Most cases of middle ear infection (otitis media) are caused when a bacterial or viral infection, such as the 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. Its two main functions are to ventilate the middle ear, helping to maintain normal air pressure. It also helps to 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, which 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 make 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 smoking (passive smoking)
- not being breastfed
