Everything You Wanted To Know About Ear Infections – Part 1

February 18, 2013

Winter and ear infections go hand in hand. But did you ever wonder why? According to grandma, the reason is clear: little Johnny didn’t wear a hat. Or maybe too much bath water spilled into his ears.

No. That’s not quite right.

To understand the real reason kids get ear infections in the winter, we must focus our attention on the little tube connecting the back of the throat to the middle ear space—the eustachian tube. The job of the eustachian tube is to equalize the air pressure on the back side of the ear drum with the pressure on the front side. This keeps the ear drum flat and moving freely in response to sound waves.

Unfortunately, air isn’t the only thing capable of moving through the eustachian tube. Mouth bacteria can also make the trip. To prevent this from happening, the inside of the eustachian tube is lined with cilia-containing cells. Cilia are finger-like projections that sweep bacteria back toward the mouth, interfering with travel and preventing bacteria from taking up residence in the middle ear space.

But while this sounds good on paper, a common winter-time visitor can render it useless: the dreaded viral upper respiratory infection.

Also known as “flu bugs” and “the common cold,” respiratory viruses hijack cells lining the upper respiratory tract and turn them into virus-producing machines. The immune system detects this trickery and responds by destroying the viruses and their hijacked cells.

Remember those cilia-containing cells lining the eustachian tube? They become a casualty of the viral assault, providing an opportunity for mouth bacteria to traverse the tube and take up residence in the middle ear space.

But wait. Why doesn’t every kid get an ear infection following every cold virus?

The answer to this question lies in the length, shape, and stiffness of the eustachian tube.

Short, wide eustachian tubes allow more bacteria to travel than long, narrow ones do. And floppy tubes can seal shut with help from sticky mucus that accompanies viral infections. This results in bacteria becoming trapped in the middle ear space with no chance for escape back to the mouth.

These genetically-determined eustachian tube qualities are also the reason children “outgrow” their frequent ear infections. What’s really happening is their short, wide, floppy eustachian tubes are growing into long, narrow, rigid ones.

Once bacteria arrive in the middle ear, they reproduce like crazy and overwhelm the tiny space. The body’s immune system kicks in, destroying the bacteria and creating thick pus. The pus pushes on the ear drum, causing pain receptors to fire and, if there’s enough pressure, causing the ear drum to rupture with pus pouring out the external ear canal.

So that’s why ear infections occur. Not from hat deficiencies or bath water, but from a combination of genetics, viruses, and mouth bacteria. So when and how do we treat ear infections? What can parents do to prevent them? And what role do ear tubes play in the process? Stay tuned. We’ll cover these important questions in part 2 of our series.

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