Ear Infections - Causes

Allergies. Allergies can cause inflammation in the airways, and contribute to ear infections.

Inborn Conditions that Predispose a Child to Middle Ear Infections

Genetic Factors. Several studies suggest that multiple genetic factors may make a child more susceptible to acute otitis media.

Genetic susceptibility to certain bacteria may result in development of persistent and recurrent acute otitis media.
Abnormalities in genes that affect the defense systems (cilia and mucus production) and the anatomy of the skull and passages would also increase the risk for ear infections.
Abnormalities in genes that regulate a powerful immune factor called interleukin 1 have been identified in some patients with recurrent acute otitis media who did not have any allergic disorders. Interleukin-1 plays a major role in producing inflammation in tissues and cells during heightened immune activity. Abnormalities in interleukin production may possibly result in a persistent inflammatory response.

Researchers are hoping that these findings may encourage primary care doctors to closely monitor children who have a familyhistory of unusually frequent or severe upper respiratory tract infections.

Medical or Physical Conditions that Affect the Middle Ear. Any medical or physical condition that reduces the ear's defense system can increase the risk for ear infections. Children with shorter than normal and relatively horizontal Eustachian tubes are at particular risk for initial and recurrent infections. Inborn structural abnormalities, such as cleft palate, or genetic conditions, such as Kartagener's syndrome in which the cilia (hair-like structures) in the ear are immobile and cause fluid build up,also increasethe risk.

Causes of Otitis Media with Effusion (OME)

OME may occur spontaneously following an episode of acute otitis media. Susceptibility to OME may also be due to an abnormal or malfunctioning Eustachian tube that causes a negative pressure in the middle ear, which allows fluid to leak in through capillaries. Problems in the Eustachian tube can be due to viral infections, second-hand smoke, injury, birth defects (such as cleft palate), or genetic diseases that affect the defense systems, such as Kartagener's syndrome.

The Incidence of Ear Infections and Other Airway Problems

Increased diagnosis of other disorders and infections of the upper and lower airways, such as asthma, allergies, and sinusitis, have paralleled the rise in ear infections. For example, the same bacteria are often responsible for both ear infections and sinusitis. In one study, 38% of children with ear infections also had sinusitis, and other studies have reported that nearly half of children with OME have concurrent sinusitis. While these studies may have overestimated the extent of clinically important sinus disease, the association is significant, even if the causal relationships are unclear. Researchers are looking for common risk factors, such as:

Increase in Day Care Center Attendance. Although ear infections themselves are not contagious, the respiratory infections that precipitate them can pose a risk for children with close and frequent exposure to other children. Some experts believe that the increase in ear and other infections may be due to the higher attendance of very small children, including infants, in day care centers beginning in the 1970s. For children who had the condition for a long time, however, neither day care attendance nor any other risk factor, including a history of upper respiratory tract infections or family history of OME, appeared to be relevant. Attendance in day care centers, then, may explain part, but not all, of the current increase in ear infections and other upper airway disorders.
Increase in Allergies. Some experts believe thatanincrease in allergies is also partially responsible for the higher number of ear infections, which is unlikely to be related to day care attendance. Studies indicate that 40 - 50% of children over3 years old who have chronic otitis media also have allergic rhinitis (hay fever). Allergies are also associated with asthma and sinusitis.