Otitis externa is an inflammation or infection of the external auditory canal and/or auricle.1, 2, 3 This condition is one of the most common medical conditions that affect aquatic athletes. Individuals with allergic conditions, such as eczema, allergic rhinitis, or asthma, also have a significantly higher risk of developing this condition.4, 5 (See also the eMedicine articles Otitis Externa [in the Emergency Medicine section], Otitis Externa and Allergic Rhinitis [in the Pediatrics section], Allergic and Environmental Asthma [in the Allergy and Immunology section], and Allergic Rhinitis [in the Otolaryngology and Facial Plastic Surgery section], as well as Guidelines Issued for Acute Otitis Externa and Hyperbaric Oxygen as an Adjuvant Treatment for Malignant Otitis Externa on Medscape.)
Several factors can contribute to the development of otitis externa. Absence of cerumen, high humidity, increased temperature, and local trauma (eg, use of cotton swabs or hearing aids) can result in infection of the canal.6 Aquatic athletes are particularly prone to the development of otitis externa because repeated exposure to water results in removal of cerumen and drying of the external auditory canal. Otitis externa occurs more often in the summer months when swimming is more common,6, 7 and this condition is also common in tropical areas.8 The most common bacterial causes of otitis externa are Pseudomonas aeruginosa and Staphylococcus aureus.9
Otitis externa can be classified as follows:
Acute diffuse otitis externa is the most common form of otitis externa and is most commonly seen in swimmers. Acute diffuse otitis externa is usually caused by bacteria, but it can be occasionally caused by a fungus. Elements of acute diffuse otitis externa include rapid onset (generally within 48 h); symptoms of ear canal inflammation that include otalgia, itching, or fullness, with or without hearing loss or jaw pain; and tenderness of the tragus or pinna, or diffuse ear edema or erythema or both, with or without otorrhea, regional lymphadenitis, tympanic membrane erythema, or cellulitis of the pinna.8
Acute localized otitis externa, also known as furunculosis, is associated with infection of a hair follicle.
Chronic otitis externa is the same as acute diffuse otitis externa, but it is of longer duration (>6 wk).
Eczematous otitis externa encompasses various dermatologic conditions (eg, atopic dermatitis, psoriasis, lupus erythematosus, eczema) that may infect the external auditory canal and cause otitis externa. (See also the eMedicine articles Atopic Dermatitis [in the Dermatology section], Atopic Dermatitis [in the Pediatrics section], Psoriasis and Systemic Lupus Erythematosus [in the Emergency Medicine section], and Systemic Lupus Erythematosus [in the Rheumatology section].)
Necrotizing “malignant” otitis externa is an infection that extends into the deeper tissues adjacent to the auditory canal. This type of otitis externa primarily occurs in adult patients who are immunocompromised (eg, diabetes mellitus, acquired immunodeficiency syndrome [AIDS]) and is rarely described in children. Necrotizing otitis externa may result in cases of cellulitis and osteomyelitis. (See also the eMedicine articles External Ear, Malignant External Otitis [in the Otolaryngology and Facial Plastic Surgery section], Cellulitis [in the Dermatology section], Cellulitis [in the Infectious Diseases section], Cellulitis and Osteomyelitis [in the Emergency Medicine section], and Osteomyelitis, Chronic [in the Radiology section].)
For excellent patient education resources, visit eMedicine’s Ear, Nose, and Throat Center. Also, see eMedicine’s patient education article Swimmer’s Ear.
The external auditory canal is lined with squamous epithelium and is approximately 2.5 cm in length in adults. The function of the external auditory canal is to transmit sound to the middle ear while protecting more proximal structures from foreign bodies and any changes in environmental conditions. The outer one third of the canal is primarily cartilaginous and is oriented superiorly and posteriorly; this portion of the canal contains cerumen-producing apocrine glands. The inner two thirds of the canal is osseous, covered with thin skin that is tightly adhered, and oriented inferiorly and anteriorly; this portion of the canal is devoid of any apocrine glands or hair follicles.
The quantity of cerumen that is produced varies widely among individuals. Cerumen is generally acidic (pH 4-5), thus inhibiting bacterial or fungal growth. The waxy nature of the cerumen protects the underlying epithelium from maceration or skin breakdown.
Otitis externa likely develops in aquatic athletes or swimmers as a result of excessive water exposure that results in an overall reduction in cerumen. This reduction in cerumen can then lead to drying of the external auditory canal and pruritus. The pruritus can then lead to probing of the external auditory canal, resulting in skin breakdown and an entry site for infection. Obstruction of the external auditory canal by excessive cerumen, debris, surfer’s exostosis, or a narrow and tortuous canal may also lead to infection by means of moisture retention.
The most common offending organisms are P aeruginosa (50%), S aureus (23%), anaerobes and gram-negative organisms (12.5%), and fungi such as the Aspergillus and Candida species (12.5%). Otomycosis is an infection in the external auditory canal that is caused by the Aspergillus species 80-90% of the time. This condition is characterized by many long, white, filamentous hyphae that grow from the skin surface.
In one study, 91% of cases of external otitis were caused by bacteria.9 Elsewhere, up to 40% of cases of external otitis have no primary identifiable microorganism as a causative agent.
Annually, otitis externa occurs in 4 of every 1000 persons.4, 6 The incidence is higher during the summer months, presumably because participation in aquatic activities is higher.6, 7 Acute, chronic, and eczematous otitis externa are also common. Necrotizing otitis externa is rare.
The international frequency of otitis externa is unknown; however, the incidence is increased in tropical countries.8
The morbidity is low in aquatic athletes with acute diffuse otitis externa. However, in the event of the development of necrotizing otitis externa, there is a 20% mortality rate among adults, generally due to the associated comorbidities and the rapid extension of the infection to include sepsis or intracranial extension.
No racial predilection is reported for otitis externa.
No sex predilection has been described for otitis externa.
Generally, no association between the development of otitis externa and age exists. A single epidemiologic study in the United Kingdom found a similar 12-month prevalence for individuals aged 5-64 years and a slight increase in the prevalence for those older than 65 years.7 This was postulated to occur secondary to an increase in comorbidities, as well as an increase in the use of hearing aids, which may cause trauma to the external auditory canal.
The patient may report the following symptoms:
Discharge (Initially, the discharge may be clear and odorless, but it quickly becomes a purulent, foul-smelling discharge.)
Bilateral symptoms (rare)
Findings of the physical examination may include the following:
Tragal tenderness with manipulation
Erythematous and edematous external auditory canal
Eczema of auricle
Periauricular and cervical adenopathy
In severe cases, the infection may spread to the surrounding soft tissues, including the parotid gland. Bony extension may also occur into the mastoid bone, temporomandibular joint, and base of the skull, in which case cranial nerves VII (facial), IX (glossopharyngeal), X (vagus), XI (accessory), or XII (hypoglossal) may be affected.
The causes of otitis externa can be categorized as (1) obstructive (eg, cerumen, surfer’s exostosis, narrow or tortuous canal), resulting in water retention; (2) absence of cerumen, which may occur as a result of repeated water exposure; (3) trauma; and (4) an alteration of the pH of the canal.
Previous episodes of otitis externa
Swimming, diving, or participating in aquatic activities
Use of earplugs or probing of the external auditory canal (possibly secondary to trauma caused to the external auditory canal)
Hot, humid weather
Use of a hearing aid
Coexistence of eczema, allergic rhinitis, or asthma
Comorbidities such as diabetes mellitus, AIDS, leukopenia, or malnutrition