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Total IgE

What is total IgE?

Total IgE measures blood levels of antibodies produced by your immune system in response to allergens.

Immunoglobulin E (IgE) is an antibody that initiates an allergic reaction. When you are exposed to an allergen—a normally non-harmful substance that the immune system assumes is dangerous, like peanuts—your body makes specific IgE antibodies designed to recognize that allergen in the future. Then, when you are re-exposed to the same allergen, your immune system quickly produces a large amount of allergen-specific IgE particles to identify and eliminate the allergen. 


What does total IgE test for?

The total IgE test detects the presence of IgE antibodies in your blood, indicating an increased likelihood that you will experience allergic reactions. Tests for allergen-specific IgE particles are then used to provide information about the specific substances causing your allergic reactions.


How do I know if I am allergic to something?

Allergic reactions can range from localized patches of red, itchy skin to anaphylaxis, which involves a sudden drop in blood pressure and difficulty breathing. Allergic reactions can vary widely in both type and severity depending on the person and allergy. The following symptoms are strong indications that you should measure your IgE levels:

  • Itchy or watery eyes
  • Sneezing and/or coughing
  • Periodic or persistent itching, hives
  • Congestion
  • Persistent diarrhea
  • Difficulty breathing
  • Nausea or vomiting


What is the difference between IgG and IgE?

Unlike an IgG test  (known as a food sensitivity test), which only measures the common antibody immunoglobulin G and doesn't accurately predict specific food allergies, an IgE test focuses on the class of antibody that's directly associated with allergic reactions — giving you much more specific results when it comes to identifying allergic triggers.


What  is a normal IgE level?

Your IgE test results are reported in fluorescent standard units (FSU). A reading lower than 0.01 FSU indicates no detectable IgE. Generally, the higher the level of IgE, the greater the risk that you will experience allergic symptoms. Each potential allergen is in a class based on this level, as below.

Class 0/1

0.01–0.34 FSU

Clinical relevance undetermined

Class 1

0.35–0.70

Low sensitivity

Class 2

0.71–3.50

Moderate sensitivity

Class 3

3.51–17.50

High sensitivity

Class 4 and above

17.51–50.00

Very high sensitivity

Class 5

50.01–100.00

Very high sensitivity

Class 6

>100.00

Very high sensitivity


What does a high level of IgE mean?

While the higher the IgE level, the greater the likelihood you will have allergic symptoms for a particular allergen, even allergens that fall into the lower Classes should be monitored. They can contribute to the cumulative allergen burden, for example during allergy season. 


What can I do about elevated IgE levels?

If you have elevated IgE levels for any indoor, outdoor, or food allergies, a board-certified allergist can work with you to create a program that helps to alleviate symptoms. This can include the use of antihistamine and other medications, allergen avoidance and immunotherapy.

References

Last updated:
September 23, 2021

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