they actually are sensitive to a related food. For this reason, it’s important to use this test along with a thorough diet history and only test relevant foods. Also, there is a small chance that someone could have a severe allergic reaction to the test foods.

A possible alternative is to test for IgE allergies via a blood test, called a RAST test, and avoid the possibility of a dangerous allergic response. Just know that these are fairly expensive, aren’t as sensitive, are not available for all foods, and typically need to be confirmed by eating the foods in question and looking for a response. (Because IgE mediated responses can be dangerous, it is best to do this under the care of a physician.)

In the case of food sensitivities in which an immune reaction results from antibodies other than IgE, there are different lab tests that can be done. Typically these test IgG or IgA antibodies. IgG is the main antibody in the blood while IgA is the primary antibody in the digestive and respiratory tracts. Typically IgA and IgG food allergy tests involve adding a drop of your blood to food antigens (the protein portion of the food to which the immune system reacts) and looking for a reaction. The IgG test is more sensitive (it can detect the correct antibodies more easily) but less specific (it sometimes detects the wrong antibodies). The IgA test is more specific and less sensitive.

If you decide to do these tests, it is very important that you have been eating the foods you’re testing for roughly 6 weeks or longer before you have your blood drawn. Your body does not make antibodies against an antigen (the food in this case) unless it is exposed to it. So even if you are reactive to a food, after you haven’t eaten it in a while your antibody levels will go down – wonderful news when treating the condition, but problematic when testing. Unfortunately, these tests are also relatively expensive, not always reproducible, and the results on paper don’t always correlate with the symptoms you experience.

Celiac Disease

In celiac disease, an autoimmune disorder, a very specific type of immune reaction occurs. The body creates antibodies against certain proteins found in wheat and other grains, and these antibodies then attack the body’s own intestinal cells mistaking them for foreign cells (auto=self: autoimmune = immunity against self).  Historically, a biopsy of the digestive tract has been considered the gold standard for diagnosing celiac. Now there are lab tests which some physicians feel can predict celiac as accurately as a biopsy if used in conjunction with a food challenge. The most commonly ordered tests are for anti-gliadin antibodies (antibodies against a specific portion of the gluten protein) and tissue transglutaminase antibodies (antibodies that attack the intestinal cells).

These same tests can sometimes be useful in looking for gluten sensitivity unrelated to abdominal or intestinal problems, but there are limitations. One of the primary problems is that there are many proteins on the grain in addition to those that we know cause celiac disease, and lab tests aren’t available for most of them. If you are reacting to a protein in the grain other than the few we have a test for, nothing will show up on the lab test.

Testing for Food Intolerances

For food intolerances there are sometimes tests available. For example, in the case of lactose intolerance, there are two common tests. Each begins with drinking a liquid with high levels of lactose. In one, blood sugar levels are measured after a couple hours. If your blood sugar doesn’t rise, you aren’t breaking down and absorbing the milk sugar. In the other test, the amount of hydrogen you exhale is measured at regular intervals for up to 3 hours after drinking the liquid.

Typically, people don’t exhale a large amount of hydrogen, but if you are not absorbing the lactose, the milk sugar gets broken down by colonic bacteria that create a lot of hydrogen and other gases (one of the main reasons lactose intolerance is so painful!). Lab tests don’t exist for every food intolerance though, or for most of the sensitivities related to the drug-like components in food. In the case of caffeine, sometimes an elevated heart rate or blood pressure will let you know that you are sensitive to the stimulant effects, but for many pharmacological components, there is nothing easily measurable.

If you’ve been reading closely, you may have noticed some patterns emerging:  although many lab tests exist and can prove useful, none is 100% accurate, most are fairly expensive, and there are many situations for which we don’t even have lab tests. This is why in my practice I encouraged my patients to do an elimination and challenge diet rather than a laboratory test (except in the case of IgE mediated allergies). The diet is much less expensive than the labs; will help detect various types of food reactions- allergies, sensitivities, intolerances, and reactions to pharmacologically active food constituents- and it is the first step in treatment as well. Stay tuned for the next blog in which I describe how to do the elimination and challenge diet.

Continue to part 3 – Eliminating Food Allergies, Sensitivities, and Intolerances

Read part 1 – Making Sense of Food Allergies, Sensitivities and Intolerances

Dr. Lise NaugleAbout the Author: Dr. Lise Naugle is an associate of Dr. James L. Wilson. She assists healthcare professionals with clinical assessment and treatment protocols related to adrenal dysfunction and stress, and questions regarding the use of Doctor Wilson’s Original Formulations supplements. With eleven years in private practice and a focus on stress, adrenals, hormonal balance and mind-body connection, she offers both clinical astuteness and a wealth of practical knowledge. Dr. Naugle also maintains updated information about the latest scientific research on the hypothalamic-pituitary-adrenal axis function, endocrine balance and nutritional support for stress and develops educational materials about stress and health for clinicians and their patients.

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