Glue ear causes fluid to build up in the middle ear. It's one of the most common causes of impaired hearing in young children. It is also known as secretory otitis media, otitis media with effusion, or serous otitis media.
The middle ear
The middle ear is directly behind the eardrum. It's made up of three tiny lever-like bones that carry sound vibrations from the eardrum to the inner ear. A healthy middle ear should contain air and no fluid.
The middle ear is connected to the back of the nose by a narrow channel called the Eustachian tube. This tube normally remains closed, and will only open when you yawn or swallow. Any fluid that builds up in the middle ear can be drained away by this tube. It also helps to maintain the air pressure within the middle ear.
If the Eustachian tube becomes blocked or swollen, the vacuum of air that builds up can draw fluid into the middle ear cavity from the mucus that lines the rest of the ear. At first the fluid is thin and watery, but later it can become thick and glue-like.