To understand earaches you must first know about the Eustachian tube, a narrow channel connecting the inside of the ear to the back of the throat, just above the soft palate. The tube allows drainage — preventing fluid in the middle ear from building up and bursting the thin ear drum. In a healthy ear, the fluid drains down the tube, assisted by tiny hair cells, and is swallowed.
The tube maintains middle ear pressure equal to the air outside the ear, enabling free eardrum movement. Normally, the tube is collapsed most of the time in order to protect the middle ear from the many germs residing in the nose and mouth. Infection occurs when the Eustachian tube fails to do its job. When the tube becomes partially blocked, fluid accumulates in the middle ear, trapping bacteria already present, which then multiply. Additionally, as the air in the middle ear space escapes into the bloodstream, a partial vacuum is formed that absorbs more bacteria from the nose and mouth into the ear.