Allergen-Specific IgE Antibody Test

Other names: Allergy Test, RAST Test.

The blood allergy test, or otherwise recognised as the RAST test and the allergen-specific IgE antibody test, is used to check for allergies. The test assesses the level of allergen-specific immunoglobulin E (IgE) in the bloodstream. IgE is an antibody which makes up part of the body’s immune system; the antibody is stimulated if a person comes into contact with an allergen for the first time. Common allergens include grass, certain types of food including dairy foods and nuts and animal fur.

The body automatically generates antibodies to combat the allergen and the IgE antibody binds to specialised mast cells, which are located in the respiratory system, the basophils (in the bloodstream) and the digestive system (in the gastrointestinal tract). When the individual next comes into contact with the allergen, the immune system will recognise it and produce histamine to trigger an allergic response.

What is the test used for?

It tests for allergies and monitors the efficacy of treatments or therapies. Doctors may advise patients to have the test if they experience symptoms of an allergy, including hives, irritated skin, itchy, red eyes, asthma or abdominal pain.

How is the test performed?

The test is performed by collecting and analysing a sample of blood, which is taken from a vein in the arm. A needle is inserted into a vein in the arm and a sample of blood is collected in a syringe. Once the sample has been taken, it will be bottled and labelled with the patient’s name; it will then be sent away to a laboratory for analysis.

What do the results show?

Positive tests usually indicate that an individual has an allergy; the levels of IgE do not reflect the severity of an allergic reaction so even if an individual has a positive result, they may not experience physiological symptoms of an allergy.

Specific Blood Tests

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