An ear infection (also known as otitis media) is when the middle ear (the area behind the eardrum) has infectious fluid in it. It is diagnosed by a provider looking in the child’s ear with an otoscope to see if there is infection. An ear infection is caused by fluid getting trapped in the middle ear (the area behind the eardrum). The Eustachian tube connects the middle ear into the sinuses, which allows fluid to drain. Sometimes (often after an upper respiratory illness), the sinuses are inflamed, not allowing the fluid to drain, and allowing infection to occur. It is more common in children because their Eustachian tubes are horizontal. As we grow, they become more vertical, allowing fluid to drain more easily.