Fluid behind the ear, also known as serous otitis media (SOM) or otitis media with effusion (OME), is a build-up of mucus or liquid behind the eardrum without symptoms of an ear infection. The most common cause of fluid in the ear is an ear infection, which can be either viral, bacterial, or a combination of both. Other causes of fluid behind the ear include:

• Damage to the ear drum
• A foreign body in the ear
• Allergies
• Irritants (particularly cigarette smoke)
• Respiratory infections
• 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 babys ears

The Eustachian tube connects the inside of the ear to the back of the throat. This tube helps drain fluid to prevent it from building up in the ear. If the Eustachian tube is blocked, fluid builds up in the middle ear so that the eardrum cant move the way it should. Swallowing causes the Eustachian tubes to open, which can happen 3 to 4 times per minute. If an Eustachian tube is blocked, fluid builds up in the middle ear.

If you notice any fluid leaking from your ear, especially if you have a fever, hearing loss, or dizziness, or if your ear is red and swollen, see your doctor. You may be advised to keep your ears dry and not clean your ears with cotton buds or put anything into your ears.