The role of inhalant allergens in allergic airways disease.

Immunoglobulin (Ig) E-mediated sensitization to domestic inhalant allergens (eg, dust mite, cockroach, cat, and dog) is the most important risk factor for asthma. The severity of asthma increases among atopic patients exposed to high levels of sensitizing allergen. In addition, synergism between high allergen exposure and respiratory virus infection increases the risk of asthma exacerbation. However, opinions on the role of allergen avoidance in the management of asthma are diverse, partly because most currently used allergen avoidance measures are usually tested in highly artificial experimental conditions, often with no assessment of their effect on personal inhaled allergen exposure or their clinical effectiveness. While there is little evidence for the clinical benefits of single avoidance measures (eg, bedding encasings, vacuum cleaners, and air filters), multifaceted intervention in carefully selected patients may be of benefit. Until conclusive evidence is available, a pragmatic approach in clinical practice should involve the following: (a) interventions tailored to the patient's sensitization and allergen exposure (if exposure cannot be estimated, specific IgE antibody level or the results of skin testing can be used as a marker); (b) a multifaceted allergen avoidance regime, based on removal of the accumulating allergen; (c) initiation of the intervention as early as possible. Currently, no evidence-based advice on the use of allergen avoidance for prevention of allergic disease can be given; however, it is increasingly clear that no single strategy will be applicable to all children, only to those with specific genetic susceptibility.