Many people report having a food allergy and are keen to try an allergy test to get a diagnosis. But, exactly how do you get an accurate allergy test?
This article will discuss the common symptoms of food allergies and how you can get an accurate test.
Table of Contents
Food allergy symptoms
Food allergy symptoms can be anaphylactic but can also involve digestive symptoms such as diarrhoea and constipation. Symptoms may also include eczema and skin problems.
What is a food allergy?
When an individual has a food allergy, their body mistakenly creates antibodies (IgE – antibodies) in response to coming into contact with that food. This can then result in the symptoms described above.
How common is a food allergy?
The World Health Organization estimates that 10 – 40% of the global population has a food allergy (1).
Luckily, we know that allergies are less common in adult years (2).
There are multiple food allergy tests on the market which are inaccurate and considered fads.
The following tests should be avoided:
- Alternative blood tests (leukocytotoxic tests) – detects food allergies when white blood cells (leukocytes) swell when mixed with the allergen.
- Basophil histamine release/ activation – a food allergen stimulates white blood cells (basophils) in a test tube.
- Endoscopic allergen provocation – an allergen is inserted into the colon. The mucous membrane is examined for an allergic response.
- Facial thermography – to examine the effects of antihistamine on the skin of the nose.
- Gastric juice analysis – suspected food allergen is ingested. A feeding tube is used to gather some gastric juice from the stomach to be examined.
- Hair analysis – Energy fields of a sample of your hair are sent to a lab where they are scanned.
- IgG/IgG4 testing – checks for immunoglobulin G (IgG), an antibody created by your body to fight a particular allergenic food
- Kinesiology testing – This is based on how certain foods can cause an energy imbalance in your body. Your muscle response is tested by holding the suspected allergen in a container.
- MRT test and LEAP protocol – MRT (mediator release test) is a blood test that quantifies how strongly your immune cells react to foods. LEAP (lifestyle eating and performance) is an eating plan based on your MRT results.
- Provocation neutralization – allergen is injected under the skin or placed under the tongue to provoke stimulation.
- Electrodermal (Vega) testing – This measures the electromagnetic conductivity in your body. The offending food will show a dip in the electromagnetic conductivity.
Ways to get a food allergy diagnosis
Food allergy diagnosis is complicated and varies in method depending on what type of allergy you have.
IgE & mixed-type allergies
IgE-mediated food allergies can result in an immediate reaction within a few minutes to 2 hours. They are often caused by foods such as (5):
The body reacts to the food allergy and produces allergen-specific immunoglobulin E (IgE) antibodies in the bloodstream (6).
Some people can suffer from both IgE and non-IgE-mediated allergies. This is known as a mixed-type allergy. Examples include atopic dermatitis and eosinophilic esophagitis (EoE) (7).
You can read more about eosinophilic esophagitis here.
Diagnosing IgE & mixed-type allergies
The gold standard for testing for these types of food allergies is a complicated 3 step process. This process involves medical testing, doctors’ assessment and a specialist diet.
Medical and symptom history (by a specialist doctor)
A food allergy has specific patterns, which a specialist doctor can check from your medical history. They will also rule out other possible causes of your condition.
The blood test or skin prick test only shows an ‘allergic sensitisation’ but not necessarily an allergy (5).
An allergen-specific IgE serum blood test or skin prick test
This testing shows that an immune reaction may be present.
Food exclusion diet followed by reintroduction to confirm the diagnosis
You firstly avoid the suspect food for a set amount of time, following be a reintroduction period. This further improves the accuracy of the overall diagnosis (6).
Depending on your food allergy symptoms, your doctor may advise you to follow a reintroduction protocol in a clinical setting in case of anaphylaxis.
Diagnosing Non-IgE mediated food allergies
Some food allergies fall under the category of ‘non-IgE mediated’ such as cow’s milk protein allergy. This type of allergy is more likely to be undiagnosed during childhood and adulthood.
The best way to diagnose these is through a medical history, symptom evaluation and exclusion diet (7). Non-IgE mediated allergies are often indicated in those with delayed reactions, which can take up to several days or who appear to have no pattern in their symptoms.
What is an elimination diet?
An elimination diet is when one or several allergens are excluded from an individual’s diet for a set period. This is not a diet for life but more of a way to diagnose. After this, the food challenges/reintroduction phase is when you confirm your allergy.
It is important to note that you must NOT attempt this diet alone.
Missing out on expert help can mask an underlying medical condition such as coeliac disease, which is not an allergy. This can lead to nutritional deficiencies in the long term that can otherwise be prevented.
Food allergies are increasingly common and can result in symptoms similar to other conditions like IBS. Allergies can be categorised into 3 types such as IgE, non-IgE and a mixture of both. Their diagnosis and treatment plans are different, so it is important to work with an allergy specialist.
Alternative allergy tests should be avoided as they lack scientific evidence. They can be expensive, and you may be unnecessarily restricting foods in your diet.
Safety Note: If you think you have an allergy, you must report this to your GP. They will get you on the correct path to a safe diagnosis. Attempting to tackle an allergy on your own may result in death, as some reactions are life-threatening.
Updated by Leeona Lam MSc, ANutr (2022), reviewed by Serena Bansal Registered Dietitian BSc Hons and Kirsten Jackson Consultant Dietitian BSc Hons, RD, PG Cert
Kirsten Jackson is a UK registered Consultant Gastroenterology Dietitian and founder of The Food Treatment Clinic. She has undergone many qualifications to get where she is today, including a UK BSc Honours Degree in Dietetics and Post-Graduate Certificate in Advanced Dietetics. In addition to this, she has FODMAP Training from Kings College London University. Kirsten set up The Food Treatment Clinic in 2015 after first experiencing digestive problems herself. She felt that the NHS was unable to provide the support individuals needed and went on to specialise in this area before opening a bespoke IBS service. Kirsten also participates in charity work as an Expert Advisor for the IBS Network. In addition, she can be seen in publications such as Cosmopolitan and The Telegraph discussing IBS as an Official Media Spokesperson to the IBS Network.