External otitis is an acute infection of the ear canal skin typically caused by bacteria; Pseudomonas
External otitis may manifest as a localized furuncle or as a diffuse infection of the entire canal (acute diffuse external otitis). The latter is often called swimmer’s ear; the combination of water in the canal and use of cotton swabs is the major risk factor. Malignant external otitis is a severe (usually due to Pseudomonas)osteomyelitis of the temporal bone, usually affecting older adults, patients with diabetes, and immunocompromised patients.
Etiology of Acute External Otitis
Acute diffuse external otitis is usually caused by bacteria, such as Pseudomonas aeruginosa, Proteus vulgaris, Staphylococcus aureus, or Escherichia coli. Fungal external otitis (otomycosis), typically caused by Aspergillus niger or Candida albicans, is less common. Furuncles usually are caused by S. aureus and by methicillin-resistant S. aureus (MRSA).
Predisposing conditions include
Inadvertent injury to the canal caused by cleaning with cotton swabs or other objects
Allergies
Decreased canal acidity (possibly due to the repeated presence of water)
Irritants (eg, hair spray, hair dye)
Use of earplugs or hearing aids (particularly if these devices are not adequately cleaned or do not fit correctly)
Attempts to clean the ear canal with cotton swabs can cause microabrasions of the delicate skin of the ear canal (these microabrasions act as portals of entry for bacteria) and may push debris and cerumen deeper into the canal. These accumulated substances tend to trap water, resulting in skin maceration that sets the stage for bacterial infection.
Symptoms and Signs of Acute External Otitis
Patients with external otitis have pain and drainage. If the canal becomes swollen or filled with purulent debris, patients sometimes have a foul-smelling discharge and hearing loss. Exquisite tenderness accompanies traction of the pinna or pressure over the tragus. Otoscopic examination is painful and difficult to conduct. The ear canal appears erythematous, swollen, and littered with moist, purulent debris and desquamated epithelium.
Otomycosis is more pruritic than painful, and patients also report aural fullness. Otomycosis caused by A. niger usually manifests with grayish black or yellow dots (fungal conidiophores) surrounded by a cottonlike material (fungal hyphae). In patients with infection caused by C. albicans, fungi are not visible, but usually, there is a thickened, creamy white exudate, which can be accompanied by spores that have a velvety appearance.
Furuncles cause severe pain and may drain sanguineous, purulent material. They appear as a focal, erythematous swelling (pimple).
Diagnosis of Acute External Otitis
Clinical evaluation
Diagnosis of external otitis is based on inspection. When discharge is copious, external otitis can be difficult to differentiate from an acute, purulent otitis media with tympanic membrane perforation; pain elicited by pulling on the pinna may indicate an external otitis. Fungal infection is diagnosed by appearance or culture.
Treatment of Acute External Otitis
Debridement
Sometimes topical antibiotics
(See also Clinical Practice Guideline: Acute Otitis Externa.)
In mild or moderate acute external otitis, topical antibiotics and corticosteroids are effective. First, the infected debris should be gently and thoroughly removed from the canal with suction or dry cotton swabs under adequate lighting. Water irrigation of the canal is contraindicated.
Neomycin/polymyxin
Severe external otitis or the presence of cellulitis1). An analgesic, such as a nonsteroidal anti-inflammatory drug or even an oral opioid, may be necessary for the first 24 to 48 hours.
Fungal external otitis
Dry ear precautions (eg, wearing shower cap, avoiding swimming) are strongly advised for both external otitis and fungal external otitis. A blow dryer on a low setting can also be used to reduce the humidity and moisture in the canal.
A furuncle, if obviously pointing, should be incised and drained. However, if the patient is seen at an early stage, incision is of little value. Topical antibiotics are ineffective; oral antistaphylococcal antibiotics should be given. Analgesics may be necessary for pain relief. Dry heat can also lessen pain and hasten resolution.
Pearls & Pitfalls
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Treatment reference
1. Jackson MA, Schutze GE: The use of systemic and topical fluoroquinolones. Pediatrics 138 (5):e20162706 2016. doi: 10.1542/peds.2016-2706
Prevention of Acute External Otitis
Key Points
Acute external otitis is usually bacterial (pseudomonal); fungal infections are less common and cause more itching and less pain.
Severe pain when the pinna is pulled suggests acute external otitis.
Under close and direct visualization, gently remove infected debris from the canal with suction or dry cotton swabs.
Do not irrigate the ear.
For moderate or severe cases, debridement and topical antibiotics (use a wick if the canal is swollen) are critical; sometimes give systemic antibiotics.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Hajioff D, MacKeith S: Otitis externa. BMJ Clin Evid 0510, 2015.
