Grass pollen counts, air pollution levels and allergic rhinitis severity.

Background: Little is known about the relation between allergic rhinitis severity and airborne pollen in combination with air pollutants.

Objective: To model the risk of suffering from severe seasonal allergic rhinitis (SAR) as a function of both pollen count and air pollution levels in a large nationwide sample of patients whose SAR was diagnosed by a physician and confirmed by skin prick test positivity or specific immunolglobulin E to common aeroallergens.

Methods: The severity of SAR symptoms was estimated with the Symptomatic Global Score (SGS) among 36,397 patients suffering from an untreated and uncomplicated SAR between May and August 2004 in metropolitan France.