Blood Allergy Test

A blood allergy test is a method of allergy testing. A blood allergy test uses a needle to draw blood from the vein in your arm and then sent to a lab to be evaluated. The lab will measure your blood for the amount of trigger-allergen antibodies.

In an allergic reaction, the body’s immune system releases antibodies, such as Immunoglobulin E (IgE), to fight off the invading trigger allergen. These antibodies produced are specific to the trigger allergen.

Why would I need a blood allergy test?

It can take several weeks before getting blood allergy test results therefore skin allergy tests are the preferred method for allergy diagnosis. In some cases a blood allergy test may be recommended, such as:

  • If you are unable to temporarily stop medications, such as antihistamines and some antidepressants, for skin testing.
  • Cannot tolerate the required scratches or pricks for skin testing.
  • Have an unstable health condition.
  • Have asthma or a severe skin condition such as eczema or psoriasis.
  • History of a severe allergic reaction or anaphylactic reaction to an allergen.
  • There is a consistent negative result to skin allergy testing for a possible trigger allergen.
  • You are believed to have an allergy to inhaled (breathed through the nose) allergens.
  • To evaluate how well the immunotherapy, or allergy shots, are working.
  • To evaluate if you have outgrown the allergy. This may be especially beneficial in children with allergies.

What are the different types of blood allergy tests?

The blood allergy test can help identify allergies to: food, dust, pet dander, pollen, and molds. There are two types of blood allergy tests:

  • Enzyme-linked immunosorbent assay (ELISA). ELISA specifically measures the AMOUNT of allergy-specific antibodies in the blood. This blood allergy test is typically favored over a RAST test due to its efficacy and cost savings.
  • Radioallergosorbent test (RAST). RAST only IDENTIFIES not measures the allergy-specific antibodies in the blood.
  • Complete Blood Count (CBC). A CBC can provide the allergist with your white blood cell count which usually increases when exposed to a trigger allergen.

What happens if my blood allergy test shows I have an allergy?

Finding the trigger allergens antibodies in your blood would indicate a positive result and an allergy to the trigger allergen. Blood tests cannot measure the severity of a reaction therefor you can test positive for an allergen without ever having reaction. A negative result means you do not have a true allergy to the trigger-allergen, such as with people with oral allergy syndrome. In oral allergy syndrome, it is unlikely to test positive to foods due to it being a cross-reaction of pollen rather than a reaction to the food alone.

Is there any reason I can’t get a blood allergy test?

The only reasons to not get a blood allergy test are:

  • The costs of blood allergy tests are not always covered by health insurance.
  • It has an increased chance for false-positives and inaccurate results.
  • It isn’t effective in the diagnosis of food allergies or oral allergy syndrome.



Disclaimer: The information contained in this site is for educational purposes only, and should not be used as a substitute for a licensed physician. Please see your physician for diagnosis and treatment of any concerning symptoms or medical condition. Click here to read the full disclaimer.
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