How does an upper respiratory infection spread to the middle ear?

An upper respiratory infection spreads to the middle ear primarily through the eustachian tube, a narrow passage connecting the middle ear to the nasopharynx.123

The middle ear is lined with a mucous membrane that is continuous with the lining of the nose and throat. Because these membranes are connected, infections such as the common cold, influenza, or other illnesses like measles can travel along this tissue from the upper respiratory tract directly into the middle-ear cavity and mastoid air cells.132

When this occurs, it often results in otitis media, an inflammation of the middle ear lining. This pathway is particularly significant because the same allergic reactions or infections that affect the nasal passages can also afflict the middle ear, potentially leading to complications if the infection is not properly treated.21