Otitis Externa
Otitis externa, also known as swimmer’s ear and tropical ear, is inflammation of the external auditory canal and may also involve the pinna or tympanic membrane. Acute otitis externa is usually bacterial, while chronic otitis externa is more often associated with fungal infection or underlying skin disease. Malignant otitis externa is a severe necrotising infection that can spread to the temporal bone and requires urgent specialist assessment.
This updated UKMLA guide to otitis externa (acute, chronic and malignant) is based on NICE CKS, which covers causes, risk factors, symptoms, complications, diagnosis and management.
Classification
| Acute otitis externa | Duration of <6 weeks |
| Chronic otitis externa | Duration of >3 months |
| Malignant (necrotising) otitis externa | Potentially life-threatening progressive infection of the external ear canal, which may spread to cause osteomyelitis of the temporal bone and adjacent structures |
Causes and Risk Factors
| Acute otitis externa | Typically caused by bacterial infection
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| Chronic otitis externa | More likely to be caused by fungal infection (but not exclusively):
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| Malignant (necrotising) otitis externa | Commonly caused by Pseudomonas aeruginosa infection |
Risk Factors
Unlike in otitis media (which is more common in young children), otitis externa is common in all age groups.
| Acute otitis externa | Acute otitis media (purulent middle ear secretions may enter the ear canal if the tympanic membrane is perforated)
Environmental exposures:
Concurrent skin conditions:
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| Chronic otitis externa |
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| Malignant (necrotising) otitis externa |
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Clinical Features
Acute Otitis Externa
Rapid onset of:
| Symptoms |
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| Signs |
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Less common features:
- Hearing loss
- Tender regional lymphadenopathy
Chronic Otitis Externa
The following lasting >3 months:
| Symptoms |
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| Signs |
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The presence of fluffy / cotton-like debris / hyphae / black debris in the ear canal is more suggestive of fungal infection – which is more common in chronic otitis externa.
The presence of purulent discharge makes bacterial infection more likely – which is more common in acute otitis externa.
Malignant Otitis Externa
| Symptoms |
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| Signs |
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Complications
Mainly complications of acute otitis externa:
- Progression into chronic otitis externa
- Regional spread of infection
- Perichondritis (erythema and swelling of the pinna that spares the ear lobe – may progress into sepsis and ear deformities)
- Pinna cellulitis (erythema and swelling of the pinna and ear lobe)
- Abscess formation
- Parotitis
- Myringitis (tympanic membrane inflammation) and tympanic membrane perforation
Chronic otitis externa can result in:
- Ear canal fibrosis and stenosis
- Tympanic membrane fibrosis with potential conductive hearing loss
Investigation and Diagnosis
Otitis externa is primarily a clinical diagnosis
Only consider ear swabs for microbiology if there is:
- Treatment failure
- Severe / recurrent / chronic otitis externa
- Ear canal occlusion (due to swelling and debris) causing difficulty in applying topical treatments
- Suspected spread of infection beyond the external auditory canal
Suspected malignant otitis externa usually warrants immediate specialist assessment.
Imaging is typically necessary to assess the extent of the disease: [Ref]
- 1st line: CT temporal bone
- Other: nuclear bone scans, MRI
Management
Acute and Chronic Otitis Externa
Conservative / General Management
| Patient education | Keep the ears clean and dry
Do not use cotton buds or other objects to clear the ear canal (to avoid trauma to the external ear canal) |
| Self-management | Paracetamol or ibuprofen for pain
Consider acetic acid 2% ear drops / spray (if ≥12 y/o) for a maximum of 7 days
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It is also important to manage any underlying causes or risk factors, including associated skin conditions
Antimicrobial Therapy
The choice of antimicrobial therapy depends on what is the more likely underlying cause:
- Purulent otorrhoea → likely bacterial infection (mainly in acute otitis externa)
- Fluffy / cotton-like debris / hyphae / black debris in the ear canal → likely fungal infection (mainly in chronic otitis externa)
Bacterial Infection Likely
1st line: consider 7-14 days of topical therapy
- Topical antibiotic (gentamicin / ciprofloxacin)
- Do NOT give gentamicin if the tympanic membrane is perforated, as it is ototoxic
- +/- Topical steroid (prednisolone or betamethasone) – especially if there is significant ear canal inflammation / oedema
Consider cleaning the external auditory canal (‘aural toilet’) before applying topical treatments to allow effective administration. Options include:
- Dry swabbing of secretions
- Ear irrigation to remove debris, earwax, and exudate (only if the tympanic membrane is intact and the person is not immunocompromised)
Consider oral antibiotics if:
- Patient is immunocompromised, or
- Presence of severe infection, or
- Spread beyond the external ear canal (e.g. cervical lymphadenopathy, periauricular cellulitis, skull base osteomyelitis)
Choice of oral antibiotics:
- If Pseudomonas is suspected → ciprofloxacin or aminoglycoside
- Otherwise → flucloxacillin (if penicillin allergy: clarithromycin / azithromycin / erythromycin)
Fungal Infection Likely
Consider:
- Topical antifungal (e.g. clotrimazole)
- +/- Topical steroid (prednisolone or betamethasone)
No Obvious Bacterial or Fungal Infection
Consider a topical steroid (prednisolone or betamethasone)
If symptoms persist, consider a trial of topical antifungal
Malignant (Necrotising) Otitis Externa
Suspected malignant otitis externa usually warrants immediate specialist assessment and management.
Key management principles: [Ref1][Ref2]
- Topical AND systemic anti-pseudomonal antibiotics (e.g. ciprofloxacin)
- Surgical management (mastoidectomy) may be necessary if
- No improvement after 6 weeks
- Facial nerve involvement
- Aggressive disease
References