Ear-related conditions, such as ear infections, are very common, especially in children. Approximately 75 percent of children have an ear infection by their third birthday, and nearly half have three or more ear infections during this time, according to the National Institute of Deafness and Other Communication Disorders.

However, conditions such as allergic rhinitis produce mucus that can flow back into the eustachian tube, creating a blockage. The eustachian tube itself also can become inflamed, further closing the passageway. This prohibits air from reaching the middle ear, and keeps fluid from draining out.

When the eustachian tube is not working properly (eustachian tube dysfunction), bacteria can build up in the trapped fluid and cause infection or inflammation (otitis media). If infection is recurring, the condition is called chronic otitis media. Children are particularly prone to this condition, because their tubes are narrower and straighter than in adults. A child's eustachian tube is also positioned at an angle. This makes it easier for bacteria, viruses and allergens to enter through the throat.

In addition, a child's adenoids are larger than they are in adults. An infection can cause the adenoids, which are located near the eustachian tubes, to enlarge and interfere with the eustachian tube opening.

Over time, an infection in the middle ear can develop into a thick, sticky secretion that builds up and sticks to the auditory ossicles, three bones of the middle ear that are crucial to a person’s ability to hear. This condition is known as middle-ear disease (otitis media with effusion). As the secretion impairs the bones’ ability to conduct sound, a person's hearing may suffer a sharp decline.