A true food allergy is not as common as you may actually think. Food sensitivities/reactions, which are much more common in my experience, are often mistaken for allergies. A true allergy to food is mediated by the immune system, and involves an antibody reaction to a specific food or drink. Food allergies are categorized into groups, and for this purpose I’m focusing on two of those: Type 1 immediate response (IgE) and Type 3 delayed response (IgG).
Type 1 or IgE Response (Immediate Food Allergy)
The best known and most studied form of food allergies is called a Type 1 immune reaction, or IgE mediated response. An IgE reaction occurs immediately after exposure to the allergen. With this allergy, the immune system creates an antibody called IgE (Immunoglobulin E) that attacks certain foods, causing a reaction. Type 1 food allergies occur in less than 5 percent of the population, and mostly in children. These type of allergies usually occur in the genetically predisposed individual (one or both parents have an allergy).
Since this pathway occurs immediately, it is often easy to recognize a Type 1 allergy. This is the immunological pathway behind seasonal allergies such as hay fever. The most common test for this type of reaction is the RAST (radioallergosorbent) or “scratch” test which is performed by doctors or specialists. This involves scratching the skin and applying a test substance and then waiting for a “wheal and flare response,” often a skin reaction.
The problem I find with this test is that it’s not always a reliable indication of an allergy, with many patients showing a “false negative” test and at times even an exaggerated positive response. The test substance may be too old to invoke a reaction or the test substance may not specific enough to the particular person and therefore does not invoke the reaction. There are simply too many reasons why this test can fail.
Type 1 Food Allergy Symptoms
The allergen and resulting symptoms are unique to the individual, so symptoms can vary by person. However, some people don’t have any idea that they have a food allergy. Not long after the response, allergy symptoms become apparent, including swollen hands, itchy and swollen eyes, sensations of the lungs, and in severe cases closing of the larynx or throat. Anaphylaxis is the most alarming response (difficulty breathing, fast heart rate, panic) and other symptoms may include stomach cramping, diarrhea, hives, swelling, itching and skin rashes.
Type 1 Food Allergy (IgE) Summary
-Generally no more than one or two foods are involved in causing these allergic symptoms.
-Even the tiniest trace amounts of food can trigger this intense allergic reaction.
-Allergic symptoms commonly appear within 2 hours after consumption, but may occur within minutes.
-Primarily affects the skin, airway and digestive tract manifesting in conditions such as asthma, rhinitis, urticaria, angioedema, eczema, vomiting, diarrhea and anaphylaxis.
-This type of allergy is usually a permanent, fixed food allergy.
-Frequently IgE responses show as positive on “RAST” and skin tests, but this is not always the case. Variables include the experience of the person doing the testing, the conditions the test was performed under, and if the patient was taking drugs (like antihistamines) beforehand.
-Although mixed immediate/delayed onset allergic reactions have been reported (e.g., eczema), the IgG antibody is not characteristically involved in IgE responses.
-Mast cells, basophils, histamine and tryptase release are all commonly involved in this type of reaction.
Type 3 or IgG Response (Delayed Food Allergy)
Non-IgE-mediated allergies involve antibodies like IgG (Immunoglobulin G). Symptoms of an IgG-dependent reaction may occur hours–even days–following exposure to the allergen. When foods are involved, these are often referred to as “delayed food reactions”. The IgG antibody may bind to the food antigen and form an immune complex, and these complexes may deposit in various tissues and trigger inflammatory reactions. It is most unfortunate, but conventional medicine often does not recognize these types of immune responses.
Delayed Food Allergy (IgG) Summary
-Anywhere from 3 to 10 food allergens may be involved, and in some cases up to 20 foods have been reported.
-It is more rare for a person in this category to be only allergic to one or two foods.
-Unlike IgE allergies, larger amounts of food often in multiple feedings are commonly needed to provoke these types of allergic reactions. Reactions may not occur after a single food challenge.
-Virtually any tissue, organ, or system of the human body can be affected, making it difficult to distinguish between an IgE and IgG response.
-It has been estimated that addictive cravings and withdrawal symptoms can be clinically significant in 20-30% of patients suffering from this type of allergy.
-The offending foods are rarely self-diagnosed. Multiple doctor visits involving different physicians are often the rule, not the exception, before proper diagnosis and treatment is provided.
-Allergic foods are commonly favorite foods, eaten often and in larger amounts.
-Unlike IgE responses, IgG responses are often alleviated or reversed.
-IgG responses typically show as negative on RAST and skin tests.
-Sensitized lymphocytes, eosinophils, platelets, release of PAF and leukotrienes may be more prevalent.
For more on food allergies, check out our blog on Food Allergies, Sensitivities and Adrenal Fatigue and Making Sense of Food Allergies, Sensitivities and Intolerances
Image Credits: Hives on back by DLdoubleE (Own work) [Public domain], via Wikimedia Commons
About the Author: Eric Bakker B.H.Sc. (Comp.Med), N.D, R.Hom. is a highly experienced naturopathic physician who has been in clinical practice for 25 years. Eric is passionate about improving people’s lives through proven wellness and lifestyle principles, natural medicine practice as well as public and professional practitioner education. Eric specialises in candida yeast infections, as well as adrenal fatigue, and thyroid disorders. Dr. Bakker has written one of the most comprehensive books on yeast infections called Candida Crusher. Website: candidacrusher.com You can complete his online survey to determine if you have a yeast infection here, or link through to his many YouTube videos: www.yeastinfection.org Dr. Bakker’s Blog: www.ericbakker.com