At a certain age, every child wonders what's inside his or her ears. The bold ones ask to look. Being a softy, I usually acquiesce, then prepare to wince as the speculum pokes me in a sensitive spot. Sometimes I tease the children about what I see inside - elephants, or bunny rabbits - but they know I am kidding.
If I want to really explain what's inside, I have to draw a picture. I show how the ear hole winds its way in; how it ends in a tiny circle of paper-thin skin called the ear drum, and how behind the ear drum there is a little pocket of air called the middle ear. I draw a tube leading from the middle ear to the back of the nose, and explain how it's a good thing that air can get in and out through the tube. What's not so good is that viruses and bacteria can make their way up the tube and set up housekeeping in the middle ear. The medical term, otitis media, simply means middle ear infection.
With my picture to point at, I can go on to explain why it is that getting water in the ear doesn't cause middle ear infections. The ear drum is waterproof, like all skin, as long as there isn't a hole in it. Water can wash in and out all day without bothering the middle ear. (But the skin in the canal that leads to the ear drum can become infected if it stays wet for too long - a condition called otitis externa, which usually gets better with ear drops.)
I can also explain how I can usually tell if there is fluid behind the ear drum (the drum bulges outward and refuses to move back and forth when I puff air at it). What I can't tell is whether the fluid has germs growing in it. The only way to tell for sure is to poke a needle through the ear drum, and send a sample of the fluid to the lab.
When researchers have done that, they have found that most ear infections are caused by viruses. Only about a third are caused by bacteria. The antibiotics used to treat ear infections only kill bacteria; they don't do anything to viruses. We've also learned that most ear infections - even the ones caused by bacteria - will go away by themselves, without any long-term harm. Overuse of antibiotics leads to antibiotic-resistant bacteria. On the other hand, antibiotics do often bring about quicker improvement in children with ear infections caused by bacteria.
The decision of whether or not to use antibiotics for an individual child's ear infection is one that the parents and I make together. I supply the data: what I have seen inside the ear, and the benefits and risks of antibiotics. The parents make the call, based on what's best for their individual children and families. Working as a team, we usually end up doing the right thing.