Definition of Otitis media with effusion:

Otitis media with effusion (OME) is when there is thick or sticky fluid behind the eardrum in the middle ear, but there is no ear infection.

Causes, incidence, and risk factors:

The Eustachian tube connects the inside of the ear to the back of the throat. This tube helps drain fluids to prevent them from building up in the ear. The fluids drain from the tube and are swallowed.

Otitis media with effusion (OME) and ear infections are connected in two ways:

• After most ear infections have been treated, fluid (an effusion) remains in the middle ear for a few days or weeks.
• When the Eustachian tube is partially blocked, fluid builds up in the middle ear. Bacteria that are already inside the ear become trapped and begin to grow. This may lead to an ear infection.

The following can cause swelling of the lining of the Eustachian tube, leading to increased fluid:

• Allergies
• Irritants (especially cigarette smoke)
• Respiratory infections

The following can cause the Eustachian tube to close or become blocked:

• Drinking while lying on your back
• Sudden increases in air pressure (such as descending in an airplane or on a mountain road)

Getting water in a baby's ears will not lead to a blocked tube.

OME is most common in winter or early spring, but it can occur at any time of year. It can affect people of any age, although it occurs most often in children under age 2. (It is rare in newborns.)

Younger children get OME more often than older children or adults for several reasons:

• The tube is shorter, more horizontal, and straighter, making it easier for bacteria to enter.
• The tube is floppier, with a tinier opening that's easy to block.
• Young children get more colds because it takes time for the immune system to be able to recognize and ward off cold viruses.

The fluid in OME is often thin and watery. It used to be thought that the longer the fluid was present, the thicker it became. ("Glue ear" is a common name given to OME with thick fluid.) However, it is now believed that the thickness of the fluid has more to do with the particular ear than with how long the fluid is present.