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# Otitis externa

Otitis externa, or swimmer's ear, is an infection of the [ear canal](https://durgical.com/en/anatomy/external-acoustic-meatus/), usually after moisture gets trapped; it causes ear pain and itching.

Updated 2026-10-29

## Structures involved

Tap one to see what it is and open it in 3D.

- [Ear canal](https://durgical.com/en/anatomy/external-acoustic-meatus/)
- [Auricle](https://durgical.com/en/anatomy/auricle/)
- [Eardrum](https://durgical.com/en/anatomy/tympanic-membrane/)
- [Temporal bones](https://durgical.com/en/anatomy/temporal-bone/)
- [Facial nerve (VII)](https://durgical.com/en/anatomy/facial-nerve/)

## Microorganisms that cause it

- [Pseudomonas aeruginosa](https://durgical.com/en/microbiology/pseudomonas-aeruginosa/)

## In the clinical exam

- [Otoscopy and the Rinne and Weber tests](https://durgical.com/en/clinical-exam/otoscopy-and-the-rinne-and-weber-tests/)

## What it is

Inflammation and infection of the external ear canal, usually bacterial. Often called «swimmer's ear» because moisture in the canal is the classic trigger.

## Who gets it

Common at all ages and most frequent in hot, humid climates and in swimmers. Necrotising (malignant) otitis externa is a rare, serious form seen mainly in older adults with diabetes or immunosuppression.

## Causes

- Pseudomonas aeruginosa (most common)
- Staphylococcus aureus
- Mixed and other gram-negative bacteria
- Fungi (Aspergillus, Candida), especially after long courses of antibiotic drops

## Risk factors

- Swimming, humidity and sweating that keep the canal wet
- Trauma from cotton swabs, fingernails or cleaning
- Hearing aids and earphones
- Loss of protective cerumen
- Skin conditions of the canal (eczema, seborrhoeic dermatitis, psoriasis)
- Diabetes or immunosuppression (risk of the necrotising form)

## Pathophysiology

Water and trauma break down the acidic, waxy barrier of the canal skin. Bacteria colonise the macerated skin, which swells and narrows the canal; inflammation can spread to the auricle and surrounding soft tissue. In the necrotising form, infection invades the temporal bone and skull base.

## Classification

- Acute diffuse (most cases)
- Acute localised (furuncle of the canal)
- Chronic (lasting more than about 3 months)
- Otomycosis (fungal)
- Necrotising (malignant) otitis externa

## Symptoms and signs

- Ear pain, often intense, worse when moving the tragus or pulling the auricle
- Itching
- Discharge from the canal
- Feeling of fullness and muffled hearing
- Swollen, red canal with debris

## Red flags

- Severe pain out of proportion with granulation tissue on the canal floor, in an older person with diabetes (necrotising otitis externa)
- Facial weakness or other cranial nerve palsy
- Fever with spreading cellulitis of the auricle or face
- Persistent symptoms despite correct treatment

## Diagnosis

**Clinical**
Based on history and otoscopy: tenderness on tragal pressure or pulling the [auricle](https://durgical.com/en/anatomy/auricle/), oedematous red canal with debris. The [eardrum](https://durgical.com/en/anatomy/tympanic-membrane/), when seen, is usually normal; fungal hyphae or spores suggest otomycosis.

**Tests**
Culture of the discharge in severe, recurrent or refractory cases. Glucose and inflammatory markers when necrotising infection is suspected.

**Imaging**
Not needed in uncomplicated cases. CT and/or MRI of the [temporal bone](https://durgical.com/en/anatomy/temporal-bone/), and sometimes nuclear scans, when necrotising otitis externa is suspected.

## Differential diagnosis

- Acute otitis media with perforation and discharge
- Furuncle of the ear canal
- Contact dermatitis of the canal
- Herpes zoster oticus (Ramsay Hunt syndrome)
- Cholesteatoma
- Foreign body

## Goal of treatment

Clear the infection, relieve pain and restore a dry, healthy canal, while spotting the necrotising form early.

## Treatment

**Medical**
Topical antibiotic drops, often with a corticosteroid, are first line; non-ototoxic drops (such as fluoroquinolones) are preferred when the eardrum may be perforated. Antifungal drops for otomycosis.

**Procedure**
Aural toilet (gentle cleaning by microsuction) so the drops reach the [skin](https://durgical.com/en/anatomy/skin/); a wick when the canal is too swollen.

**Conservative**
Keeping the ear dry, avoiding swabs and earphones during treatment, and analgesics for pain.

**Medical**
Systemic antibiotics when infection spreads beyond the canal or the patient is diabetic or immunosuppressed; prolonged antipseudomonal therapy for necrotising otitis externa.

## Drugs for this condition

- [Polymyxin B](https://durgical.com/en/pharmacology/polymyxin-b/)
- [Ofloxacin](https://durgical.com/en/pharmacology/ofloxacin/)

## Complications

- Spreading cellulitis of the auricle (perichondritis)
- Chronic otitis externa and canal stenosis
- Necrotising otitis externa with skull base osteomyelitis
- Cranial nerve palsies ([facial nerve](https://durgical.com/en/anatomy/facial-nerve/) first)

## Prognosis

Most acute cases improve within days of correct topical treatment. Necrotising otitis externa needs long treatment and can be fatal if diagnosed late.

## Prevention

- Drying the ears after swimming; earplugs for frequent swimmers
- Not using cotton swabs in the canal
- Acidifying drops in some recurrent cases

## Test yourself

Think of the answer, then tap the question to see it.

## Which bacterium causes most cases of acute otitis externa?

Pseudomonas aeruginosa, followed by Staphylococcus aureus.

## Which examination sign helps separate otitis externa from otitis media?

Pain on pressing the tragus or pulling the auricle.

## Which patient is at risk of necrotising otitis externa?

An older adult with diabetes or immunosuppression; it spreads to the temporal bone and skull base.

## What is the first-line treatment of uncomplicated acute otitis externa?

Topical antibiotic drops (often with a corticosteroid) after cleaning the canal; systemic antibiotics are not routine.

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## Related conditions

- [Acute otitis media](https://durgical.com/en/conditions/acute-otitis-media/)
- [Herpes zoster (shingles)](https://durgical.com/en/conditions/herpes-zoster/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Otitis Externa](https://www.ncbi.nlm.nih.gov/books/NBK556055/) (StatPearls (NCBI Bookshelf), 2023).

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Source: https://durgical.com/en/conditions/otitis-externa/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/otitis-externa/