What causes recurrent otitis externa?

Causes of Recurrent Otitis Externa

Recurrent otitis externa is primarily caused by disruption of the ear canal's natural protective barriers, most commonly due to excessive moisture exposure, trauma to the ear canal, and underlying dermatologic conditions that compromise the skin integrity of the external auditory canal. 1, 2

Primary Causes

1. Moisture-Related Factors

• Humidity or prolonged water exposure 1
  • Swimming (hence the term "swimmer's ear") 3
  • Excessive sweating
  • High environmental humidity
  • Inadequate drying after water exposure

2. Trauma to the Ear Canal

• Self-inflicted trauma 4
  • Cotton swab use for ear cleaning
  • Fingernail scratching
  • Insertion of foreign objects
• External devices 1
  • Hearing aids
  • Earplugs
  • Earbuds
• Aggressive cerumen removal 1, 5

3. Dermatologic Conditions

• Eczema/atopic dermatitis - chronic pruritus with erythema, scaling, lichenification 1
• Seborrheic dermatitis - greasy yellowish scaling with secondary inflammation from Malassezia yeast 1
• Psoriasis - characteristic skin lesions 1
• Contact dermatitis 1
  • Irritant contact dermatitis - direct chemical damage from acids or alkalis
  • Allergic contact dermatitis - reaction to:
    • Metals (nickel, silver)
    • Chemicals in cosmetics, soaps, shampoos
    • Plastics in hearing aids
    • Otic preparations (especially neomycin)

Anatomical Factors

• Narrow ear canal - restricts airflow and drainage 1
• Exostoses - bony growths that can trap moisture and debris 1, 4
• Canal obstruction from:
  • Impacted cerumen
  • Foreign objects
  • Dermoid cysts
  • Sebaceous cysts
  • Furuncles 1

Microbial Factors

• Bacterial infections - most commonly:
  • Pseudomonas aeruginosa
  • Staphylococcus aureus 2, 6
• Fungal infections - particularly in:
  • Humid environments
  • After antibiotic treatment
  • Immunocompromised patients 2, 6

Other Contributing Factors

• Middle ear disease with otorrhea 1
• Immunocompromised state - increases susceptibility to infection and recurrence 2
• Diabetes - associated with increased risk of severe infections 2, 4

Prevention of Recurrence

To prevent recurrent episodes, the American Academy of Otolaryngology-Head and Neck Surgery recommends:

1. Avoid moisture accumulation:

   • Keep ears dry during bathing/showering using cotton with petroleum jelly 2
   • Avoid swimming during active infection 2
   • Use a hair dryer on low setting to dry ears after water exposure 5

2. Avoid trauma:

   • Do not insert anything into the ear canal, including cotton-tipped swabs 2
   • Minimize manipulation of the external auditory canal 5

3. Prophylactic measures:

   • Use acidifying solutions (2% acetic acid) after water exposure 5
   • Consider prophylactic eardrops for those prone to recurrent infections 2, 5

4. Manage underlying conditions:

   • Treat dermatologic disorders appropriately 1
   • Control diabetes and other systemic conditions 2, 4

Important Clinical Considerations

• Recurrent otitis externa requires thorough cleansing of the ear canal for proper diagnosis and treatment, but aggressive flushing should be avoided 5
• Patients with diabetes or immunocompromised states require closer monitoring due to risk of necrotizing (malignant) otitis externa 2, 4
• Distinguishing otitis externa from otitis media is crucial for appropriate treatment 1, 2

By identifying and addressing these underlying causes, most cases of recurrent otitis externa can be effectively managed and prevented.