What Causes an Ear Infection?

Known as acute otitis media, a wake forest ear infection affects the middle ear which is the pocket behind the eardrum that contains tiny vibrating bones.  Adults can develop middle ear infections thought the condition is more common in children.

Symptoms of an ear infection generally develop rapidly.  In children, symptoms may include ear pain, trouble sleeping, tugging on an ear, excessive crying, hearing difficulties, fever, drainage, loss of appetite, and headache.  Adults generally have ear pain, fluid drainage from the ear, and hearing difficulties.

What Causes Ear Infections?

Most ear infections are caused by a virus or bacterium that has invaded the middle ear.  Often the ear infection is due to another illness (flu, cold, or allergy) that leads to swelling and congestion of the throat, nasal passages, and eustachian tubes.

  • Role of the Eustachian Tubes:  A pair of thin tubes that connect the middle ear to the back of the throat, the eustachian tubes regulate air pressurization, pump fresh air into the ear, and drain normal middle ear secretions.  When these tubes swell, they can become blocked allowing fluid to build up within the middle ear.  The fluid may get infected and lead to the symptoms associated with an ear infection.  Because the tubes are more horizontal and narrow in children, they are harder to drain and more prone to clogging.
  • Role of Adenoids:  Believed to play a role in the immune system, adenoids are two small tissue pads located in the rear of the nose near the opening of the eustachian tubes.  When the adenoids become swollen, they can block the eustachian tubes leading to an ear infection.  Children have larger adenoids relative to adults so any irritation or swelling of the adenoids tends to contribute to ear infections.

Related Conditions:  Some middle ear conditions related to ear infections or that could result in problems include:

  • Otitis media with effusion or swelling in the middle ear lacking any viral or bacterial infection. This can occur if fluid buildup lingers despite the ear infection having cleared up.  Dysfunction or a noninfectious eustachian tube blockage can also contribute to the condition.
  • Chronic otitis media with effusion happens when fluid stays in the ear and continues to reoccur without a viral or bacterial infection. Can make children prone to new ear infections and could negatively impact hearing.
  • Chronic suppurative otitis media is an infection that does not go away despite the normal treatments. Can progress and cause a perforation in the eardrum.

Other Causes or Risk Factors

  • Age: Children ages 6 months to 2 years are at higher risk for developing ear infections due to the shape and size of their eustachian tubes and developing immune systems.
  • Group Daycare/Childcare: Because there are more people in a group that could carry infection, children in group child care settings are exposed to pathogens at a higher rate than those who stay home.
  • Infant Feeding: Bottle fed babies, especially those that feed while lying down, often have higher incidents of ear infections that breast fed babies.
  • Seasonal Factors: Fall and winter months tend to have the highest incident of ear infections.  Those with seasonal allergies tend to develop ear infections as pollen counts are elevated.
  • Poor Quality Air: Air pollution or tobacco smoke can increase ear infection risk.
  • Cleft Palate: Because muscles and bone structures in children with cleft palates are different, they may make eustachian tube drainage more difficult.

More on Ear Infections : How Long Do Ear Infections Last?