Allergy immunotherapy: Stimulation of the immune system with gradually increasing doses of the substances to which a person is allergic.  Immunotherapy can modify or stop the allergy by reducing the strength of the IgE response.  It is very effective for patients that can demonstrate allergies to pollen, mites, animal dander, and stinging insects. I can takes six months to a year to become effective, and injections are usually required for several years.

Anaphylaxis: Allergic reaction.  In severe cases, this can include potentially deadly anaphylactic shock.

Autoimmune: Pertaining to autoimmunity, a misdirected immune response that occurs when the immune system goes awry and attacks the body itself. Almost everyone has a decrease of autoimmunity.  However, when this autoimmunity becomes pathogenic it known as autoimmune disease.  This progression is determined by genetic influences as well as environmental triggers.

B cell: A type of white blood cell and, specifically, a type of lymphocyte. Many B cells mature into what are called plasma cells that produce antibodies (proteins) necessary to fight off infections while other B cells mature into memory B cells.  All of the plasma cells descended from a single B cell produce the same antibody which is directed against the antigen that stimulated it to mature. The same principle holds with memory B cells. Thus, all of the plasma cells and memory cells "remember" the stimulus that led to their formation. The maturation of B cells takes place in birds in an organ called the bursa of Fabricus. B cells in mammals mature largely in the bone marrow.  The B cell, or B lymphocyte, is thus an immunologically important cell.

Edema: The swelling of soft tissues as a result of excess water accumulation.

Histamine: Substance that plays a major role in many allergic reactions.  Histamine dilates blood vessels and makes the vessel walls abnormally permeable.  It is responsible for many of symptoms of allergy and asthma.

Immunoglobulin: A protein produced by plasma cells and lymphocytes and characteristic of these types of cells.  Immunoglobulins play an essential role in the body's immune system.  They attach to foreign substances, such as bacteria, and assist in destroying them.  The classes of immunoglobulins are termed immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), immunoglobulin D (IgD) and immunoglobulin E (IgE).

Immunoglobulin E: Abbreviated IgE. A class of immunoglobulins that includes the antibodies elicited by an allergic substance (allergen). A person who has an allergy usually has elevated blood levels of IgE. IgE antibodies attack and engage the invading army of allergens.

Mast cell: A connective tissue (such as skin and airway tissue) cell whose normal function is unknown but which is frequently injured in allergic reactions, releasing chemicals including histamine that are very irritating and cause itching, swelling, and fluid leakage from cells. These allergic chemicals may also cause muscle spasm and lead to lung and throat tightening, as in asthma.

T cell: A type of white blood cell that is of key importance to the immune system and is at the core of adaptive immunity, the system that tailors the body's immune response to specific pathogens.  The T cells are like soldiers who search out and destroy the targeted invaders. There are several different types of mature T cells.  Not all of their functions are known. T cells can produce substances called cytokines such as the interleukins which further stimulate the immune response.

Urticaria: Raised, itchy areas of skin often mediated by mast cells and histamine.  Hives can be rounded or flat-topped but are always elevated above the surrounding skin.   The hives are usually well circumscribed but may be coalescent and will blanch with pressure.  The hives typically last less than 4 hours but they may stay longer.