An allergy is a disorder in which the body becomes overly sensitive to a particular substance, known as an allergen. A specific reaction is then provoked whenever the allergen is inhaled, ingested or otherwise comes into contact with the person affected. The allergic reaction stimulates immune cells to release chemicals into the body. These chemicals cause a sudden inflammation of the affected area, which causes several unpleasant side effects. Allergens are diverse and affect different tissues and organs. Common types of allergies include allergic rhinitis (for example hayfever) and urticaria (hives).
Allergic rhinitis is a condition caused by an immediate hypersensitivity reaction in the nose. Although the symptoms resemble those of the common cold, unlike colds, they are not caused by a viral infection. It is characterised by episodes of nasal congestion, sneezing and watery nasal discharge. Other symptoms may include red, itchy, watery eyes, a sore throat, dry cough, headaches and facial pain, fatigue and dark circles under the eyes. Allergic rhinitis may be seasonal or perennial (year round). The condition affects around 1 in 4 people in Australia and New Zealand and can have an impact on quality of life, including fatigue, learning ability and work performance. The development of an allergy, (such as allergic rhinitis), begins with the first exposure to an allergen, which leads to the production of antibodies. These antibodies then become attached to immune cells throughout the body, stimulating them to release inflammatory chemicals after subsequent exposure to the allergen in question.
Seasonal (Intermittent) Allergic Rhinitis
Seasonal allergic rhinitis, or hayfever, is caused by an allergy to pollens from grasses, flowers, weeds or trees. This form of rhinitis causes sudden, frequent attacks of sneezing, nasal discharge and congestion. These episodes may also be accompanied by eye symptoms, such as stinging, watering eyes and conjunctivitis. The timing of hayfever attacks differ from person to person, depending on the plant involved and its pollination time. Trees pollinate in late winter and early spring, with grasses flowering next. In Australia, pollen numbers are lower on the east coast, as the prevailing winds come from the sea and protection is given from westerly winds by the Great Dividing Range. The Victorian south coast experiences higher pollen numbers due to prevailing winds from the north, which carry pollen from northerly grasslands.
Perennial (Persistent) Allergic Rhinitis
Perennial allergic rhinitis is a hypersensitivity reaction to allergens in house dust, animal dander or fungal spores. Symptoms are similar to those of seasonal allergic rhinitis but occur on a more continual basis and are usually less severe.
The severity of allergic rhinitis is defined as mild or moderate/severe. Mild allergic rhinitis does not interfere with sleep, school, work activities or general daily activities and only causes minor discomfort. In moderate or severe cases, there can be impairment of sleep, work or school productivity and the ability to take part in sport/ leisure activities.
Urticaria, also known as hives, is an itchy rash caused by the release of the chemical histamine during an allergic reaction. The rash may consist of individual swellings, called welts or wheals, which may appear rapidly and then disappear within hours. When the wheals involve the lips, eyes or tongue, it is essential that you seek medical advice, as swelling may become severe and constitute a medical emergency due to breathing difficulties. It is estimated that around one in six people will experience at least one attack of urticaria in their lives. In approximately one third of cases, the cause is not known.