Recent studies in our laboratories have documented the development of allergic rhinitis (AR) and subsequent ET obstruction after provocative intranasal pollen or house dust mite antigen challenges in hypersensitive subjects. The induced ET obstruction was antigen dose dependent and inversely related to the patient's specific IgE antibody titer. Since prolonged ET obstruction underlies the pathogenesis of otitis media with effusion (OME), these data suggest a role for AR in the etiology of OME. To ascertain if ET obstruction and/or OME develop during natural pollen exposure, weekly bilateral ET function was measured by the 9-step pressure swallow tympanometric test. Eight children ages 5 to 14 years with documented ragweed AR and recurrent OME were studied before, during and after the 1984 ragweed season which was estimated by daily pollen counts. Ragweed allergy was confirmed by positive skin test with serum RAST ranging from 1 to 10 percent. Symptom score and medication diaries were kept. Whereas 9 of 16 ears (56%) showed normal ET function before pollen season and 10 of 16 (63%) after pollen season, only 2 of 15 (13%) had normal ET function at the peak of pollen season and 23 of 75 (30%) ears tested had normal ET function during the 5 week pollen season (p <0.05). OME did not develop in these patients. These studies have shown for the first time in children with a history of OME a causal relationship between an allergic reaction and the development of ET obstruction.