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Diagnosis & Specialist Care of Allergy & Clinical Immunology - Since 1982
All About Food Allergies.
Food allergies usually present themselves in childhood, but they can also develop later in life. At the London Allergy Clinic, we focus on providing clear, accurate information, testing and diagnosis for food allergies.
Understanding Food Allergies
A food allergy occurs when the immune system reacts to a food protein as if it were a harmful invader. This response can cause symptoms which range from mild to life-threatening. It is important to know and understand the difference between these for the effective testing and diagnosis of the allergy.
Allergies are also different from food intolerances. While allergies usually trigger an immediate reaction (or within an hour), intolerances may take several hours, or even a day, to appear.
The majority of food allergies are 'IgE-mediated' meaning it is immunoglobulin E, an antibody that forms part of the immune system, which triggers the release of histamine and stimulates the allergic symptoms.
Some allergies, and intolerances, are non-IgE mediated and are more difficult to test and diagnose as a result. Read more below about testing options.
Common Food Allergens
Some of the most common food allergens include:
Nuts
(E.g cashew & hazelnut)
Soya
Milk
​
Shellfish
(E.g shrimp, lobster or crab)
Eggs
Fruits
(E.g apple, kiwi or peach)
Wheat
Seeds
(E.g sesame & sunflower)
Vegatables
(E.g potato, celery or carrot)
Symptoms of Food Allergies
Symptoms of food allergies can range from mild to severe, depending on the individual and the allergen involved.
If any airway or breathing problems are noted during an allergic reaction, or if anaphylaxis is suspected, it is important to call for an ambulance immediately and use your EpiPens (if prescribed).
Common symptoms include:
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Tingling or itching in the mouth or throat
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Swelling of the lips, tongue, or throat
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A sensation of the throat closing
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Difficulty breathing
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An itchy rash
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A sudden drop in blood pressure
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Gastrointestinal symptoms, such as vomiting and abdominal pain
Reliable Testing Methods
To diagnose food allergies there are two main testing methods: skin prick tests and specific IgE blood tests. These tests identify the presence of IgE antibodies, which indicate sensitisation to specific allergens. However, a positive test alone doesn't confirm an allergy. A clinical history and possibly further testing are necessary to establish a diagnosis.​
There is no reliable test available for a non-IgE mediated allergy, or most food intolerances. A diagnosis will usually be reached once an IgE-mediated allergy has been ruled out, and by using trials of elimination and re-introduction diets managed by your doctor.
Unreliable Testing Methods
There are numerous unscientific, unproven testing methods available, particularly online.
These tests are worrying because they can produce a misleading result which patients act upon. Some patients start unnecessary elimination diets as a result of a bad test, which can lead to nutritional deficiencies and other health issues, for example conditions like scurvy or compromised bone health.
Furthermore, once a food group has been eliminated from a diet, it can decrease the body's tolerance to that food, so, when it is reintroduced it could make a potential reaction more severe.
Examples of Unreliable Tests:
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IgG Testing
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Kinesiology
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Homeopathy
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Cytotoxic Food Testing
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Hair Analysis
Management and Treatment
The primary approach to managing food allergies is avoidance of the identified allergen. This requires accurate testing and diagnosis to ensure the right foods are appropriately eliminated. In certain cases, desensitisation therapy may be an option, however, this should be done under the careful guidance of an appropriate clinician in a hospital setting.
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