The middle ear is the space behind the eardrum, which is connected to the back of the throat by a passageway called the Eustachian tube. Middle ear infections, also called otitis media, can occur when congestion from an allergy or cold blocks the Eustachian tube. Fluid and pressure build up, so bacteria or viruses that have traveled up the Eustachian tube into the middle ear can multiply and cause an ear infection.
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