Starship Paediatric Immunology and Allergy

Specific IgE Blood Tests (sometimes called RAST)

Specific IgE (sIgE) tests are a way of doing allergy tests by a blood test rather than a skin test. A variety of foods and environmental allergens can be tested for. These tests involve taking a teaspoon of blood and the results are generally available after about 7 days.  For these reasons skin tests are the preferred option in the allergy clinic, as results are immediately available. 

sIgE tests may be preferred in situations where skin tests cannot be done, such as with continuous antihistamine treatment or severe eczema.  sIgE tests are sometimes used to predict the likely time course of growing out of a food allergy.  Importantly neither sIgE tests nor skin tests can predict the severity of an allergic reaction.

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https://www.healthpoint.co.nz/public/allergy-and-immunology/starship-paediatric-immunology-and-allergy/