What causes middle ear infections?
Most cases of middle ear infections start with a viral infection, such as that which causes a cold or the flu. Infection spreads from the nose and throat to the middle ear through a connecting passage, known as the eustachian tube. In turn, the eustachian tube becomes blocked, which prevents excess mucus from draining away as normal. Less commonly, the eustachian tube is blocked by something else, such as a structural abnormality, allergy or irritation from tobacco smoke. Infection occurs when micro-organisms thrive and reproduce in the stagnant fluid.