Otitis externa (OE) is an inflammation of the external auditory canal (EAC), which is most often the result of a local bacterial infection. Risk factors for OE include exposure to water and injury to the skin of the EAC. OE is primarily a clinical diagnosis. It is characterized by ear pain, fullness, and/or itching, and tenderness of the tragus and/or pinna; otoscopy may show erythema, edema, debris, and/or otorrhea of the EAC. Treatment typically involves analgesia, keeping the EAC dry, and administering antiseptic, antibiotic, or glucocorticoid ear drops. Systemic antibiotic therapy is indicated in select cases, e.g., patients with immunosuppression and/or diabetes who are at risk of a more severe variant, malignant otitis externa. Malignant otitis externa is commonly caused by Pseudomonas aeruginosa, typically manifests with severe ear pain, and may lead to osteomyelitis of the skull base and subsequent complications such as cranial neuropathies. Immediate referral, diagnosis, and treatment with systemic antipseudomonal antibiotics are necessary.
Acute otitis externa 
- Bacterial infections (most common cause of otitis externa)
- Viral infections (rare): Herpes zoster, influenza viruses
- Fungal infections (less common): Aspergillus (accounts for 90% of all fungal otitis externa), Candida
- Noninfectious causes (less common)
- Risk factors
- Severe ear pain, particularly at night
- Intense itching in the EAC
- Hearing loss
- Jaw pain 
Examination findings 
- Tenderness on palpation of the tragus
- Pulling up and back on the auricle causes pain.
- The following may also be present:
- Erythematous and edematous EAC
- Otorrhea or debris
- EAC may be occluded by a furuncle, impacted cerumen, or foreign body
- The tympanic membrane may be erythematous but should not bulge.
Subtypes and variants
Malignant otitis externa (necrotizing otitis externa) 
- Risk factors for MOE
Clinical features of MOE 
- Severe, persistent ear pain and/or jaw pain 
- Symptoms of extension of infection, e.g.:
- Conductive hearing loss
- Red and swollen; EAC and periauricular soft tissue 
- Otoscopic findings: granulation tissue at the cartilage-bone junction of the EAC 
Diagnostics of MOE 
All patients require laboratory studies and imaging.
- Laboratory studies 
Imaging: More than one modality is often required. 
- Modalities 
- Surgical biopsy: Consider if there is diagnostic uncertainty or insufficient response to treatment. 
Systemic antibiotic therapy: typically lasting for 6–8 weeks ; 
- Initial empiric therapy: Use two antipseudomonal agents from different classes for ≥ 2 weeks, e.g., ciprofloxacin PLUS one of the following:
- Once culture results are available, tailor antibiotics to sensitivities and continue for an additional 4–6 weeks.
- Local treatment 
- Surgery: may be required in select cases, e.g., abscess drainage or debridement of
- Monitoring of treatment response
- Osteomyelitis of the skull base manifesting with:
- Relapse in up to 20% of patients 
- Overall mortality: < 10%
- Rates may be higher in patients aged over 80 years or with significant comorbidities.
Localized otitis externa (furunculosis) 
- Local application of heat
- Incision and drainage
- Systemic antibiotics (see “Empiric antibiotic therapy for skin and soft tissue infections”)
Otomycosis (fungal otitis externa) 
- Risk factors
- Largely a clinical diagnosis; in addition to classic , patients may additionally have:
- Fungal culture is recommended. 
General principles 
- Diagnosis is clinical; AOE is likely if all of the following are present : 
- Diagnostic studies are only performed:
- In suspected comorbid disease
- To rule out
- For refractory disease or suspected subtypes, e.g., MOE
Diagnostic studies 
- Pneumatic otoscopy and/or tympanometry
- Screening for comorbidities: Consider based on clinical features.
- Culture of ear secretions should be obtained if there is: 
- Patients with : Laboratory studies and imaging are required (see “Diagnostics of MOE”).
|Differential diagnosis of otitis externa |
|Herpes zoster oticus|
|Temporomandibular joint (TMJ) syndrome|
The differential diagnoses listed here are not exhaustive.
The following applies to diffuse AOE. For the treatment of localized OE, otomycosis, and MOE, see “Subtypes and Variants.” COE is treated according to its etiology, e.g., fungal, allergic, or autoimmune. 
- Initiate supportive therapy as needed, e.g., analgesia, ear wick, aural toilet.
- Evaluate for indications for and start if present.
- For uncomplicated AOE, initiate . 
- Reassess at 48–72 hours; if there is no improvement, consider: 
- Consider a referral to otolaryngology in severe or refractory AOE.
Supportive therapy 
- Start scheduled oral analgesia. 
- Advise patients:
- Consider performing aural toilet or placing an ear wick to facilitate better topical treatment.
Systemic antibiotics for OE 
- Choice of agent: should cover P. aeruginosa and S. aureus, e.g., ciprofloxacin 
Choice of agent
- Multiple options are effective; choose based on patient factors, preference, cost, etc.
- Glucocorticoids (included in some preparations) may speed up symptom improvement.
Treatment duration 
- Typically 7 days; may be extended up to 10–14 days if needed
- Patients with persistent symptoms at 14 days should be reassessed.
|Topical antimicrobial therapy for acute otitis externa |
- Recurrent episodes of OE
- Chronic dermatological conditions (e.g., atopic dermatitis, psoriasis)
- Frequent participation in water sports
- Avoid manipulation of the ear canal (e.g., use of cotton buds to clean the ear).
- Regularly remove and clean earrings and in-ear devices, e.g., hearing aids.
- Treat underlying chronic dermatological conditions.
- Frequent swimmers: Use a tight-fitting bathing cap or ear plugs. 
- After bathing or swimming:
- Tilt the head to remove water.
- Dry the ear with a blow-dryer at the lowest heat setting.
- Consider prophylactic use of acetic acid ear drops.