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Middle Ear Infections

What Causes Middle Ear Infection?

Last modified: 
19/04/2012 - 15:06

Contributing Author: Guy Slowik FRCS

Many factors play a role in whether your child will get an ear infection.

The Role Of The Eustachian Tube

Ear infections almost always begin with swelling of the eustachian tube, usually because of exposure to bacteria, viruses, smoke, or allergens. When the eustachian tube is swollen, normal fluids formed in the middle ear cannot flow into the nose and throat.

  • The eustachian tube may also become plugged when the normally thin, clear mucus made by the lining of the nose and middle ear becomes thickened, such as when your child has a cold.
  • In infants and young children, the eustachian tube is shorter, narrower, and less rigid than in older children and adults, making it easier for bacteria from a cold to pass from the back of the nose and throat into the middle ear. In addition, a child's narrower eustachian tube is more likely to become obstructed.
  • When the eustachian tube swells and closes, it traps infected fluid in the middle ear and creates a breeding ground for germs.

Bacteria And Viruses

The most common bacteria that cause ear infections includeHaemophilus influenzae (which is associated with respiratory infections in children), and Streptococcus pneumoniae (also called pneumococcus). Less common bacteria include Moraxella (Branhamella) catarrhalis and Streptococcus pyogenes.

Viruses such as respiratory syncytial virus (responsible for lower respiratory infections) and influenza viruses play an indirect role in ear infection by causing inflammation in the nasal passages and a stuffy nose, with thick mucus. Rhinovirus, which causes the common cold, has been found in one to eight percent of otitis media cases.

Allergies

Allergic rhinitis is the runny nose, itching, and sneezing some people experience when exposed to an allergen, such as pollen or animal hairs. It is unclear whether allergic rhinitis actually causes middle ear infections. However, allergies that cause the nasal passages to become inflamed and congested, such as hay fever, seem to increase the likelihood of acute otitis media.

A Child's Other Health Problems

Certain health problems increase the likelihood that a child will develop middle ear infections. For example, children with breathing disorders such as asthma have more ear infections than healthy children. The same is true of those with allergies and sinusitis.

Children with more complicated medical problems, such as Down's syndrome, cleft palate, or illnesses that suppress the immune system, are also at higher risk for ear infections.

Lifestyle

The incidence of ear infections has been on the rise in the U.S., in part because of the way many families live. Lifestyle risk factors for middle ear infections include the following:

  • Attendance in day care centers (where young children are exposed to the respiratory infections that often happen before an ear infection)
  • Exposure to second-hand smoke
  • Formula-feeding (because formula does not provide the immune-system protection present in mother's milk)
  • Baby's position during bottle-feeding (because eustachian tubes do not function as well when your baby is lying flat while sucking, compared to when he is held with his head up )
  • Pacifiers (because sucking may increase production of saliva, which serves as a vehicle for bacteria that can travel up the eustachian tubes to the middle ear)

How-To Information:

Preventing ear infections

Although they are not foolproof, there are certain steps you can take to help prevent ear infections:

  • Breast-feed infants for at least 6 months.
  • Serve your family plenty of fruits and vegetables.
  • Make sure your family gets proper rest.
  • Wash hands frequently.
  • Reduce stress, which can weaken the immune system.
  • Consider annual flu vaccinations and a one-time vaccination against pneumococcal pneumonia.
  • Avoid exposure to smoking.

How To Information:

Warding off ear infections when your child has a cold

Children who get ear infections frequently when they have a cold can take the following precautions:

  • Take oral decongestants at the first sign of a cold.
  • Sleep with their head elevated on a few pillows.
  • Gargle with salt-water rinses.
  • Use spray decongestants cautiously to help keep the eustachian tube lining from getting so swollen that it stops functioning properly.
  • Avoid over-the-counter antihistamines, such as diphenhydramine or chlorpheniramine, for the treatment of colds because they thicken secretions.
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From Andrew Maynard - Chair of the University of Michigan Department of Environmental Health Sciences, with help from David Faulkner - 2013 Master of Public Health graduate.