Difference in symptom severity between early and late grass pollen season in patients with seasonal allergic rhinitis

The aim of this study was to delineate this relationship between seasonal allergic rhinitis symptoms and grass pollen concentrations in the Netherlands.Grass pollen allergic patients (n = 80 [2007] - 84 [2008]) were enrolled into the study. They were asked to enter their seasonal allergic rhinitis symptoms (runny nose, sneezing, blocked nose, post nasal drip, and eye symptoms) daily on a scale from 0 to 3 to the study centre either by short message service (SMS) or by internet from May-July 2007 and April-July 2008. Daily pollen counts were used to define the early and the late grass pollen season as the period 'before and during' respectively 'after' the first grass pollen peak (more than 150 pollen/m3).At similar grass pollen concentrations, the daily mean of the individual maximum symptom scores reported in the early season were higher as compared to that reported in the late season [differences of -0.41 (2007) and -0.30 (2008)]. This difference could not be explained by medication use by the patients nor by co-sensitization to birch.We conclude that seasonal allergic rhinitis symptoms at similar grass pollen concentrations are more severe in the early flowering season as compared to those in the late flowering season. This finding is not only relevant for development of forecasts for seasonal allergic rhinitis symptoms but also for understanding symptom development and planning and analysis of clinical studies.Allergic rhinitis is amongst the most common chronic diseases of the world. It results from IgE-mediated inflammation after allergen exposure of the nasal mucosa and includes symptoms such as rhinorrhea, nasal obstruction, nasal itching and sneezing [1]. The majority of these patients (70-80%) also report ocular symptoms [2].Grass pollen exposure is one of the major causes of allergic rhinitis in many parts of the world [3,4] The grass family comprises more than 10,000 wind pollinated species world wide. Since these species flower in succession, grass poll