Most ear-related problems encountered during childhood involve infections. Ear infection is the second most commonly diagnosed childhood illness in the United States (after the common cold), according to the American Academy of Family Physicians (AAFP). Other ear-related conditions that affect children include those that result from objects or materials lodged in the ear and trauma to the ear.

Ear infections can occur in the outer, middle and inner ear. The majority of ear infections during childhood occur in the middle ear. Many children experience recurring ear infections.

The outer ear is the visible part of the ear. It includes the entire exterior ear (auricle), which is made up of cartilage and skin, and the earlobe. The outer ear also includes the ear canal (passageway that carries sound from outside the body to the eardrum). The eardrum (tympanic membrane) is a thin membrane located at the innermost end of the ear canal that separates the outer and middle ear.

The middle ear is the small, pea-sized chamber located just behind the eardrum. It is normally filled with air that enters the area via the eustachian tubes or auditory tubes (canals that go from the back of the nose and throat to the middle ear). The eustachian tubes (sometimes called auditory tubes) prevent pressure from building up in the ears. They generally remain closed, but open during swallowing or yawning to balance the air pressure in the middle ear with the air pressure outside the ear. The middle ear also contains tiny bones that send vibrations from the eardrum to the inner ear.

The inner ear consists of the cochlea (structure that contains the organ necessary for hearing) and the labyrinth (interconnecting cavities that help maintain balance). Nerve endings in the inner ear convert sound vibrations into signals to the brain that allow hearing to occur.

Infection occurs in the outer ear when the ear canal is exposed to excess moisture that causes an overgrowth of the bacteria and fungi that normally exist within the ear canal. Skin can become soggy, diluting the acidity normally present in the lining of the ear canal that helps to prevent infection. This can lead to inflammation of the ear canal that may extend to the outer ear, causing pain. Fluid may also become trapped in the ear canal due to a buildup of earwax (cerumen).

Although commonly called swimmer’s ear, outer ear infections can also occur when bacteria penetrate and infect the ear through any type of cut in the lining of the ear canal. This may be the result of a scratch or abrasion from objects placed into the ear canal. It can also occur from exposure to irritating chemicals (e.g., hairspray, hair dye) or contaminated water. 

Infection occurs in the middle ear when viruses or bacteria cause the eustachian tubes to swell and become blocked. Without air traveling to or from the middle ear, pressure inside the ear increases. This can be extremely uncomfortable and may feel as if the ear is a blown-up balloon, ready to pop. Middle ear infections also cause fluid accumulation and pus production within the middle ear. This may restrict the ability of sound vibrations to travel from the eardrum to the inner ear, causing temporary hearing loss.

In addition, the eardrum may turn pink or red, and fluid buildup and pus produced in the middle ear may press against the eardrum, causing it to stretch tightly or to bulge and become immobile. However, fluid buildup in the middle ear may also occur without an infection, often as the result of excess fluid produced during a previous episode of a cold or the flu.

Inner ear infections are rare. They occur when viruses or bacteria cause inflammation of the cochlea or labyrinth, resulting in dizziness and hearing loss. Viral causes of inner ear infection include the measles, mumps and flu. Bacterial inner ear infections can occur when a middle ear infection spreads to the inner ear.  

Young children are more susceptible to ear infections than adults because the immune system is not fully developed until about age 7. In addition, children have different size structures within the ear, nose and throat that are more likely to lead to pressure and fluid buildup in the middle ear. For example, their eustachian tubes are small and narrow, and they are more easily clogged. These tubes are horizontal in young children, so viruses or bacteria can be easily transferred from the nose to the middle ear. Adenoids at the back of the upper throat (near the eustachian tubes) are large in children, which can interfere with opening of the tubes and contribute to pressure buildup in the middle ear.