An allergen-specific immunoglobulin E (IgE) blood test is done to check whether a person is allergic to a particular substance.
An allergic reaction occurs when the immune system overreacts to something, often in the environment, that’s harmless to most people. To protect the body from this perceived threat, or allergen, the immune system of an allergic person produces antibodies called immunoglobulin E.
IgE antibodies are found mostly in the lungs, skin, and mucous membranes. They cause mast cells (a type of cell involved in the body’s immune response) to release chemicals, including histamine, into the bloodstream. It’s these chemicals that bring on many of the allergy symptoms that affect a person’s eyes, nose, throat, lungs, skin, or gastrointestinal tract.
Because IgE antibodies are unique to each allergen (for example, IgE produced in response to pollen differs from IgE produced after a bee sting), checking for specific variants in the blood can help determine if an allergy is present.