Otitis media is inflammation of the middle ear, or middle ear infection (the word otitis is Latin and it means “inflammation of the ear”, and media means middle).

Otitis media occurs in the area between the ear drum (the end of the outer ear) and the inner ear, including a duct known as the Eustachian tube. It is one of the two categories of ear inflammation that can underly what is commonly called an earache, the other being otitis externa. Diseases other than ear infections can also cause ear pain, including cancers of any structure that shares nerve supply with the ear.

Otitis media is very common in childhood, with the average toddler having two to three episodes a year, almost always accompanied by a viral upper respiratory infection (URI), mostly the common cold. The rhinoviruses (nose viruses) that cause the common cold infect the Eustachian tube that goes from the back of the nose to the middle ear, causing swelling and compromise of pressure equalization, which is the normal function of the tube. In general, the more severe and prolonged the compromise of Eustachian tube function, the more severe the consequences are to the middle ear and its delicate structures. If a person is born with poor Eustachian tube function, this greatly increases the likelihood of more frequent and severe episodes of otitis media. Progression to chronic otitis media is much more common in this group of people, who often have a family history of middle ear disease.