Blood Allergy Test

RAST Test, IgE Immunocap

A Test to Help Determine Allergies

A blood test for allergy is another one of the tests used to help determine if your child is allergic to eggs.

A blood test for allergies is often called, IgE Immunocap. IgE stands for immunoglobulin E, which is the antibody that triggers food allergy symptoms. An older test called the RAST test may also be used based on your doctors perference.

What happens during a blood test?

A blood test for allergies is similar to any other blood draw test.
You'll take your perscription to the lab and have some blood drawn.

In a blood test for allergies you are looking to discover if this antibody to the egg protein is present. A blood test for allergies does not predict the amplitude or severity of an allergic reaction but does help in discovering if an allergy could be present.

Blood allergy tests are not affected by antihistamines and they can be administered when a rash is present.

False Positives

Here’s the deal…
50-60% of all blood tests AND skin prick tests present false positives!
This is why you need multiple tests to confirm each other and the advice of an experienced allergist.

Consider this:

  • Results from a blood test show your child might indeed have antibodies to eggs but they might not manifest an allergic reaction.
  • The blood test may detect similar proteins as positive.

Remember, these are tests for your allergist to determine if it’s safe for your child to have an oral food challenge.
A 2018 study shows a correlation between anaphylaxis during an oral food challenge and increased specific Immunoglobulin levels.