Nasal physiology and inflammatory mediators during natural pollen exposure.

Nasal allergen challenges in allergic rhinitis subjects provoke characteristic alterations in nasal and eustachian tube (ET) function. The purpose of this study was to examine the effect of natural pollen exposure on nasal physiology and inflammatory mediators. Grass pollen counts, ET function (sonotubometry), nasal resistance (rhinomanometry), symptoms, mediator levels (saline wash), and skin test reactivity in nine adults with grass allergy were monitored weekly before (week 1), during (weeks 2 to 9) and after (weeks 10 and 11) grass pollen season. Pollen counts peaked at week 3, and then decreased gradually. Mean nasal resistance (cm H2O/L/sec) increased from a baseline of 2.4 +/- 0.5 to 3.7 +/- 1.1 at week 3, peaked at week 4 (5.3 +/- 1.2), remained elevated (weeks 5-8), peaked again at week 9 (6.6 +/- 1.4), and then decreased, Bilateral ET obstruction was not present in any of the subjects at baseline, but was present in five of the nine subjects at week 4. Symptom severity paralleled grass pollen counts. Peak mediator levels were observed at weeks 2 and 9 for histamine and at weeks 3 and 10 for leukotriene C4. Seasonal increases in grass and histamine-induced wheal sizes were also observed. These data show that measurable changes in the function of the nose and ET and the levels of nasal mediators and dermal reactivity accompany and track pollen counts during seasonal exposure and suggest that therapy for seasonal allergic rhinitis should be (1) directed at reducing airway inflammation and (2) continued well beyond the time of peak pollen exposure.