Key Facts

Otitis externa is diffuse inflammation of the skin of the external auditory canal, with or without infection. It is extremely common, particularly in swimmers ('swimmer's ear'), and usually responds well to topical treatment.

Epidemiology

• Lifetime prevalence: 10%
• Accounts for 1% of GP consultations
• Peak incidence in summer months and tropical climates
• More common in swimmers, hearing aid users, and eczema sufferers
• Annual incidence: 10-20 per 1,000

Aetiology

• Bacterial (most common): Pseudomonas aeruginosa (60-70%), Staphylococcus aureus (10-20%), polymicrobial
• Fungal (otomycosis, 10%): Aspergillus niger (black spores), Candida albicans (white)
• Predisposing factors: excessive moisture (swimming), trauma (cotton buds, hearing aids), eczema/psoriasis, narrow ear canals, absence of cerumen, immunosuppression, diabetes
• Dermatological: eczema, psoriasis, contact dermatitis (nickel earrings, hearing aid material, topical antibiotic sensitivity)

Pathophysiology

• Normal protective cerumen barrier is disrupted (excessive cleaning, moisture)
• Loss of cerumen's acidic, hydrophobic, antimicrobial properties
• Canal skin becomes waterlogged, macerated, and susceptible to infection
• Bacterial colonisation triggers inflammatory response
• Oedema and debris accumulate, creating a warm, moist environment that perpetuates infection
• In malignant OE: Pseudomonas invades from canal skin into periosteum and temporal bone, causing osteomyelitis

Typical Presentation

• Ear pain (otalgia): often severe, worse on tragal pressure (tragal tenderness) and pinna manipulation
• Ear discharge: may be scanty or profuse, often offensive
• Itching (early symptom)
• Hearing loss (conductive, due to canal oedema and debris)
• Ear fullness

Examination Findings

• Erythematous, oedematous ear canal
• Debris, discharge, or crusting in canal
• Tragal tenderness (distinguishes from otitis media)
• Pinna manipulation painful
• TM may be obscured; if visible, usually normal (unless concurrent OE and OM)
• Pre- or post-auricular lymphadenopathy

Malignant (Necrotising) Otitis Externa

• Severe, unremitting ear pain (especially at night)
• Granulation tissue at bone-cartilage junction of EAC (pathognomonic)
• Cranial nerve palsies (VII most common, then IX, X, XI, XII)
• Diabetic or immunocompromised patient
• Systemically unwell

Red Flags

• Severe pain disproportionate to findings (malignant OE)
• Granulation tissue in EAC
• Cranial nerve palsy
• Diabetes/immunosuppression with worsening OE
• Not responding to 2 weeks of topical treatment
• Mastoid tenderness

Bedside

• Otoscopy: canal erythema, oedema, debris; TM often obscured but should be normal if visible
• Tragal tenderness testing
• Assessment of hearing
• Cranial nerve examination (if malignant OE suspected — especially VII)

Bloods

• Not required for uncomplicated OE
• FBC, CRP, ESR, HbA1c, blood cultures: if malignant OE suspected

Microbiology

• Ear swab: if not responding to empirical treatment or recurrent infection
• Fungal culture: if otomycosis suspected

Imaging

• CT temporal bone: if malignant OE suspected (bony erosion, skull base involvement)
• MRI: for soft tissue assessment and intracranial extension
• Technetium-99m bone scan or Gallium-67 scan: sensitive for osteomyelitis in malignant OE

Special Tests

• Biopsy of granulation tissue: to exclude malignancy (squamous cell carcinoma) and confirm diagnosis in malignant OE

Non-pharmacological

• Aural toilet: microsuction (gold standard) or dry mopping under direct vision
• Keep ear dry: use ear plugs or cotton wool with Vaseline when bathing/swimming
• Avoid cotton buds and ear instrumentation
• Pope wick insertion: if canal is too swollen for drops to penetrate (remove/replace in 48-72 hours)

Pharmacological

• First-line: topical antibiotic-steroid drops:
  • Ciprofloxacin 0.3%/dexamethasone 0.1% (Cilodex) 3 drops BD for 7 days
  • OR Sofradex (framycetin/gramicidin/dexamethasone) 3 drops TDS for 7 days
  • Avoid aminoglycoside drops (gentamicin, neomycin) if TM perforation (ototoxicity risk)
• Otomycosis: clotrimazole 1% drops/cream (antifungal), aural toilet; acetic acid 2% drops
• Second-line (not improving): ear swab and adjust antibiotics; consider acetic acid 2% spray (EarCalm)
• Analgesia: paracetamol, ibuprofen; codeine for severe pain
• Malignant otitis externa:
  • IV ciprofloxacin (400mg BD) or IV piperacillin-tazobactam (4.5g TDS) for 6-8 weeks
  • Prolonged course of oral ciprofloxacin 750mg BD following IV treatment

Surgical

• Surgical debridement: for malignant OE with extensive disease
• Rarely required for uncomplicated OE

Referral Criteria

• ENT referral: suspected malignant OE, not responding to 2 weeks of treatment, recurrent OE (>4 episodes/year), suspected cholesteatoma or canal malignancy
• Urgent ENT referral: cranial nerve palsy, granulation tissue, severe pain in diabetic patient
• Audiology referral if persistent hearing loss

• Uncomplicated OE: >95% resolve with topical treatment within 7-10 days
• Recurrence rate: 30-40% (particularly in swimmers, hearing aid users, eczema)
• Otomycosis: may require prolonged treatment (2-4 weeks) and has higher recurrence rate
• Malignant OE: mortality 10-20% (historically higher, improving with modern antibiotics)
  • Cranial nerve involvement indicates worse prognosis
  • Skull base osteomyelitis may require months of antibiotics
• Chronic OE may develop in 5-10% — requires ongoing management and triggers avoidance

Comparison: Otitis Externa vs Otitis Media

Topical Ear Drop Selection