A food allergy blood test is used to detect immune responses to specific foods by measuring levels of Immunoglobulin E (IgE) antibodies in the blood. When someone has a food allergy, their immune system mistakenly identifies certain food proteins as harmful, triggering the production of IgE antibodies. These antibodies cause allergic reactions ranging from mild to severe symptoms.

How Food Allergy Blood Tests Work

  1. Blood Sample: A blood sample is taken from the patient and sent to a lab.
  2. IgE Detection: The lab tests for specific IgE antibodies against various food proteins. The higher the level of IgE, the more likely it is that the person is allergic to that food.
  3. Results: The results are often reported on a scale (Class 0 to Class 6), with higher classes indicating a stronger likelihood of an allergic response to the tested food.

Types of Food Allergy Blood Tests

  1. Specific IgE (sIgE) Testing:
    • Measures the amount of IgE antibodies in the blood to particular food allergens.
    • Commonly tested foods include:
      • Dairy: Cows Milk
      • Eggs: Egg whites and egg yolk
      • Nuts & Seeds: Peanuts, Sesame
      • Finfish: cod
      • Soy: Soybeans and soy-based products
      • Wheat: Gluten-containing products
      • Fruits/Vegetables: Kiwi
      • This is the most widely used method for diagnosing food allergies.
  2. Component-Resolved Diagnostics (CRD):
    • A more advanced type of testing that identifies specific protein components within a food allergen that may be causing the allergy.
    • Helps in determining whether a person is allergic to a specific protein in a food or whether there might be cross-reactivity with other allergens.
    • For example, in peanut allergy testing, CRD can identify whether a person is allergic to Ara h2, a peanut protein associated with severe reactions.
  3. Total IgE Testing:
    • Measures the overall level of IgE in the blood.
    • A high total IgE level suggests an allergic tendency but does not specify the allergen.
    • This test is often used as part of a broader assessment of allergic conditions, such as asthma or eczema.

Interpreting Food Allergy Blood Test Results

  • Class 0: No detectable specific IgE to the food; unlikely to have an allergy.
  • Class 1: Low levels of IgE; possible mild allergy.
  • Class 2-3: Moderate levels of IgE; likely allergic with noticeable symptoms.
  • Class 4-6: High to very high levels of IgE; strong likelihood of severe allergic reactions.

It’s important to note that having elevated IgE levels doesn’t always guarantee clinical symptoms of an allergy. A person may have detectable IgE antibodies but not react when they eat the food. The clinical history of the patient (symptoms experienced after consuming the food) is crucial for interpreting the results.

Conditions Detected by Food Allergy Blood Tests

  • IgE-Mediated Food Allergies: These include immediate allergic reactions like hives, swelling, anaphylaxis, gastrointestinal symptoms, and respiratory issues.
  • Oral Allergy Syndrome (OAS): A mild food allergy caused by cross-reactivity between pollen and certain fruits or vegetables.
  • Exercise-Induced Food Allergy: An allergic reaction triggered when a person eats certain foods before exercising.

Management of Food Allergies

  • Avoidance: Once diagnosed, strict avoidance of the allergenic food is necessary.
  • Emergency Plan: In cases of severe allergies, carrying an epinephrine auto-injector (EpiPen) is recommended for use in case of accidental exposure.
  • Desensitisation Therapy: In some cases, oral immunotherapy (OIT) may be used to gradually increase tolerance to the allergen under medical supervision.

A food allergy blood test provides valuable information in diagnosing food allergies and guiding the management plan. It’s essential to work closely with a healthcare provider, usually an allergist, to interpret results and create a personalized care strategy.

Results – 2 days from Laboratory receiving sample

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