The association of asthma and allergy has long been recognized. Recent studies confirm that sensitization among genetically susceptible populations to certain indoor allergens such as house-dust mite, animal dander, and cockroach or to the outdoor fungus Alternaria is a risk for developing asthma in children (Halonen et al. 1997; Sears et al. 1993; Sporik et al. 1990). Sensitization to outdoor pollens carries less risk for asthma (Sears et al. 1989), although exposure to grass (Reid et al. 1986) and ragweed (Creticos et al. 1996) pollen has been associated with seasonal asthma. It is widely accepted that the importance of inhalant sensitivity as a cause of asthma declines with advancing age (Pollart et al. 1989).

An allergic reaction in the airways, caused by natural exposure to allergens, has been shown to lead to an increase in inflammatory reaction, increased airway hyperresponsiveness (Boulet et al. 1983; Peroni et al. 1994; Piacentini et al. 1993), and increased eosinophils in bronchoalveolar lavage (Rak et al. 1991). Other research has demonstrated that asthma symptoms, pulmonary function, and need for medication in mite-sensitive asthma patients correlate with the level of house-dust mite exposure (Custovic et al. 1998; Huss et al. 2001; Sporik et al. 1990; Vervloet et al. 1991) and that reducing house-dust mite exposure reduces asthma symptoms, nonspecific bronchial hyperresponsiveness, and evidence of active inflammation (Morgan et al. 2004; Peroni et al. 2002; Piacentini et al. 1993; Simon et al. 1994). Inhalant allergen exposure to seasonal outdoor fungal spores (O'Hollaren et al. 1991; Targonski et al. 1995) and to indoor allergens (Call et al. 1994) has also been implicated in fatal exacerbations of asthma. These reports emphasize that allergen exposure must be considered in the treatment of asthma.

The important allergens for children and adults appear to be those that are inhaled. Food allergens are not a common precipitant of asthma symptoms. Foods are an important cause of anaphylaxis in adults and children (Golbert et al. 1969; Sampson et al. 1992), but significant lower respiratory tract symptoms are uncommon even with positive double-blind food challenges (James et al. 1994). However, asthma is a risk factor for fatal anaphylactic reactions to food or immunotherapy (Bernstein et al. 2004; Reid et al. 1993).

From: Section 3, Component 3: Control of Environmental Factors and Comorbid Conditions that affect asthma

Cover of Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma
Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma.
National Asthma Education and Prevention Program, Third Expert Panel on the Diagnosis and Management of Asthma.

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