Risk factors for rhinitis in schoolchildren

RATIONALE:The intranasal dynamics of pollen particles (PP) is not fully understood although important for study of mechanisms of pollinosis.We demonstrated changes in the number of PP in various steps from inhalation to allergic reaction.METHODS: Head-high airborne Japanese cedar pollens (JCP) were collected using a portable sampler at 5 L/min of force.Intranasal PP was washed out with 200 mL saline and counted in lavage.Experimental PP inhalation was conducted through a pollen chamber.PP in expiration was counted in expired air in a bag alter PP inhalation.Cry j 1, a major allergen of JCP, were determined in supernatants after incubation of JCP with buffered saline by enzyme-linked immunosorbent assay.RESULTS: Airborne JCP was 183.0 _ 43.1/h (n=23) in the center of Tokyo.Ninety-nine percent of PP inhaled experimentally was deposited in the nose (n=3), and 80% of PP deposited was transported within 30 min.Release of Cry j l from JCP reached maximum at 10 min.Threshold PP count for positive reaction was 67.1 _+ 16.2 (n=22).Intranasal PP were 22.6 +-45+1 (n=18) in JCP patients and 31.7 _ 58+3 (n=13) in controls.CONCLUSIONS: The majority of inhaled PP is deposited on the nasal mucosa and decreased by mucociliary transportation.During this process allergic reaction occurs leading to expelling of PP and then subsidence of symptom.When the number of PP deposited reaches the threshold again by further inhalation, symptom recurs.