IgE serum

Test name with synonym


RAST test; Radioallergosorbent test; Allergy screen; Allergen-specific IgE antibody test


Clinical definition of the IgE serum test

IgE testing is an essential tool in the diagnosis of allergy disorder. IgE is a protein associated with allergic reactions. It is normally found in very small amounts in the blood.  It is an antibody that functions as part of the body’s immune system. It is released by the immune system to fight against the foreign bodies and allergens that enter the body. IgE antibodies are generally found in the skin, lungs and mucus membranes of the body. They cause reactions as soon as they detect the presence of any environmental allergen such as pollen, fungus, spores or dander. The body perceives the potential allergen as a foreign substance and produces a specific IgE antibody that binds to specialized mast cells in the skin, respiratory system and gastrointestinal tract, and to basophils in the blood stream. During the next exposure the attached IgE antibodies recognize the allergen and cause the mast and basophil cells to release histamine and other chemicals resulting in allergic reaction. People with allergies often have elevated IgE levels.  IgE plays an important role in conditions such as asthma and various allergies, atopic dermatitis, certain types of cancer and is mostly associated with type 1 hypersensitivity. IgE levels are also elevated in children with parasitic infections.



Why is the IgE serum test done?


IgE serum test measures the amount of allergen- specific immunoglobulin E (IgE) in the blood inorder to detect an allergy to a particular substance. IgE is one of the five classes of antibodies. Antibodies are proteins made by the immune system that attack antigens, such as bacteria, virus, and allergens and neutralize the foreign objects that find entry into the body. IgE antibodies are found in the lungs, skin, and mucous membranes. They are associated mainly with allergic reactions (when the immune system overreacts to environmental antigens such as pollen or pet dander) and parasitic infection.  

What are the common signs/symptoms when the IgE serum test is done?




Nasal congestion

Tight throat

Trouble breathing



Red itchy eyes



Itching and tingling in the mouth

Abdominal pain

Vomiting and diarrhea

Symptoms may be seasonal (as with allergies due to pollen or molds) or year-round (as with food allergies).


What should I do before the IgE serum test?

Specimen type

Specimen collection procedure

Preparatory instructions before the test *

Serum (Blood Sample)

Venipuncture –

Collection of blood from a vein, usually from the arm.

No Fasting Required.

No other special preparations required.

*Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my IgE serum test results?


Reference Range*


0 to 100 IU/ml


0 to 100 IU/ml



10-15 years

Upto 200 IU/ml

Infants in first year of life

Upto 15 IU/ml

1-5 years

Upto 60 IU/ml

6-9 years

Upto 90 IU/ml



Inference: Elevated results usually indicate an allergy, but even if the specific IgE test is positive, a person may or may not ever have an actual physical allergic reaction when exposed to that substance. The amount of specific IgE present does not necessarily predict the potential severity of a reaction. A person's clinical history and additional medically supervised allergy tests may be necessary to confirm an allergy diagnosis.

‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’

Diseases/conditions related to the IgE serum test


Type 1 hypersensitivity.

Atopic dermatitis

Job syndrome

Hay Fever.


Other tests related to the IgE serum test

Total IgE

Complete blood count (CBC)

White blood cell differential count

Eosinophil count

Basophil count

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IgE (Immunoglobulin - E)