Purpose of the Study
To determine whether there was a dose response between exposure to dust mite, cockroach and cat and sensitization to these allergens in inner-city children.
Five hundred children participating in the National Cooperative Inner City Asthma Study.
Children were prick skin-tested with a Multi Test device. Samples of home dust were collected from the floor and furniture in the kitchen, bedroom and living room, and the levels of major allergens for dust mite (Der p 1, Der f 1), cockroach (Bla g 1) and cat (Fel d 1) were measured by an enzyme-linked immunosorbent assay (ELISA) method.
Levels of each allergen correlated significantly between rooms in individual homes. Mite and cat allergen levels were frequently below the detection limit of the assay. Cockroach allergen (Bla g 1) concentrations in the bedroom were related to the prevalence of positive skin test responses to cockroach extract among the children, with an odds ratio for sensitization of 1.45 (1.11–1.92). Positive skin test responses to cockroach allergen were seen in 15% of children whose bedroom allergen levels were below the level of detection, compared with a rate of 32% in bedrooms with Bla g 1 levels of 1.2 U/g and 40 to 44% among those in bedrooms with levels of 4 U/g or greater. The relationship between exposure and positive skin test responses was stronger among atopic children with a greater number of positive skin responses.
Despite widespread exposure to household allergens, the strongest relationship between exposure and sensitization was observed in the bedroom. The dose response between exposure to cockroach allergen and sensitization suggested that exposure to low doses, 2 U/g or less, was a risk factor and that the risk plateaus above 4 U/g. Atopy modified the relationship of exposure to sensitization.
It is important to understand the relationship between environmental allergen exposure and the risk of atopic individuals becoming sensitized to that allergen. This knowledge is essential for development of environmental strategies aimed at reducing the amount of allergen in the environment. This study showed that higher levels of exposure clearly increase the risk of sensitization to cockroach allergen. The study also showed that atopic children are at higher risk of becoming sensitized at low levels of exposure to allergen. The strongest relationship of sensitization to cockroach allergen is in the bedroom, although the highest Bla g 1 levels are found in the kitchen. This has important implications for the strategies of effective allergen control and indicates that allergen removal in the bedroom may be particularly important.