• pollens prevalence;
  • rural;
  • urban;
  • vertical increase

Background:  The effects of fluctuations in pollen counts have important implications for health services. Little research on the clinical implications of the vertical distribution of pollen in allergy symptoms has been carried out.

Methods:  We have investigated the allergic symptoms of a population of 17 171 patients coming from our health area (Valladolid, Spain) and living in the city and villages. We compared the prevalence of sensitization to different pollens: Graminae, trees and shrub in relation with the floor of the building where they were living.

Results:  Relative risk of pollen sensitization (confidence index, CI 95%) was higher in patients who were living at high floors than in those patients who were living in lower floors or at street level, independently of rural or urban conditions The chi-square showed a lineal trend in this relationship in the case of sensitization to grass pollen: χ2: 1794, P > 0.00001

Conclusions:  On the basis of our local investigations, natural pollen sensitization appears to increase with height where the patient lives. This paper reports clinical results on the influence of vertical pollen distribution in pollen allergy.