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 Malignant External Otitis Malignant external otitis, also referred to as skull base osteomyelitis or necrotizing otitis externa, is typically a Pseudomonas osteomyelitis of the temporal bone. Methicillin-resistant Staphylococcus... read more is a severe (usually Pseudomonas) osteomyelitis of the temporal bone, usually affecting older adults, diabetics, 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] in recent years).
Predisposing conditions include
Inadvertent injury to the canal caused by cleaning with cotton swabs or other objects
Decreased canal acidity (possibly due to the repeated presence of water)
Irritants (eg, hair spray, hair dye)
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. Sometimes, a foul-smelling discharge and hearing loss occur if the canal becomes swollen or filled with purulent debris. Exquisite tenderness accompanies traction of the pinna or pressure over the tragus. Otoscopic examination is painful and difficult to conduct. It shows the ear canal to be red, swollen, and littered with moist, purulent debris and desquamated epithelium.
Otomycosis is more pruritic than painful, and patients also complain of aural fullness. Otomycosis caused by A. niger usually manifests with grayish black or yellow dots (fungal conidiophores) surrounded by a cottonlike material (fungal hyphae). Infection caused by C. albicans does not show any visible fungi but usually contains 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
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 Otitis Media (Acute) Acute otitis media is a bacterial or viral infection of the middle ear, usually accompanying an upper respiratory infection. Symptoms include otalgia, often with systemic symptoms (eg, fever... read more 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
Topical acetic acid and corticosteroids
Sometimes topical antibiotics
In mild and 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.
Mild external otitis can be treated by altering the ear canal’s pH with 2% acetic acid (or white vinegar) and by relieving inflammation with topical hydrocortisone; these are given as 5 drops 3 times a day for 7 days.
Moderate external otitis requires the addition of an antibacterial solution or suspension, such as ciprofloxacin, ofloxacin, or neomycin/polymyxin, (the neomycin component is highly sensitizing and allergy is common). When inflammation of the ear canal is relatively severe, an ear wick should be placed into the ear canal and wetted with Burow solution (5% aluminum acetate) or a topical antibiotic 4 times a day. The wick helps direct the drops deeper into the external canal when the canal is greatly swollen. The wick is left in place for 24 to 72 hours (or may fall out on its own), after which time the swelling may have receded enough to allow the instillation of drops directly into the canal.
Severe external otitis or the presence of cellulitis extending beyond the ear canal may require systemic antibiotics, such as cephalexin 500 mg orally 4 times a day for 10 days or ciprofloxacin 500 mg orally 2 times a day for 10 days. 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 requires thorough cleaning of the ear canal and application of an antimycotic solution (eg, gentian violet, cresylate acetate, nystatin, clotrimazole, or even a combination of acetic acid and isopropyl alcohol). However, these solutions should not be used if the tympanic membrane is perforated, because they can cause severe pain or damage to the inner ear. Repeated cleanings and treatments may be needed to fully eradicate the infection.
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. Incision is of little value, however, if the patient is seen at an early stage. Topical antibiotics are ineffective; oral antistaphylococcal antibiotics should be given. Analgesics, such as oxycodone with acetaminophen, may be necessary for pain relief. Dry heat can also lessen pain and hasten resolution.
Pearls & Pitfalls
Prevention of Acute External Otitis
External otitis often can be prevented by applying a few drops of a 1:1 mixture of rubbing alcohol and white vinegar (as long as the eardrum is intact) immediately after swimming. The alcohol helps remove (evaporate) water, and the vinegar alters the pH of the canal. Use of cotton swabs or other implements in the canal should be strongly discouraged.
Acute external otitis is usually bacterial (pseudomonal); fungal causes are less likely and cause more itching and less pain.
Severe pain with pulling on the pinna 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 mild cases, apply acetic acid and hydrocortisone drops.
For more severe cases, debridement is critical along with topical antibiotics (use a wick if the canal is swollen); sometimes give systemic antibiotics.
Hajioff D, MacKeith S: Otitis externa. BMJ Clin Evid 0510, 2015.