Otitis Externa Health Article

Definition

Otitis externa refers to an infection of the ear canal (outer ear), the tube leading from the outside opening of the ear in towards the ear drum. The infection usually develops in children and adolescents whose ears are exposed to persistent, excessive moisture.

Description

The external ear canal is a tube approximately 1 in (2.5 cm) in length that runs from the outside opening of the ear to the start of the middle ear, which is behind the tympanic membrane (ear drum). The canal is partly cartilage and partly bone. The lining of the ear canal is skin, which is attached directly to the covering of the bone. Glands within the skin of the canal produce a waxy substance called cerumen (popularly called earwax). Cerumen is designed to protect the ear canal, repel water, and keep the ear canal too acidic to allow bacteria to grow.

Continually exposing the ear canal to moisture may cause significant loss of cerumen. The delicate skin of the ear canal, unprotected by cerumen, retains moisture and becomes irritated. Without cerumen, the ear canal stops being appropriately acidic, which allows for the growth of microorganisms. Thus, the warm, moist, dark environment of the ear canal becomes a hospitable environment for development of an infection.

Otitis externa is commonly referred to as swimmer's ear.

Demographics

Although all age groups are affected by otitis externa, children, adolescents, and young adults whose ears are exposed to persistent, excessive moisture develop the infection most often. Otitis externa occurs most often in warm climates and during the summer months, when more people are participating in water activities. The ratio of occurrence in males is equal to that of females. People in some racial groups have a smaller size of the ear canal, which may predispose them to infection.

Causes and symptoms

Chidren and adolescents with otitis externa often have been diving or swimming for long periods of time, especially in polluted lakes, rivers, or ponds. Routine showering can also lead to otitis externa. Water in the ear canal can carry infectious microorganisms into the ear canal.

Bacteria, fungi, and viruses have all been implicated in causing otitis externa. However, most commonly otitis externa is caused by bacteria, especially Pseudomonas aeruginosa. Other bacteria that can cause otitis externa include Enterobacter aerogenes, Proteus mirabilis, Klebsiella pneumoniae, Staphylococcus epidermidis, and bacteria of the family called Streptococci. Occasionally, fungi may cause otitis externa. These include Candida and Aspergillus. Two types of viruses, called herpesvirus hominis and varicella-zoster virus, have also been identified as causing otitis externa.

Other conditions predisposing to otitis externa include the use of cotton swabs to clean the ear canals. This pushes cerumen and normal skin debris back into the ear canal, instead of allowing the ear canal's normal cleaning mechanism of the ear to work, which would ordinarily move accumulations of cerumen and debris out of the ear. Also, putting other items into the ear can scratch the canal, making it more susceptible to infection. For example, children may insert a foreign body in their ear canal and not mention it to their parents. Hair spray or hair coloring, which can irritate the ear canal, may also lead to otitis externa. A hearing aid can trap moisture in the ear canal and should be taken out as often as possible to allow the ear an opportunity to dry out.

The first symptom of otitis externa is often itching of the ear canal, followed by watery discharge from the ear. Eventually, the ear begins to feel extremely painful. Any touch, movement, or pressure on the outside structure of the ear may cause severe pain. If the canal is excessively swollen, hearing may become muffled. The canal may appear swollen and red, and there may be evidence of foul-smelling, greenish-yellow pus.

In severe cases, otitis externa may be accompanied by fever. Often, this indicates that the outside ear structure has become infected as well. It will become red and swollen, and there may be enlarged and tender lymph nodes in front of, or behind, the ear.

A serious and life-threatening type of otitis externa is called malignant otitis externa. This is an infection that most commonly affects persons who have diabetes or in persons with weakened immune systems. In malignant otitis externa, a patient has usually had minor symptoms of otitis externa for some months, with pain and drainage. The causative bacteria is usually Pseudomonas aeruginosa. This bacteria spreads from the external canal into all of the nearby tissues, including the bones of the skull. Swelling and destruction of these tissues may lead to damage of certain nerves, resulting in spasms of the jaw muscles or paralysis of the facial muscles. Other, more severe, complications of this destructive infection include meningitis (swelling and infection of the coverings of the spinal cord and brain), brain infection, or brain abscess (the development of a pocket of infection with pus).