| characteristics of pollinosis caused by betula in patients from ourense (galicia, spain). | a retrospective study was performed to describe the features of the pollinosis caused by betula in the area of ourense, spain. the pollen count was carried out with a lanzoni volumetric hirts spore trap (1993-2000). the betula pollen represented 5% over the annual total (annual mean quantity: 965 grains). it was present in the air from march to mid-may. the highest peaks took place in april (maximum values mean: 131 grains/m3). the medical records of 222 patients (mean age 25.66 years) diagnosed ... | 2003 | 12968397 |