Does a middle ear infection cause fluid build-up in the ears?

Fluid buildup in the ear is a frequent complication of middle ear infections. This buildup occurs when the Eustachian tube becomes blocked by mucus due to infection caused by cold or flu, according to KidsHealth.

The purpose of the Eustachian tube is to allow drainage of fluid produced within the middle ear; the Eustachian tube connects to the back of the throat for just this purpose, as MedlinePlus explains. While infection can lead to blockage of the tube, blockage of the tube for reasons such as allergies, overgrown adenoids, excess production of saliva and irritants such as tobacco smoke can conversely lead to middle ear infection.