Predictors of group 5 grass-pollen allergens in settled house dust: comparison between pollination and nonpollination seasons.

BACKGROUND: Some sensitive pollen-allergic patients may experience perennial symptoms, and for these patients it is vitally important to know the concentration of grass-pollen allergens in their homes. The main objective of this study was to detect predictors associated with high grass allergen concentration in settled house dust during and outside the grass pollination season.
METHODS: We detected group 5 grass-pollen allergens in dust samples from randomly selected homes of three counties in the region of Sachsen-Anhalt: Hettstedt (n=183), Zerbst (n=152), and Bitterfeld (n=119). Dust samples were collected from the floors of living rooms (LR) and children's rooms (CR) from April 1996 to March 1998.
RESULTS: Phl p 5 was detected in settled house dust in 91% of the homes. The range was between undetectable (<30 ng/m2) and 4300 ng Phl p 5/m2 sampling area during grass pollination, and 1300 ng Phl p 5/m2 outside the pollination season, respectively. We observed a partially higher concentration of indoor allergenic activity several weeks after the grass-pollen peak. A positive association was found between Phl p 5 levels and total dust amounts throughout the year. Thus, we assume that grass allergens accumulate in settled house dust. During pollination, the Phl p 5 levels are 1.8 times higher in homes where vacuuming of carpets takes place only once a week or less than in those vacuumed daily. Furthermore, higher concentrations of Phl p 5 in settled floor dust can be expected in homes located within suburban areas (mean ratio [MR] 1.74) and prefabricated slab buildings (MR=1.54).
CONCLUSIONS: Quite high levels of Phl p 5 accumulate in settled house dust even during periods when no grass pollen is present in the atmosphere. The removal of dust by frequent cleaning reduces the indoor exposure to grass allergens. Such information is essential to train patients in allergen avoidance.