Middle ear infection (otitis media) - Causes 

Causes of Middle ear infection 

Most cases of otitis media (middle ear infection) are caused when a bacterial or viral infection, such as a cold, spreads into a part of the ear known as the Eustachian tube.

The Eustachian tube is a thin tube that runs from the middle ear to the back of the nose. It has two main functions, the first, to ventilate the middle ear, helping to maintain normal air pressure. The second, to help drain away mucus and other debris from the ear.

An infection in another part of the body can cause the Eustachian tube to become blocked, leading to an infection.  

Enlarged tonsils or adenoids (small lumps of tissue at the back of the throat, above the tonsils) may block the Eustachian tube. Adenoids and tonsils can be removed if they cause a persistent or frequently reoccurring ear infection, this is more common in children than in adults.

Read more about removing tonsils and removing adenoids.

A child's Eustachian tube is smaller than an adult's, which makes it more likely to become blocked. A child’s adenoids are much larger than an adult’s in relative terms.

Other things that can increase the risk of developing an ear infection include:

  • attending a nursery or day care centre – this increases a child’s likely exposure to infection from other children
  • being exposed to tobacco smoke (passive smoking)
  • not being breastfed

Page last reviewed: 23/04/2012

Next review due: 23/04/2014


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