Glossary Allergen The protein (antigen) that triggers an allergic reactionin an individual Allergic conjunctivitis Red, itchy and watery eyes caused by an allergic reaction in sensitised individuals Allergy An inappropriate immune response to a harmless agent. Individuals may be allergic to just one antigen or a variety Anaphylactic shock An extreme allergic reaction involving the massive release of histamines. The immediate symptoms are rash, swelling of lips, mouth and throat. Rapid pulse, dizziness and shallow breathing follows. Can be fatal without treatment Antibodies Specialised proteins produced by cells of the immune system in response to invasion by a potentially harmful agent. One antibody is specific to one antigen. Antibodies either neutralise the antigen or help present it to the body's killer cells Antigen A protein that is recognised by the body as foreign. An allergen is a specific antigen to which a person is allergic Antihistamines These are drugs that block the action of histamine at its receptor sites. Also referred to as histamine antagonists. The older (classical) antihistamines cross the blood-brain barrier and cause sedation. newer non-sedating antihistamines do not have this adverse side effect Atopic eczema A predisposition to allergic skin reactions, and other allergic illnesses such as hay fever and asthma. the reason is likely to be due to an elevated production of IgE Basophils Special cells of the immune system that circulate in the blood. Basophils release the chemical mediators of inflammation during an allergic response Conjunctiva The thin protective membrane that covers the eye ball and the inner surface of the eye lid Conjunctivitis Inflammation of the conjunctiva in response to infection, irritation or injury. The signs include itchy, bloodshot and watery eyes Corticosteroids Drugs used to mimic the effects of natural steroids released from the adrenal cortex. They may have many uses including anti-inflammatory agents Dander Flakes of dead skin and strands of hair or fur left behind by animals (most commonly household pets) Decongestants Drugs used to reduce congestion and blockage of the nose, which can result from a cold or allergy. Usually these drugs mimic the effects of the sympathetic nervous system to shrink the blood vessels supplying the nose. Eczema (Also referred to as dermatitis); an inflammatory skin condition causing itching and redness and occasionally weeping Emollient An agent that soothes and softens the skin Histamine A hormone that acts on histamine receptors around the body, including those implicated in itch, sneezing and nasal discharge Histamine receptors Specialised proteins embedded in cell membranes to which histamine binds IgE (immunoglobulin type E) A type of antibody that results in the sensitisation of mast cells to subsequent exposure to an allergen Immunotherapy A way of reducing an individual's sensitivity to the allergen by exposing them to increasing doses over a period of time Mast cells Special cells of the immune system that carry antibodies and release histamine when the matching antigen binds. Mast cells are abundant in 'exposed' tissues such as the respiratory tract Perennial allergic rhinitis The persistent symptoms of allergy to, most commonly, house dustmites and animal dander Pollen count A measure of the amount of pollen released into the air. Most sufferers react when the pollen count reached about 50 grains per cubic metre Rhinitis Inflammation of the nasal mucosa Rhinorrhea The production of watery nasal secretions Seasonal allergic rhinitis Another term for hay fever Skin-prick test A simple test to assess the potential allegen. A small amount of allergen is injected into the skin. if the individual is allergic a localised inflammatory response is evoked Sodium cromoglycate An agent used prophylactically to stabilise mast cells and prevent or reduce the symptoms of hay fever Urticaria ('nettle rash', 'hives') An allergic skin reaction, which involves the appearance of individual swellings on the skin (weals) that resolves within hours