The link between allergic rhinitis and otitis media.

Past studies implicated allergy in the pathogenesis of otitis media. However, definitive proof of the assertion is lacking. Epidemiologic studies, including one recently published by Rylander and Megevand, consistently identify allergy as a risk factor for otitis media. Also, higher than expected frequencies of allergy are reported for patients with otitis media, but it is unclear if this is an epiphenomenon associated with referral bias. This possibility is exemplified by the results of two reviewed papers where Velepic and colleagues reported a 25% prevalence of allergy in otitis media patients while Alles and colleagues reported a prevalence of 89%. Other studies documented biochemical components of allergic inflammation in the effusions recovered from children with otitis media, and Hurst and colleagues published a recent paper continuing on that theme. However, it is not known if a local allergic reaction is required for the production of these components and if they are produced exclusive of other inflammatory products. Three published studies explored mechanisms by which allergy could cause otitis media. Tikkanen and colleagues reexamined at age 10 a group of 56 subjects with previously diagnosed milk allergy and showed that despite decreased reactivity to milk protein a high prevalence of otitis media was retained. This suggests that it is the allergic condition, not the specific allergy to milk that increases otitis media risk. Downs and colleagues exposed the middle ears of rats to histamine and provoked changes in the pressure regulating and clearance functions of the Eustachian tube. Those changes could prolong an otitis media episode, but middle ear histamine is not limited to the allergic condition. Gentile and colleagues challenged the nose of allergic and nonallergic subjects with histamine followed by interleukin-6 or placebo and measured nasal, pulmonary, Eustachian tube and middle ear functions. Interleukin-6 did not change the Eustachian tube or middle ear functions but did cause increased secretions in allergic patients.