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Allergen: Something that provokes an allergic reaction.

Allergic rhinitis: Inflammation of the mucous membrane of the nose caused by an allergic reaction. Hayfever is a type of allergic rhinitis.

Allergy: An inappropriate and potentially damaging response by the body’s immune system to a substance, such as pollen or house dust mites, to which it has become hypersensitive.

Anaphylactic shock: A rapid and severe allergic reaction that can cause intense swelling of the airways. Urgent medical attention is required.

Antibodies: Proteins that combine with substances identified as not belonging to the body, such as bacteria and viruses, in order to destroy them.

Antihistamine: A drug that blocks the effect of histamine.

Corticosteroid: Any member of a group of chemicals sharing a characteristic molecular structure. These hormones are produced in the adrenal cortex or made synthetically.

Cromones: Cromones prevent the release of histamine from mast cells that follows an encounter with an allergen.

Decongestant: A medicine that relieves nasal congestion.

Dermatitis: See eczema.

Early phase: The early phase of the allergic response is the initial, rapid reaction that occurs within minutes of an encounter with an allergy trigger. It involves the explosive release of histamine and, in airborne allergy, results in symptoms such as sneezing, runny nose and itching of the nose and eyes.

Eczema: A skin condition where the skin becomes red and inflamed that is often the result of allergy. It is also called dermatitis. www.skinflare-up.com

Eosinophils: A type of white blood cell.

Fever: A raised body temperature.

Gland: An organ that secretes chemical substances that can be used in the body, for example hormones. Some glands produce substances that are discharged into the surrounding part of the body, for example, lacrimal glands produce tears.

Glaucoma: A disease marked by increased pressure within the eyeball. It causes gradual loss of sight and tunnel vision.

Hayfever: Common name for seasonal allergic rhinitis, particularly when caused by pollen. Despite its name, it does not cause a rise in temperature.

Histamine: A chemical substance released in the body that causes contraction of smooth muscle and dilation of capillaries, leading to inflammation.

Hives: The common name for the condition urticaria; round, red weals on the skin that itch, sometimes with swelling, usually the result of allergy.

Hypersensitive: Allergic.

Immune system: The cells and chemicals within the body that protect against potentially harmful substances such as viruses and bacteria.

Inflammation: A reaction by the body to an injury or infection that involves heat, redness, swelling and pain.

Late phase: In addition to the early inflammation produced by airborne allergy, some people, experience a slower allergic process that involves several cells and mediator chemicals. This continues and reawakens inflammation and produces symptoms of nasal congestion or blockage. Chemicals produced by the late phase of the allergic response also cause the emotional symptoms such as irritability, loss of concentration and sleep disturbance.

Leukocytes: White cells in the blood.

Leukotrienes: Leukotrienes are chemical mediators of allergy. They are released by several types of cells and can cause inflammation.

Lymphocytes: Lymphocytes are small white blood cells that play a large role in defending the body against disease. They are responsible for immune responses. The two main types are B cells that make antibodies that attack bacteria and toxins and T cells that attack body cells themselves when they have been taken over by viruses or have become cancerous.

MAOI: See Monoamine oxidase inhibitor.

Mast cells: A connective tissue cell that is frequently injured during allergic reactions, releasing strong chemicals such as histamine that are very irritating and cause itching and swelling.

Monoamine oxidase inhibitor(MAOI): A type of antidepressant drug. This class of medicines can interact with many other types of drugs. The product label or leaflet will detail these interactions.

Mediator: In relation to allergy, a mediator is a chemical substance that acts as a messenger to induce activity or reaction.

Nasal blockage: A more severe form of nasal congestion where it is not possible to breathe through one or both nasal passages.

Nasal polyp: A small benign growth protruding from the mucous membrane of the nose.

Perennial: Lasting throughout the year.

Pollen: Fine powdery substance, usually yellow, consisting of microscopic grains discharged from the male part of a flower.

Polyp: See nasal polyp.

Prickly heat: An itchy inflammation of the skin with a rash. More common in hot weather, it is sometimes associated with allergy.

Raised temperature: Body temperature above normal (higher than 37ºC).

Rebound nasal congestion: Congestion that occurs as a result of continued use of nasal decongestant, especially spray and drops. Also known as drug-induced rhinitis. Treatment begins with total avoidance of decongestant use for several months.

Rhinorrhoea: Runny nose.

Seasonal: Occurring during a certain period of the year.

Sinusitis: Literally, inflammation of the nasal sinuses. The term is usually applied when infection is present.

Temperature: See Raised temperature.

Trigger: The common term for an allergen - a substance that provokes an allergic response such as pollen or house dust mite droppings.

Vaccination: The process of making someone immune to a disease by exposing the person to a harmless version of the bacterium or virus that causes it. Often given by injection. Desensitising injections to reduce allergy are sometimes informally referred to as ‘vaccinating against an allergy’.

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