The onset of signs and symptoms of ear infection is usually rapid.

Children

Signs and symptoms common in children include:

• Ear pain, especially when lying down
• Tugging or pulling at an ear
• Trouble sleeping
• Crying more than usual
• Fussiness
• Trouble hearing or responding to sounds
• Loss of balance
• Fever of 100 F (38 C) or higher
• Drainage of fluid from the ear
• Headache
• Loss of appetite

Adults

Common signs and symptoms in adults include:

• Ear pain
• Drainage of fluid from the ear
• Trouble hearing

Middle ear

An ear infection is caused by a bacterium or virus in the middle ear. This infection often results from another illness — cold, flu or allergy — that causes congestion and swelling of the nasal passages, throat and eustachian tubes.

Role of eustachian tubes

The eustachian tubes are a pair of narrow tubes that run from each middle ear to high in the back of the throat, behind the nasal passages. The throat end of the tubes open and close to:

• Regulate air pressure in the middle ear
• Refresh air in the ear
• Drain normal secretions from the middle ear

Swollen eustachian tubes can become blocked, causing fluids to build up in the middle ear. This fluid can become infected and cause the symptoms of an ear infection.

In children, the eustachian tubes are narrower and more horizontal, which makes them more difficult to drain and more likely to get clogged.

Role of adenoids

Adenoids are two small pads of tissues high in the back of the nose believed to play a role in immune system activity.

Because adenoids are near the opening of the eustachian tubes, swelling of the adenoids may block the tubes. This can lead to middle ear infection. Swelling and irritation of adenoids is more likely to play a role in ear infections in children because children have relatively larger adenoids compared to adults.

Related conditions

Conditions of the middle ear that may be related to an ear infection or result in similar middle ear problems include:

• Otitis media with effusion, or swelling and fluid buildup (effusion) in the middle ear without bacterial or viral infection. This may occur because the fluid buildup persists after an ear infection has gotten better. It may also occur because of some dysfunction or noninfectious blockage of the eustachian tubes.
• Chronic otitis media with effusion, occurs when fluid remains in the middle ear and continues to return without bacterial or viral infection. This makes children susceptible to new ear infections and may affect hearing.
• Chronic suppurative otitis media, an ear infection that doesn't go away with the usual treatments. This can lead to a hole in the eardrum.

Risk factors for ear infections include:

• Age. Children between the ages of 6 months and 2 years are more susceptible to ear infections because of the size and shape of their eustachian tubes and because their immune systems are still developing.
• Group child care. Children cared for in group settings are more likely to get colds and ear infections than are children who stay home. The children in group settings are exposed to more infections, such as the common cold.
• Infant feeding. Babies who drink from a bottle, especially while lying down, tend to have more ear infections than do babies who are breast-fed.
• Seasonal factors. Ear infections are most common during the fall and winter. People with seasonal allergies may have a greater risk of ear infections when pollen counts are high.
• Poor air quality. Exposure to tobacco smoke or high levels of air pollution can increase the risk of ear infections.
• Alaska Native heritage. Ear infections are more common among Alaska Natives.
• Cleft palate. Differences in the bone structure and muscles in children who have cleft palates may make it more difficult for the eustachian tube to drain.

Most ear infections don't cause long-term complications. Ear infections that happen again and again can lead to serious complications:

• Impaired hearing. Mild hearing loss that comes and goes is fairly common with an ear infection, but it usually gets better after the infection clears. Ear infections that happen again and again, or fluid in the middle ear, may lead to more-significant hearing loss. If there is some permanent damage to the eardrum or other middle ear structures, permanent hearing loss may occur.
• Speech or developmental delays. If hearing is temporarily or permanently impaired in infants and toddlers, they may experience delays in speech, social and developmental skills.
• Spread of infection. Untreated infections or infections that don't respond well to treatment can spread to nearby tissues. Infection of the mastoid, the bony protrusion behind the ear, is called mastoiditis. This infection can result in damage to the bone and the formation of pus-filled cysts. Rarely, serious middle ear infections spread to other tissues in the skull, including the brain or the membranes surrounding the brain (meningitis).
• Tearing of the eardrum. Most eardrum tears heal within 72 hours. In some cases, surgical repair is needed.