What is the difference between IgE and non IgE allergies?
Immunoglobulin E (IgE) is an antibody present in the blood, usually in small concentrations. When triggered by an allergen (usually proteins in certain food) the body releases antibodies to fight what it thinks are offending cells. This leads to an immediate increase in histamine levels in the body and the classic allergic reactions (such as inflammation of the face and limbs and anaphylaxis). This reaction can be measured by blood tests as there will be an increase of IgE levels in the blood; these are known as IgE allergies.
In non-IgE allergies Some of the same symptoms are experienced in non-IgE allergies, but no antibodies are made against the allergens. There can be a delayed reaction of up to 72 hours after ingestion of the offending food, which means that it is often hard to pinpoint which food is causing the reaction (especially as so much of what we eat nowadays is processed and contains so many ingredients).
What are the difference between food intolerances and non-IgE mediated allergies?
Food intolerance is a general term used to describe a large group of reactions including toxic, metabolic, pharmacologic or other undefined allergic reactions. Non-IgE mediated allergies refer to immunological reactions only, they generally occur over a longer period after ingestion and most often (although not always) affect the gastro-intestinal system.
What are the symptoms associated with non-IgE mediated allergies?
You may experience just one or a combination of multiple symptoms, this can make diagnosis difficult as they overlap with so many other medical conditions.
Anxiety, depression and irritability
Fatigue (from poor absorption of nutrients)
Hyperactivity (in some cases)
Food refusal or food avoidance (an awareness that you may be in pain after eating)
Perianal Redness (especially in babies where allergens excreted by the body stay in contact with the skin and cause a reaction)
Atopic eczema (or dermatitis is an inflammation of the skin which causes itching, reddening, dryness, blistering and scaling - it is not contagious)
Angioedema (swelling of the body)
Erythema (redness of the skin due to inflammation of skin cells often presents itself as a flushed face)
Urticaria (nettle rash or hives made up of red or yellow wheals that look like blisters which are itchy and hot)
Oedema (water retention)
Pruritis (General Itching)
Diarrhoea and/or blood stained or mucous in stools (and dehydration as a result)
Constipation (again due to poor absorption of nutrients)
Crohn’s disease (commonly affects the small intestine, causing inflammation, deep ulcers and scarring to the wall of the intestine)
Vomiting after eating (this is hard to measure in babies as many ‘normal’ babies vomit after feeding and are often diagnosed as having reflux)
IBS or Irritable Bowel Syndrome (common condition of the digestive system)
Leaky Gut Syndrome (the damaged or dysfunctional surface of the gut allows bacteria and other toxins to pass into the stomach)
Indigestion and wind
Low blood sugar
Faltering growth or ‘Failure to Thrive’ (due to poor nutrient uptake by the gastrointestinal system)
Itching of palate and tongue
Glue ear (middle ear fills with glue like substance instead of air, usually a side effect of coughs and colds, allergic people suffer more from these symptoms, so are prone to this condition)
Asthma, coughing and wheezing
How can we diagnose a non-IgE mediated allergy?
Skin Prick Tests/Blood Tests
IgE levels can be tested for through blood tests; but for non IgE-mediated allergies blood tests will come back negative.
Vega Tests and Electroacupuncture (EAV)
Vega machines are a type of electroacupuncture device dating from the 1970s (descendent of the 1950s EAV machines) which practitioners claim can diagnose allergies and other illnesses by measuring electrical pulses in the human body. There have been few clinical studies on Vega Tests and they vary by practitioner. NICE (National Institute for Health and Clinical Excellence, UK) has advised against their use as there is no clinical proof that these machines are effective.
Kinesiology (Muscle Testing)
Developed in the 1960s it relies on energy fields within the body to diagnose allergies and is popular with chiropractors. Although considered to be an inexpensive and immediate form of diagnosis there are few studies done on it and there is poor scientific evidence of its effectiveness.
IgG ELISA Allergy Test
These tests measures IgG and IgG4 antibodies to various foods. Most people develop these antibodies to food they eat and this is a normal non-specific response indicating exposure but not sensitisation; for example high IgG4 levels after cat allergen exposure showed cat allergy protection, not sensitisation.
Elimination Diets and Reintroduction Challenges
This is considered to be the ‘gold standard’ in the UK. There is no cost involved and it is sensitive to all adverse reactions. Although it can be time consuming and there is no way of confirming results, it is widely accepted by doctors as confirmation of a non-IgE mediated allergy.
To help your GP with diagnosis it is commonly advised to keep a food diary and note reactions to certain food. After discussion with your GP and referral to a dietician so that an alternative balanced diet can be agreed, a two to six week exclusion diet can be undertaken (depending on severity of symptoms) after this time you should see the dietician and/or GP and consultant to discuss the next steps for prevention and treatment.
You can read more on how to complete a food diary
How can we prevent and treat a non-IgE mediated allergy?
The causes of allergies are not yet know, so there is no known way of preventing them, but we can avoid what makes us sick and treat the symptoms if we become accidentally exposed to our allergens.
Prevention of symptoms is the same as with normal food allergies, avoidance of food which causes adverse symptoms, taking careful note of ingredients on processed food packages and understanding which ingredients can cause symptoms.
Immunotherapy is becoming more commonplace for food allergies now, expecially for the most common food allergies. You can ask your GP if this is an option for you.
Elimination diets followed by hospital supervised oral food challenges are important in the identification and treatment of an allergy. Food allergies to common allergenic foods such as milk, egg, wheat and soya can be outgrown in childhood; oral food challenges are an important part of the long-term management.
Antihistamines can be given (available on prescription from your GP only, be especially careful with use in babies and young children). Antihistamines will reduce the histamines in the body and help with gastrointestinal, urticaria, angioedema and nose complaints.
Bronchodilators (blue asthma inhalers, again on prescription) can be given to reduce wheezing, coughing and ease any asthma symptoms.
Corticosteroids can be applied to the skin to reduce inflammation and itching, especially in the case of eczema.
If the an allergy blood test has come back negative this does not mean that they do not have a non-IgE mediated allergy instead. Talk to your GP about elimination diets and food diaries.
Try to avoid expensive and unproven tests offered by companies who may only be trying to sell you extra vitamin and mineral supplements.
When dealing with the suspected allergies of babies and children you should be in regular discussion with your GP/dietician/Consultant/Allergist to make sure your child is getting all the nutrients they need for proper growth and development.
Try to get your GP to prescribe anti-histamines, steroids and creams which will improve the symptoms from the allergies until you learn to keep them under control.
Reference and Resources
DermNet NZ - Allergies Explained
NHS - Food Allergy
Babycentre - Reflux
World Allergy- Food Allergy
Chron's and Colitis UK
National Institute for Health and Care Excellence - Food allergy in under 19s: assessment and diagnosis
Guidelines in Practice - Allergy Top Tips
Amino Acid Profiling Identifies Disease-Specific Signatures in IgE-Mediated and Non-IgE-Mediated Food Allergy in Pediatric Patients with Atopic Dermatitis, 2023
Perspectives on Non-IgE-Mediated Gastrointestinal Food Allergy in Pediatrics: A Review of Current Evidence and Guidelines, 2023
Outcomes reported in randomized controlled trials for mixed and non-IgE-mediated food allergy: Systematic review, 2023
Perspectives on Non-IgE-Mediated Gastrointestinal Food Allergy in Pediatrics: A Review of Current Evidence and Guidelines, 2022
Non-IgE/Mixed Food Allergies and Functional Gastrointestinal Disorder: A Common Thread between Childhood and Adulthood, 2022
Protocol for a systematic review of the diagnostic test accuracy of tests for IgE-mediated food allergy, 2021
Non-IgE-Mediated Gastrointestinal Food Protein-Induced Allergic Disorders. Clinical Perspectives and Analytical Approaches, 2021
Non–IgE or Mixed IgE/Non–IgE-Mediated Gastrointestinal Food Allergies in the First Years of Life: Old and New Tools for Diagnosis, 2021
Non-IgE-Mediated Gastrointestinal Food Allergies in Children: An Update, 2020
What do allergists in practice need to know about non–IgE-mediated food allergies, 2019
Non-IgE-mediated food hypersensitivity, 2018
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