Allergic rhinitis affects 15% to 20% of the general population with environmental allergens commonly implicated.<sup>55 Sibbald B., Strachan D.P. Epidemiology of rhinitis Asthma and Rhinitis Cambridge: Blackwell Scientific Publications (1995).  33

Haga clic aquí para ir a la sección de Referencias</sup> In 1880, Charles Blackley was the first person to implicate pollens in hay fever by performing skin tests and measuring pollen counts.<sup>11 Blackley C.H. Hay Fever: Its Causes, Treatment, and Effective Prevention  London: Balliere (1880). 

Haga clic aquí para ir a la sección de Referencias</sup> Since his pioneer work, many other allergens have been discovered and further insight has been gained into the role of allergens in rhinitis. Allergens are proteins or glycoproteins that are capable of eliciting IgE-mediated reactions. Although there are many potential allergenic proteins in the environment, few are clinically important, and even fewer have been isolated and characterized. A given allergen is considered major when there is IgE binding by radioimmunoelectrophoresis in 50% or more individuals sensitive to that allergen and minor if the IgE binding is present in less than 50% of allergic individuals.<sup>39 Løwenstein H. Quantitative immunoelectrophoretic methods as a tool for the analysis and isolation of allergens Prog Allergy 1978 ;  25 : 1

Haga clic aquí para ir a la sección de Referencias</sup> Most aeroallergens have molecular weights between 10 and 40 kD and are carried on particles (e.g., pollen grain and house dust) between 2 and 60 μm in size. The particle size largely determines the location of deposition of the allergen once it reaches the human respiratory tract. Studies have shown that particles of greater than 10 μm will generally only be deposited in the upper airways; those of 5 μm in size, will reach the lower airways 20% of the time, and those less than 2 μm in size will reach the lower airways 100% of the time.<sup>21 Corn M. Assessment and control of environmental exposure J Allergy Clin Immunol 1983 ;  72 : 231-241  [cross-ref]

Haga clic aquí para ir a la sección de Referencias, 76 Wilson A.F., Novey H.S., Berke R.A. , y al. Deposition of inhaled pollen and pollen extract in human airways N Engl J Med 1973 ;  288 : 1056  [cross-ref]

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It is convenient to divide the various allergens into those that exist in the outdoor environment, and those that exist in the indoor environment. In the outdoors, pollens of trees, grasses, weeds, and certain fungi (e.g., Alternaria and Cladosporium) represent the most common allergens that provoke rhinitis symptoms. Pollen-sensitive individuals typically experience seasonal rhinitis symptoms in predictable time intervals from one season to the next. Although fungi are more ubiquitous in nature and do not have distinct seasons like pollens, outdoor and indoor fungi thrive in a moist environment. Therefore, in temperate climates, fungi counts start to rise in spring with a peak in mid to late summer. Indoor allergens include fungi, animals, cockroaches, and dust mites. Unlike the outdoor allergens, which typically produce seasonal symptoms, indoor allergens often produce symptoms perennially; however, the symptoms are less drastic in nature, often making diagnosis more difficult.