Middle ear infections occur behind the eardrum. In many cases, both ears are affected. Middle ear infections are most common in young children, whose ear anatomy is not fully developed. Children under age 5, boys, bottle-fed infants and children in daycare run the greatest risk of infection. Although much less common, middle ear infections can also occur in older children and adults.

Middle ear infections can be painful and they tend to disrupt sleep- for you as well as for your child. But this isn't the full extent of the problem. Middle ear infections can also limit the eardrum's flexibility, reducing your child's ability to hear. This could make it harder for your child to learn to talk. Depending on when the hearing problem starts and long it lasts, your child's learning ability could be affected.

Middle ear infections are usually caused by bacteria or viruses. In young children these germs probably reach the middle ear by traveling the short length of the eustachian tube from the throat. Once in the middle ear, they multiply and spread. This irritates the delicate tissues lining the middle ear and eustachian tube. If the eustachian tube lining swells enough to block off the tube, air pressure drops in the middle ear. This pulls the eardrum inward, making it stiffer and less able to transmit sound.

Once the eustachian tube swells shut, moisture can't drain from the middle ear. Instead, fluid builds up in the chamber. This may raise pressure behind the eardrum, decreasing pain slightly. But if the infection spreads to this fluid, pressure behind the eardrum shoots way up. The eardrum is forced outward, becomes painful and may break.

If the eardrum doesn't break and the tube remains blocked, the fluid becomes chronic (an ongoing condition). As the acute (immediate) infection passes, the middle ear fluid thickens. It becomes sticky and takes up less space. Pressure drops in the middle ear once more. Inward suction stiffens the eardrum, affecting hearing. If the fluid is not removed, the eardrum may be stretched and damaged.