Ear infections are conditions that involve infection and often inflammation of different areas of the ear. They most often result from viral, fungal or bacterial infection. In most cases, ear infections are not serious and clear on their own. However, bacterial infections may require treatment with antibiotics. Left untreated, these infections may lead to serious complications, particularly for young children.

Ear infections can occur in the outer, middle and inner ear. 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 (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.

Most ear infections occur in the outer or middle ear – inner ear infections are rare. Ear infections are not contagious. However, the viral infections (e.g., colds, the flu) that may precede them are contagious and can lead to ear infections. Ear infections are much more common in children than adults because their eustachian tubes are shorter and narrower, making them more difficult to drain. In addition, the adenoid tissue in the back of the throat is larger and may block the eustachian tubes.

Left untreated, ear infections sometimes can cause more serious complications. These may include:

• Ruptured eardrum. Can ccur when the eardrum perforates due to the pressure of fluid within middle ear. After rupture, fluid drains out of the ear canal, relieving pressure and pain in the middle ear. Surgery may be necessary to repair the perforation, although ruptures usually heal on their own. Ruptures occur infrequently and hearing is not usually impaired.
  
  
• Additional ear infections. Untreated middle ear infections can rupture an eardrum, resulting in the leakage of pus into the ear canal and causing an infection of the outer ear. In addition, untreated outer ear infections can result in recurring infections.
  
  
• Cellulitis. An infection of the skin surrounding the external ear. Outer ear infections that are untreated or do not respond to treatment may recur and lead to cellulitis.
  
  
• Cholesteatoma. Buildup of cellular debris in the middle ear. This is usually the result of chronic ear infections. It may cause damage to structures within the middle ear.
  
  
• Structural damage inside the ear. The small bones of the middle ear and other structures in the ear may become damaged if a middle ear infection is left untreated and fails to spontaneously resolve.
  
  
• Permanent hearing loss. This can occur once there is structural damage to the middle ear. It can also occur with inner ear infections. Children who experience hearing loss, even temporary hearing loss, at a young age may have difficulties in language acquisition and speech development.
  
  
• Acute mastoiditis. Occurs when ear infection spreads to the mastoid bone behind the ears. This complication is uncommon and is usually the result of a middle ear infection.
  
  
• Meningitis. Infection that causes inflammation of the membranes covering the brain and spinal cord. This may occur as a result of an ear infection and is a serious and potentially deadly disorder.