House dust mite allergen exposure in infancy

Background Infancy may be a critical time for exposure to house dust mite a llergens, when exposure to high levels can increase the risk of allergic se nsitization and the development of asthma in later life. Objective To measure house dust mite allergen (Der p 1) concentration in th e infants' environment and examine lifestyle factors which may influence mi te allergen exposure. Methods Infants aged between 4 and 12 months (n = 134) from the western reg ion of Sydney, Australia, participated. Reservoir dust samples were collect ed from four sites within each home: infant's bed, second bed (adult or sec ond child's bed), lounge floor and sheepskins (where available). Settling a eroallergen was collected for 10-14 d in Petri dishes in the infant's room. Der p 1 was measured by ELISA. A questionnaire on types of bedding, sleepi ng and playing patterns of the infant was completed by the parents at the t ime of dust collection. Results All infants were exposed to at least one site with Der p 1 concentr ations greater than 10 mu g/g fine dust. The mean settling aeroallergen lev el in the infants' room was 24 ng Der p 1/m(2)day and this was weakly relat ed to bed allergen levels (r = 0.21, P<0.05). Mattress type had a weak effe ct on Der p 1 levels as measured in the whole bed (P = 0.07), while bed cov er and bed type had no effect (P > 0.6). The mean product of time spent at a site and its allergen concentration was highest for beds in 69% of infant s. Conclusion The high level of allergen exposure in the environment of this g roup of infants places them at an increased risk of early sensitization and development of asthma. Any strategy to reduce asthma prevalence should add ress these high and avoidable levels.