What causes middle ear infections?

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Middle ear infections are caused by blockage or dysfunction of the eustachian tube which is the tube that drains fluid from the middle ear into the throat.  Fluid is normally produced in the ear and throat but does not build up unless the eustachian tube is blocked so that the fluid cannot drain.  Middle ear infections can be either serous which means fluid alone has accumulated in the middle ear or supprative which means pus has developed behind the ear drum.  Both viruses and bacteria can cause middle ear infections.

There are many causes of eustachian tube dysfunction/blockage.  First of all, in young children, the eustachian tube is short and straight so it is easier to block than in older children and adults who have a longer more angled eustachian tube.  In some families, there is hereditary dysfunction of the eustachian tube such that the tube does not drain fluid properly.  Obstruction is often caused by nasal congestion and discharge which occurs with common colds or bad nasal allergies.  Enlarged tonsils and adenoids can also put pressure on the eustachian tube causing obstruction.  Also, children who have parents that smoke have a ten fold greater chance of developing middle ear infections.  This is because smoke exposure causes the cilia, which are little hairs that move bacteria and foreign material out of the eustachian tube, to become paralyzed.

Middle ear infections are often related to viral infections such as the common cold, which are extremely common in children. When the Eustachian tube, which allows air to pass between the ear and the nasal passages, becomes obstructed (for example, with excess mucus from a cold), viruses and bacteria may grow in the space behind the eardrum. In children, this tube is more easily obstructed than it is in adults.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.