An ear infection is usually a bacterial infection of one or more parts of the ear. (The ear has three parts- the outer, middle, and inner ear. Outer ear refers to the external ear canal; Middle ear is the part just past the eardrum; inner ear is the part beyond which contains nerve endings.) The most common type in infection is of the middle ear, although outer ear infections occur more often in adults. Infections in one part of the ear rarely spread to other parts, although if there is a hole in the eardrum it's quite possible all parts can be infected at once.

The outer ear infection is commonly refered to as Swimmer's Ear. As the name suggests, it is usually caused by bacteria from water getting into the ear canal, which is a small, warm, dark place that's hard to clean. Bacteria love that kind of thing. They get in and grow, which causes itching and burning. Swimmer's ear is treated with eardrops and suction.

Middle ear infections are more complex. They're most often found in children, although it's not unheard of in adults. The middle ear is an airtight drum of sorts which converts sound waves to vibrations. It is connected to the sinus cavity through eustachian tubes, which keep the ear at more or less the same pressure as the outside air. (This is what allows your ears to pop on airplanes or underwater- without them your eardrums would explode at a change in pressure.) When the sinus cavity is full of infection, however, eustachian tubes don't work that well. The ears of children often aren't fully protected against infection since their tubes might not work as well as they should- the muscles that hold them may be weak, or they may not be fully formed. Infection spreads from the eustachian tube to the middle ear, where the bacteria go nuts, throwing little bacteria parties and eating whatever they can find in the inner ear. Probably earwax or something, I don't know. The drum then swells up and hurts like you would not believe. This type on infection will not heal on its own, and left untreated will eventually lead to hearing loss. (Hearing is often lost temporarily during the infection, but clears up after the fluid drains.)

Middle ear infections can be treated with antibiotics, which kills the bacteria. The fluid drains on its own in a short time. However, if it's not treated in time, the eardrum may burst. While this seems like it would be bad, it's actually not; the ear no longer has fluid in it, which is good. However, infection is likely to come back, and scar tissue will build up, which leads to hearing loss over time. Children with persistant ear infection may have to have surgery to implant tubes in the ears. This is usually a last resort, however. A small tube is placed in a small hole which is created in the eardrum. The tube either stays there or falls out over time, but either way it causes no damage or hearing loss.

Inner ear infections are very rare. It can affect hearing, balence... A whole lot of stuff. Your doctor will probably prescribe massive antibiotics and possibly surgery.

My experience with an ear infection:
I woke up at 3:30 this morning, screaming. There were bugs eating my ear, you see, from the inside. Little tiny ladybugs. They were on fire, also.

Eventually I woke up enough to realize that there were no combustable insects in my ear, that was just a dream. The pain, however, was real. I tried several things to stop the pain- pressure, no pressure, hot, cold, water, q-tips. It was all for naught. Finally I got my dad to take me to the ER (it was Sunday, my normal doctor was out playing golf.), where I got an antibiotic shot and more prescriptions than I've ever had in my life. I'm on vicodin for the pain, which isn't as interesting as dem bones says it is, Zithromax to kill the infection, and something else whose name I forgot to do something with the fluid.

I'm having trouble hearing with my right ear, and it's literally incredible pain. Other noders told me that they'd had ear infections lanced before, that is, cut open. The doctor I went to said that lancing isn't done anymore because it often fails to clear the whole ear of fluid, and the scar tissue that forms on the eardrum can cause hearing loss.

The best description I can think of for the pain is as follows. (I told this to my brother when he said I was faking.)

Take a small screwdriver. Heat it to about 300 degrees. Then, JAM it into your ear as FAR AS YOU CAN. Then, take a mallet and pound it in further.

That's one tenth as bad as the pain is.