Infection: Ear infections can start with a bacterial or viral infection (such as those causing common cold). In such cases, the middle ear becomes inflamed from the infection, and fluid builds up behind the eardrum. Bacteria cause about 65-75% of all ear infections. The most common types are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Viruses that may lead to ear infections include the respiratory syncytial virus (RSV), the most frequent type found, followed by influenza (flu) viruses.

Eustachian tube problems: Ear infections also may be associated with problems such as swelling within the eustachian tubes, the narrow passageways that connect the middle ear to the throat. Normally these tubes equalize pressure inside and outside the ear. But a child's eustachian tubes are narrower and shorter than those of an adult. This makes it easier for fluid to get trapped in the middle ear when the eustachian tubes dysfunction or become blocked during a cold. This provides a perfect breeding ground for infection. Also, just as the mucus in the nose gets thicker and harder to expel, fluid within the ear can also become thick and difficult to drain.

Adenoids (tonsils): Another factor in ear infections is swelling of the adenoids (tonsils). These are tissues located in the upper throat near where the eustachian tubes connect. Adenoids contain lymphocytes, or types of white blood cells that normally fight infection. But sometimes the adenoids themselves get infected or enlarged, blocking the eustachian tubes. Infection in the adenoids can also spread to the eustachian tubes, causing ear infections.

Immune function: Children also do not have fully developed immune systems, so it is easier for them to develop many illnesses, including ear infections.

Middle ear infections are usually diagnosed using a health history, a physical exam, and an ear exam.

Pneumatic otoscope: If a middle ear infection is suspected, a healthcare provider will use a pneumatic otoscope (an instrument for looking into the ear that puffs air) to look at the eardrum for signs of redness or bulging. In the case of fluid buildup without infection (otitis media with effusion), the eardrum can look like it is bulging or sucking in. In both cases, the eardrum doesn't move freely when the pneumatic otoscope pushes air into the ear.

Tympanometry: Tympanometry tests the movement of the eardrum. The tip of a hand-held tool is placed just inside the ear. It changes the air pressure inside the ear. Then, the tool measures how the eardrum responds. If the air pressure is not appropriate, then a ruptured ear drum may be present.

Hearing tests: A hearing test is recommended for children who have fluid in one or both ears (otitis media with effusion) for more than three months. Hearing tests are done sooner if hearing loss is suspected.

Tympanocentesis: Tympanocentesis is performed when fluid stays behind the eardrum (chronic otitis media with effusion) or infection continues even with antibiotics. Tympanocentesis can remove the fluid. The doctor uses a needle to pierce the eardrum and suck out the fluid. A sample is usually tested for bacterial or viral growth. These tests reveal what kind of bacteria or virus is causing the infection and which medication is best for treatment. The child may need analgesia or sedation before this procedure due to this being an uncomfortable procedure. Analgesia can be used when indicated with acetaminophen, with codeine (Tylenol #3®), or with diazepam (Valium®) for sedation. Side effects include drowsiness and sedation after the procedure is completed.

Reflectometry: Reflectometry is used if the ear exam with a pneumatic otoscope does not indicate that fluid is behind the eardrum. The tip of a small handheld instrument is placed in the ear canal and sends off a sound. How the eardrum reacts to the sound tells the doctor if fluid is present.

Blood tests, including white blood cell counts, can be used to determine if the immune system is functioning properly.

Ear infections (otitis media) are often difficult to detect in kids because most children affected by this disorder do not yet have sufficient speech and language skills to tell someone what is bothering them. Common signs to look for include unusual irritability, difficulty sleeping, tugging or pulling at one or both ears, earache, fever, fluid draining from the ear, loss of balance, and unresponsiveness to quiet sounds or other signs of hearing difficulty such as sitting too close to the television or being inattentive. Fluid buildup in the middle ear also blocks sound, which can lead to temporary hearing difficulties. An older child or adult may complain verbally of an earache (ear pain).

If the pressure from the fluid buildup is high enough, it can cause the eardrum to rupture, resulting in drainage of fluid from the ear, which may include blood and thick, yellow pus. This releases the pressure behind the eardrum, usually bringing on relief from the pain.

Otitis media with effusion often has no symptoms at all. In some individuals, the fluid that is in the middle ear may create a sensation of ear fullness or "popping." As with acute otitis media, the fluid behind the eardrum can block sound, so mild temporary hearing loss can happen, although it may not be obvious.

Ear infections are also frequently associated with upper respiratory tract infections (such as colds), so signs and symptoms such as a runny or stuffy nose or a cough may be present. An ear infection is not contagious (able to be spread), but the cold that may have caused the infection can be. Symptoms of a middle ear infection (otitis media) often start two to seven days after a cold or other upper respiratory infection.

Duration: Acute ear infections usually clear up within one or two weeks. Sometimes, ear infections last longer and become chronic (long term). After an infection, fluid may stay in the middle ear. This may lead to more infections and hearing loss.

The signs and symptoms of acute otitis media may range from very mild to severe.

Many ear infections clear on their own with no complications. However, long-lasting or recurrent infections can be detrimental, leading to hearing loss.

Short-term hearing loss: Fluid buildup can temporarily affect hearing. The hearing loss occurs because it is more difficult for the eardrum and the bones in the middle ear to send sound vibrations through fluid. The average hearing loss is 25 decibels, approximately the same effects as using ear plugs.

Long-term hearing loss: Usually the fluid disappears on its own in a few weeks. But sometimes it remains in the middle ear for months, which can damage the eardrum and bones in the middle ear. Persistent middle ear fluid was once thought to contribute to speech or developmental delays, but researchers now say this is not true.

Ruptured eardrum: During ear infections, fluid and pus may press against the eardrum and be very painful. Sometimes the pressure ruptures the eardrum. If this occurs, a discharge (release) of pus and blood from the individual's ear may be seen. The rupture actually relieves the pain, and in most cases the eardrum heals on its own. If the eardrum ruptures repeatedly and does not heal, surgical repair may be needed.

Mastoiditis: Untreated ear infections may lead to a type of sinusitis (sinus inflammation) known as mastoiditis, which affects the mastoid bone of the skull in the temple area. Very rarely, infections can move from the ear to other parts of the head, including the brain. Death can occur in severe cases.

Experts recommend contacting a healthcare provider immediately if the individual has a severe injury to the ear, has sudden hearing loss, severe pain, drainage from the ear, or dizziness, seems to be very sick with symptoms such as a high fever (over 102 degrees Fahrenheit), and has redness, swelling, or pain behind or around the ear. A doctor should be seen if a person with an ear tube develops an earache or has drainage from the ear.

Age: Children between ages six and 18 months are the most susceptible to ear infections, although ear infections are common from ages four months to four years.

Group child care: Children cared for in group settings, such as classrooms or daycare, are more likely to get colds and ear infections than are children who stay home.

Air quality: Children with exposure to tobacco smoke or higher levels of air pollution are at higher risk of ear infections.

Family history: Genetics (heredity) seems to play a role in the susceptibility to ear infections. A child has a greater chance of developing ear infections if a parent or sibling was diagnosed with the condition.

Race: Native Americans and Eskimos from Alaska or Canada tend to have more ear infections than do Caucasians. Hispanic children are also more susceptible to ear infections than Caucasian and African American children. Differences in the number of ear infections due to race are possibly due to genetic factors that affect the shape of the auditory tube.

Gender: Boys are affected more commonly than girls, but no specific causative factors have been found. Male sex is a minor determinant of infection.

Feeding position: Babies who drink from a bottle while lying down tend to have more ear infections than do babies who are held upright during feedings. Breastfeeding should also be performed sitting or standing upright, not lying down.

Season: Ear infections are most common during the fall and winter, probably due to decreased humidity when home heating is used. Dry air tends to cause more viruses (colds and flu) and ear infections. Dry air can dry out nasal passages, making them more susceptible to viral penetration into the body.

Birth defects or other medical conditions: Babies with cleft palate, a condition where the bones in the roof of the mouth have not grown together properly, or Down syndrome (mental retardation) are likely to get ear infections.

Allergies: Allergies can cause long-term congestion (stuffiness) in the nose that can affect how the eustachian tube works. Blocking this tube, which leads from the ear to the throat, can cause fluid to build up in the middle ear.

Repeat colds and upper respiratory infections: Most ear infections develop from colds or other upper respiratory infections.