Otitis externa
What is otitis externa?
Otitis externa is an inflammatory condition of the external auditory canal (the ear canal). It is characterised by redness, swelling, scaling and thickening of the canal skin lining and is accompanied by varying degrees of discomfort, itch, deafness and discharge.
What causes otitis externa?
The causes of otitis externa can be split into two main groups: those caused by bacterial or fungal infection and those by non-infectious dermatological conditions. Bacterial infections are the most common cause of otitis externa. Primary skin disorders are often precipitants of infectious otitis externa, but they can also be the sole cause of otitis externa.
Infectious otitis externa
As with all skin the external auditory canal has a normal bacterial flora that remains free from infection until skin defences fail or become damaged. Some common causes that allow the overgrowth of bacteria in the external ear include:
- Swimming, perspiration, high humidity – these create excessive moisture that carry bacteria into the cerumen (ear wax) of the ear canal, leading to maceration and inflammation
- Local trauma to the ear canal allowing bacteria to enter damaged skin, e.g. insertion of objects such as cotton buds, matchsticks and fingers to relieve itching or impacted earwax
Bacteria commonly implicated in otitis externa include Pseudomonas aeruginosa and Staphylococcus aureus. In about 10% of cases of infectious otitis externa, fungal infections are the cause. The most common fungal pathogen is Aspergillus (80-90%), followed by Candida. Mixed bacterial and fungal infections are common.
Non-infectious dermatological causes
Otitis externa caused by dermatological conditions are often referred to as “eczematous otitis externa”. Skin conditions that may cause otitis externa include:
- Atopic dermatitis (eczema)
- Psoriasis
- Seborrhoeic dermatitis
- Acne
- Cutaneous lupus erythematosus (rare)
- Irritant or allergic contact dermatitis – from local irritants, including topical preparations or use of hearing aids or ear plugs
Often the condition is complicated by secondary bacterial infections.
What are the signs and symptoms?
The most common symptoms of otitis externa are otalgia (ear discomfort) and otorrhoea (discharge from the external auditory canal). Ear discomfort can range from pruritus (itching) to severe pain that is worsened by motion of the ear, e.g. chewing. Discharge from the ear varies between patients and may give a clue to the cause of the condition. Swelling within the external auditory canal may cause feeling of fullness in the ear and loss of hearing. The clinical features of otitis externa may vary according to the cause.
| Cause | Clinical features |
|---|---|
| Bacteria |
|
| Fungi |
|
| Atopic dermatitis |
|
| Psoriasis |
|
| Allergic contact dermatitis |
|
| Irritant contact dermatitis |
|
Otitis externa
How is the diagnosis made?
History taking and physical examination is often all that is required to make a diagnosis of otitis externa. If fever or signs of toxicity are present, perform standard laboratory testing. Gram staining and culture of the discharge may be helpful, particularly when a bacterial or fungal cause is suspected.
What treatment is available?
Initial treatment begins with cleaning debris and wax from the canal. Once the ear is cleaned specific treatment that is prescribed according to the cause of otitis externa should be administered. Occasionally if swelling in the ear is severe, a wick may be inserted before medication is applied, usually in the form of topical eardrops.
| Cause | Treatment options |
|---|---|
| Bacteria |
|
| Fungi |
|
| Systemic dermatological disease, e.g. psoriasis |
|
| Contact dermatitis |
|
Patients should be educated about how to prevent recurrences of otitis externa. Some simple general measures include:
- Wear a tight fitting swimming cap to prevent water entering the ear canal
- Attention to drying the ears after swimming or showering
- Patients prone to recurrences may use acidifying drops after swimming or water sports
- Avoid poking and scratching the skin of the external auditory canal as damage to the skin and removal of earwax makes the canal more vulnerable to infection
- Patients with otitis externa should preferably abstain from water sports for at least 7-10 days.
