The eustachian tube connects the throat and middle ear. You have two
tubes, one for each ear. This tube drains fluid from the middle ear into the
throat. It also helps keep pressure in the middle ear equal.
During a cold, sinus or throat infection, or an allergy attack, the
lining of the eustachian tube can swell and block the tube. Air can't move into
or out of the middle ear, so a vacuum effect occurs, which pulls fluid into the
middle ear. The fluid builds up in the ear because it can't drain down the
throat. Germs can grow in the fluid and cause an infection. This condition is
called acute otitis media (ear infection).
These tips may help you avoid getting swimmer's ear:
Be careful when cleaning your ears. Most doctors advise against using cotton swabs unless you're using it to clean the outside of the ear. Instead, wipe the outer ear with a clean washcloth. Do not dig into the ear canal, and never use a pointed object. Scratching the skin of the ear canal can let germs get in under the skin and cause infection.
Avoid earplugs, if possible. These can irritate the ear canal.
After swimming, tilt and shake...