Unilaterality of obstruction after acute nasal allergen provocation. Relation of allergen dose, nasal reactivity and the nasal cycle.

We examined unilaterality of obstruction after acute bilateral nasal allergen provocation in two groups of pollen-sensitive volunteers studied out of season. One group was challenged on one occasion with a threshold allergen dose and on another with placebo. We measured nasal airway resistance (NAR) unilaterally for 3.5 hr before the challenges and for 40 min after. Most subjects' noses had marked asymmetry of response. Over half showed marked obstruction on one side and none at all on the other side. The side which showed higher resistance and greater lability before challenge was typically more obstructed after. In a second group we compared responses to threshold and x 10 threshold doses. Threshold challenge produced results similar to those seen with the first group. After the higher allergen dose, there was some obstruction in the less responsive side and the rate of rise was much slower. Obstructive response after acute threshold allergen challenge is typically one-sided. This pattern may be related to the stage of the nasal cycle in which the challenge was delivered. Higher allergen doses produce more obstruction in the less responsive side but the response is still asymmetrical.