What Causes an Ear Infection?

An ear infection is often the result of bacteria or fungi causing infection in any of the three parts that make up your ear.

A virus may also be identified as the pathogen creating the conditions necessary for a bacterial infection to develop. The three parts of your ear include the outer ear, the middle ear and the inner ear.

Your outer ear includes the pinna (visible outer ear) and the canal (called the external auditory canal) that leads to the eardrum (tympanic membrane).

Your middle ear is behind the eardrum and contains three tiny bones (the ossicles: the malleus, incus and stapes) that amplify sound.

Your inner ear is where sounds are translated to electrical impulses by the cochlea and sent to the brain.

There are many causes of ear infection. Some of the contributing conditions and scenarios include:

  • upper respiratory tract infections (a cold for example)
  • trauma or injury to the ear (including light scratches)
  • Eustachian tube dysfunction
  • eczema or other chronic skin conditions
  • a lack of earwax which helps ears stay dry and has antifungal and antibacterial properties
  • swimming in polluted waters
  • not drying the outer ear properly after getting wet
  • excessive cleaning of the ears with cotton buds or other foreign objects

10 Signs of an Ear Infection

The symptoms of an ear infection depend on the type of infection and where it occurs in the ear. 

  1. Earache.
  2. Mild deafness.
  3.  Ear discharge.
  4. Fever.
  5. Headache.
  6. Loss of appetite.
  7. Ears are itchy.
  8. Blisters inside or outside of the ear.
  9. Hearing ringing, buzzing or humming.
  10. Vertigo or loss of balance.

6 Types of Ear Infection

There are many types of ear infection with many different causes. Most are caused by a bacterial or fungal infection. In some cases, a virus will be identified as the pathogen causing infection. The following ear infections are some that you might come across.

Otitis Media

Otitis media is a nonexclusive term used to describe many middle ear infections. Otitis media is often caused by a respiratory illness such as a cold, flu or allergy with swelling and fluid accumulation in the middle ear. Eustachian tube dysfunction that traps fluid in the middle ear is common to most types of otitis media.

The more prevalent middle ear infections include:

  • acute otitis media
  • otitis media with effusion
  • chronic suppurative otitis media
  • adhesive otitis media

Otitis media is more common in babies and young children due to the size and relative position of the Eustachian tube. Otitis media is the leading condition for antibiotic prescribing and surgery in young children.

Children with otitis media will usually have symptoms related to:

  • fever and/or pain (acute otitis media)
  • difficulty hearing (otitis media with effusion)
  • ear discharge (acute otitis media with perforation or chronic suppurative otitis media)
Bulging Tympanic Membrane typical of Acute Otitis Media
Bulging Tympanic Membrane

Acute otitis media (AOM) is a bacterial or viral infection of the middle ear that progresses rapidly. It is a common problem in early childhood. The middle ear will show signs and symptoms of acute inflammation and effusion, usually within 48 hours after symptoms begin.

The symptoms of otitis media are earache, discharge from the ear, ear-popping, ear fullness, hearing loss, fever and dizziness.

A baby or young child who has AOM may tug on the ear, cry or fuss more than usual, lose his or her appetite, and have trouble sleeping.

Visible with a microscope, a bulging tympanic membrane is typical in a case of AOM.


Otitis media with effusion (OME), also called glue ear, is characterised by fluid in the middle ear without signs or symptoms of inflammation. OME can occur just prior to or persist after infection for a few days or up to many weeks. Children are more likely to experience OME due to the small size and shape of their Eustachian tube relative to adults.

75% of children have at least one OME episode by school age. Most often between the ages of 6 months to 4 years.

OME isn’t an ear infection, but they can be related. For example, an ear infection can affect how well fluid flows through the middle ear. Your ear may retain fluid even after an ear infection is resolved. A blocked Eustachian tube and excess fluid provide the ideal environment for bacteria to flourish. Flourishing bacteria may then lead to an ear infection.

Otitis externa
Otitis externa

Otitis externa, also called swimmers ear is an infection of the outer ear. Often the result of water getting trapped in your ear, followed by the growth of bacteria or fungal organisms. It commonly occurs during the summer months when people swim more frequently and their ears stay warm and moist.

Possible causes of otitis externa may include:

  • swimming in water that contains bacteria
  • scratching the inside of your ear
  • getting something stuck in your ear

Otitis externa is also more common in tropical environments, where it is often more difficult to keep your outer ear dry.

The usual signs that you may have otitis externa are itchiness in the ear, hearing loss, ear pain, and having yellow or yellow-green, smelly pus drain from the ear.

This type of ear infection is typically treated with antibiotic ear drops. The ears should also be kept dry during the treatment of this ear infection. Microsuction may help to clear the ear canal, making it easier to administer ear drops, soothe the irritation and relieve the blocked feeling.

Otomycosis - fungal infection of the outer ear

Otomycosis is a fungal infection of the outer ear. Most infections are caused by Aspergillus species or, less commonly, Candida. Typically this type of infection will cause dry skin, inflammation, and a smelly discharge in the ear canal.

Fungi are present in our daily environments and usually pose no threat. However, people with a weakened immune system are more susceptible to infection. As are those who live in warmer tropical environments where fungi tend to thrive.

The risk factors for otomycosis are quite similar to those of otitis externa. Certain activities and injuries can make you more prone to otomycosis, such as:

  • swimming or surfing, especially in contaminated water
  • an injury or scratch in your ear canal
  • excessive cleaning 
  • a lack of ear wax protecting your ears
  • eczema and other skin conditions
Otomycosis is usually easily treated with topical antifungal dops and creams. Oral medications may be used for more severe infections or for species of fungi that are resistant to topical medications.
Mastoiditis occurs in the temporal bone of your skull
Mastoiditis in the temporal bone

Mastoiditis is more common in children, but it can affect adults as well. It is caused by a middle ear infection that has been left untreated. The infection can spread from your middle ear, invading the mastoid air cells in the temporal bone of your skull.

Symptoms include swelling, tenderness and redness around the temporal bone. Fever, ear pain and discharge are also possible.

Many vital structures pass through the mastoid, so if an infection spreads outside of the mastoid bone serious complications can occur. The infection cannot be treated at home and should always be assessed by a health care professional.

This page was written by Jerika Pring, Registered Nurse at Ear Health on:

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