Ear Infections - Causes

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About 15% of AOM-causing bacteria are now believed to be resistant to the first-choice antibiotics.

Viruses. Rhinovirus is a common virus which causes a cold, and plays a leading role in the development of ear infections. It is not the direct infecting organism, however. But other viruses, such as respiratory syncytial virus (RSV, a virus responsible for childhood respiratory infections) and influenza (flu), may be the actual causes of some ear infections. Increasing evidence suggests that such viruses play a greater role in ear infections than previously believed. The theory rests on the significantly lower rates of ear infections in children who have received flu vaccines.

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Allergies. Allergies can cause inflammation in the airways, and contribute to ear infections.

Inborn Conditions that Predispose a Child to Middle Ear Infections

Genetic Factors. Several studies suggest that multiple genetic factors may make a child more susceptible to acute otitis media.

• Genetic susceptibility to certain bacteria may result in development of persistent and recurrent acute otitis media.
• Abnormalities in genes that affect the defense systems (cilia and mucus production) and the anatomy of the skull and passages would also increase the risk for ear infections.
• Abnormalities in genes that regulate a powerful immune factor called interleukin 1 have been identified in some patients with recurrent acute otitis media who did not have any allergic disorders. Interleukin-1 plays a major role in producing inflammation in tissues and cells during heightened immune activity. Abnormalities in interleukin production may possibly result in a persistent inflammatory response.

Researchers are hoping that these findings may encourage primary care doctors to closely monitor children who have a family history of unusually frequent or severe upper respiratory tract infections.

Medical or Physical Conditions that Affect the Middle Ear. Any medical or physical condition that reduces the ear's defense system can increase the risk for ear infections. Children with shorter than normal and relatively horizontal Eustachian tubes are at particular risk for initial and recurrent infections. Inborn structural abnormalities, such as cleft palate, or genetic conditions, such as Kartagener's syndrome in which the cilia (hair-like structures) in the ear are immobile and cause fluid build up, also increase the risk.