Causes of otitis media

The middle ear is connected to the throat by a small tube called the eustachian tube. It's protected from the outside by a thin shield called the tympanic membrane, or eardrum. Viruses and bacteria that normally live in the throat can sometimes cross into the middle ear through the eustachian tube, causing an infection.

Winter is high season for ear infections. They often follow a cold. Some factors that increase a child's risk for middle ear infections include:

• crowded living or daycare conditions
• exposure to secondhand smoke
• respiratory illnesses
• close contact with siblings who have colds or ear infections
• having a cleft palate
• allergies that cause congestion on a chronic basis

Barometric trauma is another risk factor for a middle ear infection. The pressure in the middle ear rises when the airplane you are travelling on descends or when you ascend while scuba diving. If the eustachian tube is not open, the pressure in the middle ear cannot be equalized, and thus, may cause injury, which increases the risk of an acute ear infection.