Risk levels for mite allergens. Are they meaningful?

Allergens found in house dust are among the most common environmental antigens to which man is naturally exposed.Standardized methods for measuring allergen exposure are essential forassessing the relationship between exposure, sensitization, and theseverity of asthma. Monoclonal antibody-based assays are the most widelyused method for assessing allergen exposure. In the effort to define thebest "index of exposure" to mite allergens, several factors need to beinvestigated, including: 1) whether allergen should be measured inreservoir dust or airborne 2) whether the results of reservoir measurementshould be expressed as recovered allergen per unit weight or per unitarea. As yet, airborne sampling is insufficiently sensitive to producereliable and repeatable results. Therefore, measurement of house-dust-miteallergen concentration in reservoir dust should be regarded as thebest-validated index of exposure. The results should be expressed andreported both per unit weight (concentration) and per unit area. Thestrongest predictor of chronic symptoms and acute exacerbation of asthmais sensitization to indoor allergens. A simple dose-response relationshipbetween IgE-mediated hypersensitivity and allergen exposure has beenestablished. For example, exposure to more than 2 microg Group 1 miteallergen/g dust should be regarded as a risk factor for the development ofIgE antibody and asthma in susceptible children. The quantitativerelationship between exposure and symptoms in patients already sensitizedis complex due to a number of possible confounding factors (e.g., otherallergens, viruses, asthma medication). A simple threshold level forprovocation of asthmatic symptoms has not been clearlydefined.