Allergy and Immunology
Common Terms

Glossary of Allergic Terms and Diseases

Allergen: A substance, typically a protein, that elicits an IgE response associated with clinical symptoms

Allergic Reaction: An adverse immunological reaction associated with allergic responses

Allergies: The constellation of clinical problems typically associated with allergic conjunctivitis, allergic rhinitis, asthma and eczema

Allergy: A reaction of the immune system that is triggered by allergens, associated with IgE and is typically harmless to most people

Anaphylaxis: An acute IgE-mediated allergic response that can be life-threatening

Antibody(ies): A protein produced by the body’s immune system that helps neutralize germs by recognizing and binding a specific antigen

Antigen: A substance, typically a protein, that elicits an immune response (such as an antibody)

Asthma: Reversible airway obstruction associated with allergy, typically triggered by aeroallergen exposure

Atopic Dermatitis: Also known as eczema. Dry, itchy skin rash associated with allergies.

Atopy: The predisposition to develop the constellation of allergic diseases including eczema, rhinitis, asthma, and conjunctivitis in individuals with a family history of these problems. This inherited tendency to develop certain allergic hypersensitivity reactions is associated with elevation of IgE
Basophil: A circulating white blood cell that bears IgE receptors, releases histamine and is involve in allergic reactions

Corticosteroid Drugs: A drug of the corticosteroid classification that is typically used for its anti-inflammatory action

DBPC (Double-blind Placebo-controlled) Study: This is a research study in which both the patient and the healthcare provider are unaware of whether the subject is being given the active drug or a placebo (sugar pill) in order to avoid bias in interpretation of the results

Desensitization: Loss of immunological sensitization

Eosinophil(s): A white blood cell that contains granules that absorb the eosin stain

Food Allergies: Allergic reaction to a food substance

Food Challenge: Exposure to a food with the aim of determining whether it will elicit an immunological or clinical response

Gastroesophageal Reflux (GER): Retrograde flow of acidic gastric contents into the esophagus
Hay Fever: Seasonal allergic rhinitis caused by exposure to pollen

Histamine: A substance produced by allergic inflammatory cells (mast cells and basophils) that triggers acute allergic symptoms

Hives: A raised and red skin reaction caused by a local or systemic exposure to a substance that is typically triggered by local mast cell activation

House Dust Mite: An insect that lives in dust, typically thrives on human skin flakes and is a potent and common allergen

IgE: Antibody of the E class that is involved in the the development of allergies by triggering mast cells and basophils

IgG: The most common form of protective antibody

Immunotherapy: Manipulation of the immune system to harness a beneficial effect

Inflammation: Swelling of a particular tissue typically caused by the body’s immune response to injury

Interleukin: A hormone in the body that regulates the communication between leukocytes
Leukocytes: White blood cells

Lymphocyte: A leukocyte is characterized by its small nucleus and mononuclear appearance that has a central roll in the adaptive arm (memory response) of the immune system

Macrophage: A leukocyte that is characterized by its ability to engulf (ingest) foreign substances such as bacteria and able to activate lymphocytes

Mast Cells: Leukocytes that have high affinity IgE receptors and are involved in triggering allergies

Natural Killer Cell: A white blood cell involved in killing unwanted cells

Neutrophil: A white blood cell that participates in host defence against bacteria and also is involved in propagating acute inflammation

Patch Test: A skin test that measures delayed reactions to an allergen

Pruritus: Itching

Rhinitis: Nasal congestion

Rhinorrhea: Clear nasal discharge
SCID: Abbreviation for Severe Combined Immune Deficiency

Skin Prick Test: Application of allergens to the skin in order to determine the presence of sensitization to an allergen

T cell: A component of the cellular part of the immune system that is involved in memory responses to foreign substances

Tryptase: An enzyme produced by mast cells that is found in acute and chronic allergic reactions. Its levels in the blood can be used to determine the presence of anaphylaxis

Urticaria: A raised rash characterized by its itchiness

Venom: Toxin present in animals such as bees and snakes that can cause an allergic reaction

Wheal: A raised bump on the skin often measured by skin prick testing for determining the presence of allergic response to an injected substance

Xerosis: Dryness of the skin of the mucus membrane

Complete Glossary

The Division of Allergy and Immunology provides patients and families with a complete glossary of definitions for allergic terms and diseases. Download the glossary in portable document format (pdf).