Food Allergy Living Blog Tagged Results

In food allergy circles, we usually think of symptoms and side effects as results of food allergies, not the other way around. In most cases that’s true. Science has shown a strong link between food allergy and atopic dermatitis, a form of eczema. Last month Dr. Jon Hanifin, a respected dermatologist, gave a talk to colleagues discussing the link between atopic dermatitis and food allergies. The research he presented suggests that for some patients it may actually be atopic dermatitis that comes first and acts as a precursor to food allergies.

Atopic dermatitis is often one of the first signs that a parent or caregiver notices in their child which helps lead to the diagnosis of food allergy. As Dr. Hanifin explained, about 6-10% of children are diagnosed with atopic dermatitis, and of those about a third will be diagnosed with a food allergy. Which begs the question: If parents notice signs of atopic dermatitis first, and an allergy diagnosis comes later, couldn’t atopic dermatitis be causing some instances of food allergy?

What We Know:

-In cases of food allergy, offending foods cause reactions in the body which involve the immune system

-Immunoglobulin E antibodies (IgE) are immune substances which are normally in our bodies at low levels, but are higher with food allergy

-Allergy symptoms often involve the skin (including our digestive tract, which is like an inside skin), an important barrier that keeps most outside “things” from getting inside

-One factor of atopic dermatitis is “holes” in the barrier our skin provides

What Dr. Hanifin Proposed:

In the past it was assumed that food allergies came first, causing both high IgE levels and atopic dermatitis. Dr. Hanifin suggested that in some patients atopic dermatitis is caused by “gaps” in the skin (likely due to genetics), which means that foreign substances can enter the skin and cause adverse reactions. He thinks it may be proteins that get through these gaps which allows the body to become sensitive to certain foods, leading to a food allergy.

What does all of this mean? The biggest message here is that patients with atopic dermatitis, especially those under five years, should be tested for food allergies. While avoiding food allergens may not help improve atopic dermatitis, it could certainly prevent or improve other serious side effects of allergies. The second message is that more research needs to be done into the causes of atopic dermatitis and its relationship to food allergies. Any research that leads to better health, through reducing instances of atopic dermatitis and/or food allergies, is good research! Tell us about your experience: Was atopic dermatitis the first sign that you saw of your child’s food allergy?

- Rob

In December 2010, the National Institute of Allergy and Infectious Disease (NIAID) released an Expert Panel Report on the Guidelines for the Diagnosis and Management of Food Allergy in the United States. You are able to view the full report or the summary (I would suggest the summary as the full report is lengthy). I will mention a few of the guidelines to give you an understanding of the report, but feel free to download the report for yourself so you may be updated on the latest guidelines for food allergy (FA) that many healthcare professionals will be referring to.

The report notes that multiple studies have found 50-90% of presumed food allergies are not actually food allergies! I couldn’t believe as high as 90%! For this reason, I will briefly review the diagnostic recommendations.

Diagnosis of IgE Mediated Food Allergy (Reactions are seen in a short time frame.)

The Expert Panel (EP) stresses the importance of confirming a food allergy. In order to confirm the diagnosis of a FA, it is important the doctor perform a medical history and physical examination. In order to identify the food causing the allergies, the EP recommends a doctor perform a skin prick test (SPT). It is important to note that a SPT alone cannot be considered a diagnosis of FA. The EP does not recommend using tests such as intradermal testing, routine use of total serum IgE and atopy patch tests. Interestingly, they suggest food elimination diets as a useful tool for diagnosing FA. It is also recommended for doctors to use oral food challenges to get a FA diagnosis. It is the gold standard for ruling out certain foods.

Diagnosis of Non-IgE Mediated Reactions (Also known as delayed reactions)

In order to diagnose Food Protein-Induced Entercolitis Syndrome (FPIES,) the EP recommends using medical history and oral food challenges. It was noted that when the causative food is removed and the symptoms subside, it may be enough for an FPIES diagnosis. Doctors and families must work closely together to get the best results for their patients.

The report also mentioned that to reevaluate a patient with a food allergen whether its annually or at another interval will depend on the foods in question, the age of the child and the current medical history.

I very much encourage you to read over the guidelines yourself. The more educated we all are, the more we can help each other and your family to ensure those with food allergies are getting the proper treatment for the accurate food allergy diagnosis. Let me know once you have read it, what you think! You can even share this with your doctor.

-Christine

Question: What is the difference between immediate and delayed allergic reactions? We are trying to get to the bottom of what foods are causing my son’s allergic reactions and I think that he may be having a delayed reaction to something.

Answer: Immediate allergic reactions, also known as IgE reactions, occur within a few moments of exposure to an allergen to up to two hours, so it is easy to identify which food is causing the reaction.

Delayed allergic reactions (which are non-IgE) can happen anywhere from two to 72 hours after exposure to an allergen, or longer. This can make it difficult to pinpoint what is causing a reaction. Plus, there are no specific lab tests to identify non-IgE allergies so the only way to know if a food is safe or not is through trial and error. It might be helpful to keep a food journal of exactly what your son eats and when. Then you can look for patterns over time, and hopefully figure it all out!

If you’re still having trouble identifying the problem foods, your doctor may recommend an elimination diet. With an elimination diet, all foods are taken out of the diet and an elemental formula, such as Neocate and/or E028 Splash, is the sole source of nutrition. This period allows the symptoms to resolve and sets up your “baseline”. After a few weeks, foods are added back to the diet one at a time. Since the reactions are delayed, you should wait a few days after each food introduction to see if symptoms return. If no symptoms occur, you move on to the next food. If symptoms do occur, you can add this food to the no-no list and continue with this process (remember that there may be multiple foods responsible so you have to contrinue with the process of trying foods one at a time).

Many Neocate parents know that using allergy testing to determine food allergies can be tricky, because many children experience what may be considered a food intolerance or sensitivity, versus a true food allergy. 

Generally, a food allergy is considered to be an immunoglobulin E (IgE) mediated immune response.  (1) In a previous blog, we have outlined the standard tests that may be done to determine whether your child has an Ig-E mediated food allergy, such as a skin prick test or a RAST.

However, you or your child may have a negative IgE test, but still appear to have symptoms that are typical of a food intolerance or sensitivity.  Several tests are now marketed as tools for determining these types of non-IgE mediated food reactions.  While more research is needed to determine the accuracy of these tests, they may provide helpful clues as to which foods to consider eliminating from the diet. Some of these tests include:

Enzyme Linked Immunosorbent Assay (ELISA): A blood test that is intended to measure levels of immunoglubulin G (IgG) in response to different foods.  However, elevated IgG does not always indicate an adverse food reaction.  In fact, sometimes elevated IgG is an indicator that an IgE response, or a true allergy, has been successfully treated.  This test may be helpful in providing clues as to which foods to consider eliminating, but remember that elevated IgG does not always mean that there is a negative reaction to the food.  (2, 3)

Mediator Release Testing (MRT): A blood test that in intended to measure many types of non-Ig-E mediated food intolerances or sensitivities, including IgG response.  Proponents of MRT believe that because it assesses multiple immune pathways it provides a more complete picture of which foods are causing symptoms compared to IgG testing.  (3)

Atopy Patch Testing (APT): A skin test used to determine delayed food reactions.  A preparation of the food is placed in an aluminum chamber on the skin for 48 hours. Twenty four hours after removal the skin is inspected for a reaction; a positive reaction is determined based on the level of redness and swelling.  (1) Some practitioners find that APT is a great tool to use along side IgE testing in order to a get a more complete picture of all the foods that may be causing symptoms for you or your little one.

Have you tried any of these tests?  We would love to hear about your experience! 

References:

1. Carney, Liesje Nieman. (2009, July). Pediatric Food Allergies. Today’s Dietitian, 11, 48.

2. Joneja, Janice Vickerstaff. (2008, January). Food Allergies: Type II, III, and IV Hypersensitivities. Today’s Dietitian, 10, 10.

3. Keller, Maura. (2010, August). Get Certified- Provide a Valuable Service By Adding Allergy Testing to Your Practice. Today’s Dietitian, 12, 18. 

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