An allergy is an abnormal reaction of the immune system to substances which are usually harmless.
Allergies are caused by an inappropriate response of the immune system to a foreign substance known as an “allergen” (pollen, house dust mites, foods, etc.). Allergies can affect the skin, eyes, digestive system and certain parts of the airways, such as the nose or bronchial tubes. An allergy consists of acute visible symptoms combined with an underlying inflammation.
Researchers think that people inherit a tendency to develop allergies from one or both parents. Once the allergic trait has been inherited, specific allergies develop with time and exposure. Changes in the environment and lifestyles, the development of hygiene practices and the reduction of bacterial and viral infections, urbanisation, pollution and changes in dietary habits are all factors which seem to have contributed to the rapid increase in allergies.
Its occurrence is said to have doubled during the past 20 years. It is estimated that 20 to 30% of the developed world’s population suffers from allergies.
Each allergic individual reacts on average to 2 or 3 different allergens. Today, there are more than one hundred identified allergens grouped into main families: pneumallergens or respiratory allergens (house dust mites, pollen and plant-derived allergens, dander – cat hair, dog hair, etc. – mould and yeast), hymenoptera venom, food allergens, chemical or medicinal allergens and contact allergens. Allergies are a chronic and progressive condition which may worsen over time. If patients leave allergies untreated or inadequately treated, symptoms may get worse, or it may increase the risk of developing asthma or allergies to new substances causing the symptoms.
1. Bauchau V, Durham SR. Prevalence and rate of diagnosis of allergic rhinitis in Europe. Eur Respir J 2004;24(5):758-64.
2. Canonica GW et al. A survey of the burden of allergic rhinitis in Europe. Allergy 2007:62(S85):17-25.
3. Valovirta E, et al. The voice of the patients: allergic rhinitis is not a trivial disease. Curr Opin Allergy Clin Immunol 2008;8(1):1-9
- National Institute of Allergy and Infectious Disease. Airborne allergens. Something in the air. NIH Publication No. 03-7045. Available at: http://www.niaid.nih.gov/topics/allergicdiseases/documents/airborne_alle.... Accessed February 1, 2011.
- Bauchau V, Durham SR. Prevalence and rate of diagnosis of allergic rhinitis in Europe. Eur Respir J 2004;24(5):758-64.
- Canonica GW et al. A survey of the burden of allergic rhinitis in Europe. Allergy 2007:62(S85):17-25.
- Valovirta E, et al. The voice of the patients: allergic rhinitis is not a trivial disease. Curr Opin Allergy Clin Immunol 2008;8(1):1-9.