Otitis externa

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).

When to call the doctor

The doctor should be called if any of the following symptoms are present:

• pain in an ear with or without fever
• persistent itching of the ear or in the ear canal
• loss of hearing or decreased hearing in one or both ears
• discharge from an ear, especially if it is thick, discolored, bloody, or foul-smelling

Diagnosis

Diagnosis of uncomplicated otitis externa is usually quite simple. The symptoms alone, of ear pain worsened by any touch to the outer ear, are characteristic of otitis externa. Examination of the ear canal will usually reveal redness and swelling. It may be impossible (due to pain and swelling) to see much of the ear canal, but this inability itself is diagnostic.

If there is a need to identify the types of organisms causing otitis externa, the canal can be gently swabbed to obtain a specimen. The organisms present in the specimen can then be cultured (allowed to multiply) in a laboratory, and then viewed under a microscope to allow identification of the causative organisms.

If the rare infection malignant otitis externa is suspected, computed tomography scan (CT scan) or magnetic resonance imaging (MRI) scans will be performed to determine how widely the infection has spread within bone and tissue. A swab of the external canal will not necessarily reveal the actual causative organism, so some other tissue sample (biopsy) will need to be obtained. The CT or MRI will help the doctor decide where the most severe focus of infection is located, in order to guide the choice of a biopsy site.

Treatment

Otitis externa us usually not a dangerous condition and often clears up by itself within a few days. To aid in the healing, the infected ear canal can be washed with an over-the-counter topical antiseptic. Pain can be relieved be placing a warm heating pad or compress on the infected ear as well as through the use of an over-thecounter pain reliever such as acetaminophen or aspirin. During the healing process, the infected ear canal must be kept dry, even while showering, through the use of ear plugs or a shower cap.

If the pain worsens or does not improve within 24 hours, or for the fastest way to relieve pain and to prevent the spread of infection, the doctor should be seen. The doctor will clean the ear with a suction-tipped probe or other type of suction device to relieve irritation and pain. Antibiotics will applied directly to the skin of the ear canal ( topical antibiotics ) to fight the infection. These antibiotics are often combined in a preparation that includes a steroid medication that reduces the itching, inflammation and swelling within the ear canal. For full treatment, eardrops are usually applied several times a day for seven to 10 days.

If the opening to the ear is narrowed by swelling, a cotton wick may be inserted into the ear canal to help carry the eardrops into the ear more effectively. The medications are applied directly to the wick, enough times per day to allow the wick to remain continuously saturated. After the wick is removed, usually after about 48 hours, the medications are then put directly into the ear canal three to four times each day.

For severe infection, oral antiobiotics may be prescribed. If the otitis externa infection is caused by the presence of a foreign body in the ear, the infection will not improve until the foreign body is removed.

In malignant otitis externa, antibiotics will almost always need to be given intravenously (IV). If the CT or MRI scan reveals that the infection has spread extensively, these IV antibiotics will need to be continued for six to eight weeks. If the infection is in an earlier stage, two weeks of IV antibiotics can be followed by six weeks of antibiotics by mouth.

Alternative treatment

Mullein ( Verbascum thapsus ) oil has anti-inflammatory properties and may be apppied to the infected ear canal (one to three drops every three hours) to help soothe and heal the ear. Garlic ( Allium sativum ) is a natural antibiotic. Garlic juice can be combined with equal parts of glycerin and a carrier oil such as olive or sweet olive and applied (one to three drops) to the infected ear every three hours.

Prognosis

The prognosis is excellent for otitis externa, for it is usually easily treated. Basic treatment measures will cure 90 percent of cases without complication. However, it may recur in certain susceptible individuals. Left untreated, malignant otitis externa may spread sufficiently to cause death.

Prevention

Swimming in polluted water and in pools or hot tubs without good chlorine and pH control should be avoided.

Keeping the ear dry is an important aspect of prevention of otitis externa. Before swimming, a protective coating consisting of several drops of mineral oil, baby oil, or lanolin can be applied to the ear canal. After swimming, several drops of a mixture of isopropyl alcohol and white vinegar can be put into the ear canal to ensure that it dries adequately. The head should be tilted so that the solution reaches the bottom of the ear canal; then the liquid should be drained out.

Care should be taken when cleaning ears. The outer ear should be cleaned wiped with a clean washcloth. The use of pointed objects to dig into the ear canal, especially those that can scratch the skin, should be avoided.

The most serious complications of malignant otitis externa can be avoided by careful attention to early symptoms of ear pain and drainage from the ear canal. Children with conditions that put them at higher risk for this infection (diabetes or conditions that weaken the immune system) should always report new symptoms immediately to the doctor.

Parental concerns

Parents should teach their children how to clean their ears without using sharp objects and to dry their ears thoroughly after swimming, showering, or bathing.

Resources

BOOKS

"External Otitis." In Nelson Textbook of Pediatrics , ed. Richard E. Behrman. Philadelphia: W. B. Saunders Co., 1996.

Friedman, Ellen M. My Ear Hurts! Fireside, 2001.

PERIODICALS

"Keep Your Ears Dry." Consumer Reports on Health , 7, no. 7 (July 1995): 80+.

Moss, Richard. "Swimmers Ear." Pediatrics for Parents 17, no. 4 (Apr. 1996): 3+.

ORGANIZATIONS

American Academy of Otolaryngology-Head and Neck Surgery, Inc. One Prince St., Alexandria VA 22314-3357. (703) 836-4444. Web site:http://www.entnet.

WEB SITES

"Healthy Swimming." National Center for Infectious Diseases, Centers for Disease Control and Prevention. http://cdc.gov/healthyswimming/swimmers_ear.htm.

Judith Sims