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Causes
By Mayo Clinic staff
An ear infection is caused by a bacterium or virus in the middle ear. This infection often results from another illness — cold, flu or allergy — that causes congestion and swelling of the nasal passages, throat and eustachian tubes.
Role of eustachian tubes
The eustachian tubes are a pair of narrow tubes than run from each middle ear to high in the back of the throat, behind the nasal passages. The throat end of the tubes open and close to:
- Regulate air pressure in the middle ear
- Refresh air in the ear
- Drain normal secretions from the middle ear
Swelling, inflammation and mucus in the eustachian tubes from an upper respiratory infection or allergy can block them, causing the accumulation of fluids in the middle ear. A bacterial or viral infection of this fluid is usually what produces the symptoms of an ear infection.
Ear infections are more common in children, in part, because their eustachian tubes are narrower and more horizontal — factors that make them more difficult to drain and more likely to get clogged.
Role of adenoids
Adenoids are two small pads of tissues high in the back of the throat believed to play a role in immune system activity. This function may make them particularly vulnerable to infection and inflammation.
Because adenoids are located near the opening of the eustachian tubes, inflammation or enlargement of the adenoids may block the tubes, thereby contributing to middle ear infection. Inflammation of adenoids is more likely to play a role in ear infections in children because children have more active and relatively larger adenoids.
Related conditions
Conditions of the middle ear that may be related to an ear infection or result in similar middle ear problems include the following:
- Otitis media with effusion is inflammation and fluid buildup (effusion) in the middle ear without bacterial or viral infection. This may occur because the fluid buildup persists even after an ear infection has resolved. It may also occur because of some dysfunction or noninfectious blockage of the eustachian tubes.
- Chronic suppurative otitis media is a persistent ear infection that results in tearing or perforation of the eardrum.
- Otitis media (ear infection). National Institute on Deafness and Other Communication Disorders. http://www.nidcd.nih.gov/health/hearing/otitism.asp. Accessed June 21, 2010.
- Ramakrishnan K, et al. Diagnosis and treatment of otitis media. American Family Physician. 2007;76:1650.
- Gould JM, et al. Otitis media. Pediatrics in Review. 2010;31:102.
- Diagnosis and management of acute otitis media. Pediatrics. 2004;113:1451.
- Otitis media with effusion. Pediatrics. 2004;113:1412.
- Ear tubes. American Academy of Otolaryngology — Head and Neck Surgery. http://www.entnet.org/HealthInformation/Ear-Tubes.cfm. Accessed June 30, 2010.
- Benzocaine topical products: Sprays, gels and liquids — risk of methemoglobinemia. U.S. Food and Drug Administration. http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm250264.htm. Accessed Apr. 8, 2011.
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