There are three regions of the ear: the outer ear, which includes the ear canal and the eardrum; the inner ear, which contains the sound-sensing apparatus; and in between them is the middle ear, a chamber with three small bones to help amplify sound. The middle ear is a sealed chamber, except for the presence of a small tube called the Eustachian tube (or auditory tube). This tube connects the middle ear to the back of the nasal cavity and allows air to enter or leave when it is necessary to equalize the pressure inside and outside the middle ear. This is the same reason that swallowing or chewing gum helps “pop” your ears when you ascend to high altitude or fly on an airplane: the motion of your jaw opens the Eustachian tube and allows air to enter or leave.

When an infection occurs in the upper respiratory tract (the nose and/or throat) such as the common cold, it can spread to the Eustachian tube. The inflammation that results may block the Eustachian tube. Without normal air circulation between the nose and inner ear, the pressure there may decrease; this along with other changes allows the infection to spread into the middle ear. The infection can cause fluid and pressure to build up in the middle ear leading to pain and dampened hearing. Some people are born with Eustachian tubes that don’t work as well as they should and this makes them prone to repeated ear infections during childhood.

So why do children get ear infections so much more commonly than adults? For one, the Eustachian tubes in children are narrower and shorter than those of an adult, making it easier for viruses or bacteria to enter the middle ear and also making it easier for them to become blocked. Also, the adenoids in the upper throat tend to be larger and are more prone to infection in children. The adenoids can block the entrance to the Eustachian tubes, allowing fluid to build up in the middle ear. Finally, children are still developing their immune systems and so are more prone to the upper respiratory infections that can lead to ear infections.