Urban versus rural environment--any differences in aeroallergens sensitization in an allergic population of Cova da Beira, Portugal?

Cova da Beira is an interior central region of Portugal, with a population of 93000 inhabitants divided in urban and rural living areas. The aim of this study was to access the prevalence of aeroallergens sensitisation in an allergic population, according to the urban and the rural environmental exposure and according to age. 1096 patients observed for suspected allergic symptoms, for a five-year period (1995-2000) were submitted to skin prick tests and were included in this study. They were divided in two environmental exposure groups (A: urban; B: rural) and in to four age subgroups (subgroup I: < or = 10yr; subgroup II: 11-20yr; subgroup III: 21-40yr; subgroup IV: >40yr). The total population included 444 male (40.5%) and 652 female (59.4%) with an average age of 26.5 +/- 17.2 yr. 83% of the 1096 performed SPT were positive. The frequency of aeroallergens sensitisation, comparing the urban versus the rural environment, was respectively: D. pteronyssinus 32% and 34.7%, D. farinae 28.5% and 30.7%, moulds mixture 15.3% and 12%, cat dander 17.1% and 15.2%, dog dander 11% and 10%, grasses mixture 51.3% and 36.4%, Parietaria judaica 29.4% and 14%, Olea europea 30.2% and 23.3%. The sensitisation to indoor aeroallergens, was similar in all the age subgroups and it was lower than that to pollens. There were important differences concerning the pollen sensitisation, when comparing the urban and the rural environmental exposure. We admit that pollution could enhance the sensitisation to pollens in the urban environment.