What is a radioallergosorbent (RAST) blood test?

A RAST (radioallergosorbent) blood test looks for specific immunoglobulin E (IgE) antibodies in your blood. If the antibodies are present, it most likely indicates a true allergic reaction. RAST is the safest type of allergy test, but compared with a skin prick test, it takes longer to produce results and it can't test for as many allergens at once.

This type of allergy test is typically used only in special circumstances where skin testing is not advised -- for example, if a person has a severe skin condition or is taking certain medications.

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