What is an Allergy Blood Test? An allergy blood test measures a substance called immunoglobulin E (IgE) in your blood. IgE is an antibody that your body makes. If you have allergies, you may have more IgE in your blood than normal. Allergies are a common, long-term condition that involves your immune system. Your immune system makes antibodies to fight off viruses, bacteria, and other things that can make you sick. With allergies, your immune system treats one or more harmless substances, such as pollen or peanuts, as a threat. To fight the "threat," your immune system makes IgE antibodies. This is what causes your allergy symptoms.

Harmless substances that may cause allergies are called allergens. Common allergens include:

Pollen

Dust

Mold

Animal dander

Certain foods, including nuts and shellfish

Certain medicines, such as penicillin.

Allergy symptoms depend on the type of allergy you have. They can range from itching and sneezing to asthma or a life-threatening condition called anaphylactic shock. Other names: IgE allergy test, Quantitative IgE, Immunoglobulin E, Total IgE, Specific IgE, RAST, CAP, ELISA