Effect of Allergen Concentrations on Symptoms of Asthma at 18 Months

Abstract

The objective of this study was to assess whether exposure to house dust mite allergens has an influence on respiratory symptoms and atopy at 18 months of age. A total of 616 women at risk of having a child who would develop asthma because of a family history were recruited from the antenatal clinics of six hospitals in Sydney, Australia. Families were randomized to a house dust mite avoidance group or a control group. Dust was collected from children's beds at regular intervals to measure house dust mite allergen (Der p 1) concentrations which were categorized into quintiles of exposure. At the age of 18 months, 529 children (85.9% of total sample) had an assessment of symptoms by a research nurse blinded to group status. Atopy by skin prick tests and serum IgE were also measured. Atopy to inhaled allergens (p = 0.79) or to Der p 1 was not associated with Der p 1 exposure (p = 0.87). "Doctor diagnosed asthma," "wheeze ever," and "wheeze in the absence of a cold" did not decrease with quintile of exposure. However, the highest quintile of exposure had a lowest prevalence of "wheeze for more than 1 week" (p = 0.012), "wheeze causing difficult breathing" (p = 0.012) and "emergency visit for wheeze" (p = 0.015) but with no significant trend across quintiles. The effectiveness of the intervention will not be known until the children are older and asthma can be more reliably characterized, however, these results have important implications for understanding how asthma and allergy develop.