Brief Summary of Otitis externa

Also known as external otitis and swimmer’s ear, otitis externa is an inflammation of the skin of the external ear canal and auricle. It may be acute or chronic, and it’s most common in the summer. With treatment, acute otitis externa usually subsides within 7 days (although it may become chronic) and tends to recur.

Causes
Otitis externa usually results from bacterial infection with an organism, such as Pseudomonas, Proteus vulgaris, streptococci, or Staphylococcus aureus; sometimes it stems from a fungus, such as Aspergillus niger or Candida albicans (fungal otitis externa is most common in the tropics). Occasionally, chronic otitis externa results from dermatologic conditions, such as seborrhea or psoriasis. 

Predisposing factors include:

• swimming in contaminated water (cerumen creates a culture medium for the waterborne organism)
• cleaning the ear canal with a cotton swab, bobby pin, finger, or other foreign objects (irritates the ear canal and may introduce the infecting microorganism)
• exposure to dust, hair care products, or other irritants (causes the patient to scratch his ear, excoriating the auricle and canal)
• regular use of earphones, earplugs, or earmuffs (traps moisture in the ear canal, creating a culture medium for infection)
• chronic drainage from a perforated tympanic membrane.

Signs and symptoms
Acute otitis externa characteristically produces moderate to severe pain that’s exacerbated by manipulation of the auricle or tragus, clenching of the teeth, opening of the mouth, or chewing. Other signs and symptoms include fever, foul-smelling aural discharge, regional cellulitis, and partial hearing loss.

Fungal otitis externa may be asymptomatic, although A. niger produces a black or gray blotting paper–like growth in the ear canal. 

With chronic otitis externa, pruritus replaces pain, which may lead to scaling and skin thickening with a resultant narrowing of the lumen. An aural discharge may also occur. Asteatosis (lack of cerumen) is common.

Diagnosis
Physical examination confirms otitis externa. With acute otitis externa, otoscopy reveals a swollen external ear canal (sometimes to the point of complete closure), periauricular lymphadenopathy (tender nodes in front of the tragus, behind the ear, or in the upper neck) and, occasionally, regional cellulitis.
With fungal otitis externa, removal of growth shows thick red epithelium. Microscopic examination or culture and sensitivity tests can identify the causative organism and determine antibiotic treatment. Pain on palpation of the tragus or auricle distinguishes acute otitis externa from otitis media.
With chronic otitis externa, physical examination shows thick red epithelium in the ear canal. Severe chronic otitis externa may reflect underlying diabetes mellitus, hypothyroidism, or nephritis.

Treatment
Treatment varies, depending on the type of otitis externa.

Acute otitis externa

To relieve the pain of acute otitis externa, treatment includes heat therapy to the periauricular region (heat lamp; hot, damp compresses; heating pad), aspirin or acetaminophen, and codeine. Instillation of antibiotic eardrops (with or without hydrocortisone) follows cleaning of the ear and removal of debris. If fever persists or regional cellulitis develops, a systemic antibiotic is necessary.

Fungal otitis externa
As with other forms of this disorder, fungal otitis externa necessitates careful cleaning of the ear. Application of a keratolytic or 2% salicylic acid in cream containing nystatin may help treat otitis externa resulting from candidal organisms.
Instillation of slightly acidic eardrops creates an unfavorable environment in the ear canal for most fungi as well as Pseudomonas.

Chronic otitis externa
Primary treatment involves cleaning the ear and removing debris. Supplemental therapy includes instillation of antibiotic eardrops or application of antibiotic ointment or cream (neomycin, bacitracin, or polymyxin, possibly combined with hydrocortisone). Another ointment contains phenol, salicylic acid, precipitated sulfur, and petroleum jelly and produces exfoliative and antipruritic effects.
For mild chronic otitis externa, treatment may include instilling antibiotic eardrops once or twice weekly and wearing specially fitted earplugs while showering, shampooing, or swimming.

Special considerations
If the patient has acute otitis externa:

• Monitor vital signs, particularly temperature. Watch for and record the type and amount of aural drainage.
• Remove debris, gently clean the ear canal, and then dry gently but thoroughly. (With severe otitis externa, cleaning may be delayed until after initial treatment with antibiotic eardrops.)
• To instill eardrops in an adult, pull the pinna upward and backward to straighten the canal. For children, pull the pinna downward and backward. To ensure that the drops reach the epithelium, insert a wisp of cotton moistened with eardrops.

To prevent otitis externa:

• Suggest that the patient use custom-fitted earplugs to keep water out of his ears when showering, shampooing, or swimming.
• Warn the patient against putting any objects in his ears, such as cleaning the ears with cotton swabs or other objects.
• Urge prompt treatment of otitis media to prevent perforation of the tympanic membrane.
• If the patient is diabetic or immunocompromised, evaluate him for malignant otitis externa (drainage, hearing loss, ear pain, itching, fever). Appropriate treatments include antibiotics and surgical debridement.