Allergy increases susceptibility to otitis media with effusion in a rat model

To investigate the possible relationship between allergy and otitis media w ith effusion (OME), we investigated the hypothesis that allergen presentati on to the middle ear causes functional disruption of the eustachian tube pr edisposing to the development of OME. Thirteen of 19 Brown-Norway rats were sensitized to ovalbumin, and the remaining 6 served as nonallergic control s. To mimic subclinical exposure to allergen, we transtympanically injected ovalbumin at a dose (0.01 mg) that produced no changes detectable by otolo gic examination. Next, both allergic and nonallergic rats were exposed to t ranstympanic injection of either low-dose (10 mu g/mL) or high-dose (100 mu g/mL) lipopolysaccharide to simulate bacterial exposure. The allergic rats were found to have larger middle ear effusions when exposed to high-dose l ipopolysaccharide as compared with the nonallergic controls. This response could be inhibited by diphenhydramine. We conclude that allergen presentati on to the middle ear of allergic rats causes eustachian tube dysfunction pr edisposing to OME.