Many times, ear infection occurs because the eustachian tubes (one runs from each middle ear to the back of the throat) become clogged. The tubes purpose is to drain fluid and bacteria that normally occurs in the middle ear. If the eustachian tubes become blocked, fluid can build up and become infected.
Other causes for ear infection include anything that can lead to the eustachian tubes and upper airways becoming inflamed or irritated, or cause more fluids to be produced such as:
Colds and sinus infections
Tobacco smoke or other irritants
Infected or overgrown adenoids (swollen lymphatic tissue in the back of the nose)
Excess mucus and saliva produced during teething
Ear infection occurs most frequently in the winter. Ear infection is not contagious, but colds are and may spread among children, causing them to develop an ear infection.