Allergic rhinitis: A general term used to apply to anyone who has symptoms of nasal congestion, sneezing and a running nose due to allergies. This may or may not be a seasonal problem or caused by other allergens such as house dust, animal danders, and perhaps even some foods.

Allergist: A doctor specializing in the treatment of allergy.

Allergy: An overreaction of the immune system to an ordinarily harmless substance known as an allergen.

Alveoli: Tiny air sacs that make up lung tissue where the exchange of oxygen and carbon dioxide occurs.

Antihistamine: Medication taken to counteract the effects of histamine, which is produced by the body when exposed to an allergen.

Anti-inflammatory: A substance that reduces or inhibits swelling of inflammation.

Bronchial tubes: Tubes or airways that conduct air in and out of the lung; the site of the obstruction in asthma.

Bronchoconstrictor: A substance that causes the airways in the lungs to narrow.

Contact dermatitis: An allergic reaction affecting areas of the skin which become red, itchy and inflamed after contact with certain substances such as plants, cosmetics, medications, metals and chemicals. The most common cause of contact dermatitis is poison ivy.

Cortisone: Group of drugs or steroids derived from the adrenal gland used to control asthma and many other medical conditions.

Decongestant: Medication used to shrink swollen nasal membranes, promoting the free flow of air through the nose and sinuses. It is available as a topical nasal spray or drops, or in tablet, liquid, or capsule form.

Epinephrine: Adrenaline; used in emergency treatment of acute bronchospasm and anaphylaxis.

HEPA: High-efficiency particulate air purifier. HEPA filters can be used in room air purifiers, central ventilations systems, and vacuum cleaners.

Histamine: A substance released by the body in response to an allergen. This can lead to allergy symptoms.

Humidification: Addition of moisture to air. May be used to loosen dried secretion in sinuses or bronchial tubes.

Immune system: The body's defense system, composed of specialized cells, organs, and body fluids. It has the ability to locate, neutralize, metabolize, and eliminate unwanted or foreign substances.

Prednisone: Cortisone or steroid drug that doctors most commonly use to treat an asthma relapse.

Seasonal allergic rhinitis 'hay fever': Caused by allergy to pollens of trees, grasses, or weeds, or to mold spores. The name 'hay fever' is actually a misnomer since hay is not a common allergen and no fever occurs.

Sinus: Space within the skull that communicates with the air passages by way of throat or nose.

Sinusitis: Infection in the sinus.

Urticaria (hives): An outbreak of red, itchy welts of varying sizes on the skin. When the swellings are large and invade deeper tissues, they are called angioedema. They may develop on the face, lips, tongue, throat, eyes, ears, or even internally. Hives can be caused by allergic or non-allergic mechanisms. Allergies to foods are well-known causes.

Wheeze: A whistling or sighing sound caused by narrowing of the respiratory passage. Usually accompanied by difficult breathing; a common symptom of asthma.