http://repub.eur.nl/res/aut/20666/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/17177/ 1998-10-23T00:00:00Z l.l.l DEFINITION In 1873, Blackley was the first to establish that pollen played a role in the causation of hay fever or "slmuller catarrh"(l). Von Pirquet introduced in 1906 the tern] allergy (2). He discovered that under certain conditions, patients, instead of developing immunity, demonstrated an increased reaction to repeated exposure with foreign substances. Nowadays, allergy has been defined as Ituntoward physiologic events mediated by a variety of different immunologic reactions" (3). TIlls definition implies the acceptance of three criteria necessary for the definite diagnosis of an allergic state: (I) identification of the allergen, (2) establislullent of a causal rclationship between exposure to the antigen and occurrence of the disease, and (3) demonstration of an inununologic mechanism involved in the illness. Allergy is sometimes confused with atopy and the two are sometimes used as synonyms. Atopy refers to a hereditary predisposition to produce the antibody immunoglobulin E (IgE). TIle most important atopic diseases are atopic dennatitis, allergic rhinitis and allergic asthma. 1.1.2 TYPES OF RHINITIS Allergic rhinitis is an IgE-mediated disease, in which symptoms are the result of aeroallergen exposure. The patient may complain of seasonal or perennial symptoms, although the latter may show seasonal exacerbations.