Causes of Ear Infections


When I wash my 3 month old baby's hair, I usually get soap and water in his ears. Will this cause an ear infection? What causes an ear infection?

Dr. Greene's Answer

Your question is a timely one, since ear infections are most common in winter or early spring, and the highest incidence is in children under 2 years old. In the United States, there are over 25 million visits to pediatricians each year related to ear infections, making it the most common diagnosis for children.

Otitis media is an infection in the space behind the ear drum. Soap or water or bacteria that enters the ear from the outside can’t get into this space to cause an infection. Bacteria enters the middle ear through the Eustachian tube, a narrow channel that connects the inside of the ear to the back of the throat, just above the soft palate. Clearly this tube does not exist simply to provide a secret passage for bacteria. What is its function?

(Does anybody know what ‘Eustachian’ means? Amaze friends at parties — Bartolommeo Eustachio was the Italian anatomist who discovered this troublesome structure. The name doesn’t tell us anything about what it does, only who discovered it. He died in 1574, never guessing that you and I would be discussing his tube on the World Wide Web! )

The tube is an intermittent drainage conduit to prevent the secretions that are normally made in the middle ear from building up and bursting the thin ear drum. Instead they drain down the tube and are swallowed. Tiny hair cells in the tube propel this mucus blanket like a conveyer belt to carry bacteria down the drain. The tube also functions to keep the air space in the middle ear at the same pressure as the air around us. In this way the eardrum can move freely, and our hearing is most effective.

When all is well, the tube is collapsed most of the time in order to protect the middle ear from the many organisms that live in the nose and mouth. Only when you swallow does a tiny muscle open it briefly to equalize the pressures and drain the ear secretions. If any bacteria make it into the ear, the drainage mechanism, helped by the little hair cells, should flush it out.

Ear infections are the result of Eustachio’s tube not performing its job. When the tube is partially blocked, fluid accumulates in the middle ear. Bacteria already there are trapped and begin to multiply. Air in the middle ear space escapes through the thin lining into the bloodstream, producing a partial vacuum. This sucks more bacteria from the nose and mouth into the ear. If the tiny hair cells are damaged (as by a cold virus), the mucus blanket can’t help move the bacteria out.

So, what blocks the tube? Respiratory infections, irritants especially cigarette smoke and allergies can all inflame the lining of the tube, producing swelling and increased secretions. They can also cause enlargement of the glands near the opening of the tube, blocking flow at the outlet. Sudden increases in air pressure (during descent in an airplane or on a mountain road) can both squeeze the floppy tube closed and create a relative vacuum in the ear. Drinking while lying on one’s back can occlude the slit-like tube opening. The last two decades of the 20th century have seen a dramatic rise in ear infections largely due to increased pollution and the prevalence of early childhood day care (where children are exposed to many respiratory infections).

Small children get more ear infections than older children or adults for several reasons: The tube is shorter, more horizontal, and straighter, (quick and easy trip for the bacteria). The tube is floppier, with a tinier opening (easier to block). And young children get more colds (it takes time for the immune system to be able to recognize and ward off cold viruses).

Ear infections happen when Eustachio’s tube is blocked. Although a myriad of factors can lead to a blocked tube, getting water in your baby’s ears won’t. Enjoy bath time!

Last medical review on: May 19, 2008
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Dr. Greene is a practicing physician, author, national and international TEDx speaker, and global health advocate. He is a graduate of Princeton University and University of California San Francisco.
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Recent Comments

I have a question. We live on a farm and have a very shallow hand dug well, dyg many many years ago. I had the well tested a few years ago and it was found to contain coliform of unknown origin. We had cattle at that time. Also the well is in the center of the barn. My granddaughter now lives in that home and they use that well water. Is it possible the bacteria/coliform is causing my two year old granddaughter’s ear infections? I plan on having the well tested again but would appreciate your opinion now. Is this well water safe to bath in, as far as her ears go ? Thank You

Hi Mary,

This is a great question and I don’t have the answer (I”m not a doctor, and perhaps one of the doctors that come here will chime in). But I did grow up on a farm with well water.

Having the water checked is very wise. Even deep wells that have untreated water can become polluted.

In the interim, there are excellent ways to filter water. The best we’ve found for drinking is the Berkey system. We have one sitting on our countertop and use it for all our drinking water at home. I believe they also sell filters for showers.

Even if the water isn’t causing ear infections, it could present other health hazards for the family. It’s great you’re being proactive.

Co-founder & Executive Producer,

My son (7weeks) has what seems to be like wet ears, from the inside to behind the ear is some what wet even if I dry it off it goes back to the same way, when he sleeps on one side the ear gets dry but it drys to be crusty, seems like it’s starting to be painful cause he crys with his hands by his ears, not sure what it is but is it an ear infection? Please help!

I took my 14 old month to the pool and some pool water got inside his ear from splashing.. as soon as the water got inside he complaint and showed me his ear, I kind of turned him sideways and did a little jumping so the water would come out. But I am afraid he might develop an ear infection he keeps touching it and at night when he is sleeping he moans like in pain… should I wait or do something before it gets worse?
Please help, thanks in advance!!

My son is 14 month old now and was a healthy baby all around. By his birthday he started daycare and ever since he is sick every other week. His colds never go away. He had ear iinfections twice and treated with antibiotics, still sick with runny cough and holds his ear most of the time. What should I dO? Please help.

Our 4.5 month old was diagnosed with his second ear infection in the last 18 days. He will go on the second round of antibiotics. My worry is that it will kill off all the good gut bacteria. Can I give a 4.5 month old yogurt, to replenish it? What kind and how much is okay to give? Are there are other form that probiotics come in that a 4.5 month old can ingest?

Please help.

Thank you

I’m going through the same thing with my 6 month old son. He is on his third ear infection now. He started at 2 months with ear infections. May I ask how your baby is doing now?

Dr. Greene has information about probiotics for mom and baby that you will likely find helpful — Dr. Greene says most 4.5 month old babies can take probiotics.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

I think that this is probably the best answer that I had regarding water in the ear during bath time of my baby. Thank you so much for excellent explanations!!!

how do you get a ear infection

Swelling and a drop of blood makes me wonder about some kind of insect bite in the ear, rather than a typical ear infection. But having 4 real ear infections already in a 4-month old should be looked into to figure out why. Ask the doctors not just to treat the current infection, but to answer why so often. Most babies don’t get many ear infections before 6 months old.