Glossary

Allergen Allergens are antigenic proteins which cause allergy
Allergic Sensitisation Occurs when an individual who produces IgE to a particular allergen (atopic) does not have a clinical allergic reaction when exposed to it. This is why using specific IgE as an allergy screen is inappropriate as many people are sensitised to an allergen rather than allergic to it.
Allergy An abnormal immune reaction to a substance which is
not in itself harmful. It can be described as immediate or delayed. Immediate allergy is usually, but not exclusively, mediated by IgE and is also known as type 1 hypersensitivity
Anaphylaxis A serious allergic reaction that involves more than one organ system (for example, skin and respiratory tract and/or gastrointestinal tract), can begin very rapidly, and can cause death.
Angioedema Angioedema is characterized by:

  1. A sudden, pronounced swelling of the lower dermis and sub cutis
  2. Sometimes pain rather than itching
  3. Frequent involvement below mucous membranes
  4. Resolution that is slower than for wheals and can take up to 72 h
Asthma Asthma is a chronic inflammatory disorder of the airways in which many cells play a role, in particular mast cells, eosinophils and T lymphocytes, causes recurrent episodes of wheezing, breathlessness, chest tightness, and cough particularly at night and/or in the early morning. These symptoms are usually associated with widespread but variable airflow limitation that is at least partly reversible either spontaneously or with treatment.
Atopy Atopy is a personal and/or familial tendency, usually in childhood or adolescence, to become sensitized and produce IgE antibodies in response to ordinary exposure to allergens, usually proteins. The production of specific IgE in response to exposure to common environmental allergens such as pollens, animal dander or food. Atopy can also be defined as the presence of certain conditions such as eczema, asthma, hay fever or food allergy.
Eczema The umbrella term for a local inflammation of the skin should be dermatitis. What is generally known as “atopic eczema/dermatitis” is not one, single disease but rather an aggregation of several diseases with certain characteristics in common. A more appropriate term is eczema. The subgroup related to allergic asthma and rhinoconjunctivitis, i.e. eczema in a person of the atopic constitution, should be called atopic eczema. Close contact with low molecular–weight chemicals may provoke a predominantly TH1 lymphocyte mediated allergic contact dermatitis. The non-allergic variety can also be described by terms like irritant/toxic
contact dermatitis.
Food allergy An immune-mediated hypersensitivity reaction to food divided into IgE (immediate onset) and non IgE mediated (delayed onset) reactions.
Intolerance A reaction to certain food ingredients or food additives.
RAST This term no longer used. It refers to obsolete technology. The correct term is serum specific IgE testing.
Rhinitis Inflammation of the nasal mucosa may be allergic or non-allergic. Referred to rhinoconjunctivitis when also involving conjunctiva. Characterised by 4 cardinal clinical features: Nasal discharge, blockage itch and sneezing.
Urticaria Urticaria is characterized by the sudden appearance of wheals and/or angioedema. A wheal consists of three typical features:
1. A central swelling of variable size, almost invariably surrounded by a reflex erythema
2. Associated itching or, sometimes, burning sensation
3. A fleeting nature, with the skin returning to its normal appearance usually within 1–24 h