Between your middle ear and your throat there is a passage called the eustachian tube. The eustachian tubes (you have one on each side) keep pressure from building up by letting air move in and out of your middle ear. When you were young, especially before you turned 3, the eustachian tubes were very small and less able to keep germs out.
The eustachian tubes get longer and usually work better in older kids, but they can still cause problems. If you have allergies or catch a cold, the eustachian tubes can get blocked up and let germs get in the middle ear. Then the number of germs can grow inside your middle ear and cause an infection.
You do not catch ear infections from other people, though you might catch a cold that then leads to an ear infection. If you have an ear infection, you might have ear pain, a fever, or trouble hearing.
at 10:25 AM on Jun. 1, 2011