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Definition

IgE Antibodies are a type of immunoglobulin made by the body which are implicated in allergic reactions.

Description

The immune system produces at least five kinds of immunoglobulins (Ig) or antibodies (IgA, IgD, IgE, IgG and IgM), but the principal one that participates in allergic reactions is immunoglobulin E, or IgE. Every individual has different IgE antibodies, and each allergic substance stimulates production of its own specific IgE. An IgE antibody made to respond to ragweed pollen, for example, will react only against ragweed, and not oak tree or bluegrass or any other kind of pollen. When the antibodies encounter the allergen they are programmed against, they immediately signal the basophils or mast cells to unleash histamine or other mediating chemicals into the surrounding tissue. It is these chemicals - mainly histamine - that cause the familiar allergic reactions. Histamine released in the nose, eyes, and sinuses, for example, stimulates sneezing, a runny nose, and itchy eyes. Released in the lungs it causes narrowing and swelling of the lining of the airways and the secretion of thick mucus. Released in the skin, it causes rashes and hives. And in the digestive system, it causes stomach cramps and diarrhea.

Diagnosis

Quantitative determination of total serum IgE can be made rapidly and accurately by nephelometry, a technique that measures light scattered from a beam passed through a solution. Specific IgE levels must be measured with more sensitive techniques such as by radioallergosorbent testing (RAST) or allergy skin testing. A large number of substances have been found to have allergic potential. They are known as allergens. Measurable allergen-specific antibodies can be identified by radioallergosorbent tests (RAST). It is recommended that a patient's serum be first screened with a selected panel of six allergens and then followed, if appropriate, by an extended panel of additional allergens. The purpose of study is to test for reaction to certain respiratory and food allergy stimulants. The RAST tests measure the increase and quantity of allergen-specific IgE antibodies. These measurements are used in persons, especially children, with extrinsic asthma, hay fever, and atopic dermatitis (eczema) and are an accurate and convenient alternative to skin testing. Although more expensive, they do not cause hypersensitivity reactions.

Questions

What is the purpose of RAST? Is it intended to complement skin testing? What does the test measure? Will it pinpoint the cause of the allergic reactions? Are further tests required?