Middle Ear Infections

Next to the common cold, ear infections are the most commonly diagnosed childhood illness in the United States. More than three out of four children have had at least one ear infection by the time they reach 3 years of age. To understand how ear infections develop, it's important to first understand how the ear works.

A Close Look at the Ear

Think about how you can feel speakers vibrate as you listen to your child's favorite CD in the car or how you feel your throat vibrate when you speak. Sound, which is made up of invisible waves of energy, causes these vibrations. Every time you hear a sound, the various structures of the ear have to work together to make sure the information gets to your brain.

The ear is responsible for hearing and balance and is made up of three parts - the outer ear, middle ear, and inner ear. Hearing begins when sound waves that travel through the air reach the outer ear, or pinna, which is the part of the ear you can see. The sound waves then travel from the pinna through the ear canal to the middle ear, which includes the eardrum (a thin layer of tissue) and three tiny bones called ossicles. When the eardrum vibrates, the ossicles amplify these vibrations and carry them to the inner ear.

The inner ear translates the vibrations into electric signals and sends them to the auditory nerve, which connects to the brain. When these nerve impulses reach the brain, they're interpreted as sound.

To function properly, the middle ear must be at the same pressure as the outside world. This is taken care of by the eustachian tube, a small passage that connects the middle ear to the back of the throat behind the nose.

By letting air reach the middle ear, the eustachian tube equalizes the air pressure in the middle ear to the outside air pressure. (When your ears "pop" while yawning or swallowing, your eustachian tubes are adjusting the air pressure in your middle ears.) The eustachian tube also allows for drainage of mucus from the middle ear into the throat.

Sometimes, the eustachian tube may malfunction. For example, when a child has a cold or an allergy affecting the nasal passages, the eustachian tube may become blocked by congestion in its lining or by mucus within the tube. This blockage will allow fluid to build up within the normally air-filled middle ear. Bacteria or viruses that have entered the middle ear through the eustachian tube can also get trapped in this way. These germs can breed in the trapped fluid, eventually leading to an ear infection.

About Middle Ear Infections (Otitis Media)

Otitis media refers to inflammation in the middle ear area. There are different forms of otitis media. Typically, when the doctor refers to an ear infection, he or she is most likely talking about "acute otitis media" (although there's also the common ear infection called swimmer's ear, or otitis externa).

Acute otitis media is the presence of fluid, typically pus, in the middle ear with symptoms of pain, redness of the eardrum, and possible fever.