Background: In allergic individuals, onset of symptoms is related to atmospheric pollen grain counts and aeroallergen concentrations. However, this relationship is not always clear.

Objectives: To analyze the correlation between grass pollen grain and aeroallergen concentrations in Ciudad Real, Spain, during the year 2004 and establish their association with symptoms in patients with allergic asthma, rhinitis, or both.

Methods: Two different samplers were used to assess allergen exposure: a Burkard spore trap to collect pollen grains and a high-volume air sampler to collect airborne particles. Individual filters were extracted daily in phosphate-buffered serum and analyzed by enzyme-linked immunosorbent assay based on serum containing high titers of specific immunoglobulin (Ig) E to grasses. The study population comprised
27 grass-allergic patients whose symptoms and medication were recorded daily.
Results: Grass pollens were detected between April 28 and July 18. There was a positive correlation between pollen grain counts and symptoms (r=0.62; P>.001). Grass aeroallergens were detected not only during the grass pollination period, but also before and after this period. There was also a very significant correlation between aeroallergen levels and symptoms (r=0.76; P<.0001). The threshold level for grass pollen was 35 grains/m3.

Conclusions: Grass-related allergenic activity is present throughout the year, demonstrating the existence of aeroallergens outside the pollen season. Symptoms in allergic patients may be related to airborne particle concentrations. This fact should be taken into account in the clinical follow-up and management of allergic patients.

Key words: Aeroallergen. Allergen quantification. Asthma. Grass. Grass threshold. Pollen count. Rhinitis.