Causes of Ear Infections

The middle ear is the part of the ear that is enclosed behind the eardrum. A tiny tube, called the eustachian tube, drains any fluids from the middle ear into the throat. Colds and episodes of allergic runny nose, due to airborne allergens or allergies to cow’s milk or other foods, block this eustachian tube with mucus and inflammation. When this tiny mucous-membrane-lined canal is closed off, inflammatory fluids build up in the middle ear cavity (serous otitis media), sometimes referred to as effusion. Over time, passage of nasal and throat bacteria into this tube, from pacifier use or especially when a child is lying on his back, can seed the middle ear. Bacteria can then multiply to large numbers when finding a friendly fluid-filled middle ear environment, creating painful infection (acute otitis media).