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Otitis Externa


Otitis externa is a broad term used to describe an inflammatory condition affecting the ear canal, with or without infection. The inflammation is usually generalised throughout the ear canal and can affect the outer ear. Acute otitis externa is the most common form. There are a number of popular synonyms such as ’hot weather ear’, ’tropical ear’ and ’swimmer’s ear’.

Acute otitis externa typically presents with pain or discomfort within the ear canal which is worsened if the outer ear is touched or pulled gently. The affected ear can feel blocked or full. Discharge from the ear canal can occur. If the ear canal becomes very swollen the patient may also complain of hearing loss.

Acute otitis externa occurs following a disturbance in the normal protective acidic milieu within the ear canal, secondary to a complex interaction of environmental and host factors.

Environmental factors comprise the following.
• Moisture - macerates the skin of the canal, elevates ear canal pH and removes the protective layer of cerumen (e.g. swimming, perspiration, high humidity).
• Trauma - leads to a breech in the integrity of the ear canal skin (e.g. cotton buds, fingernails, hearing aids, ear plugs, paper clips, match sticks, mechanical removal of cerumen).
• High environmental temperatures.

Host factors are as follows.
• Anatomical - wax and debris accumulate and lead to moisture retention (e.g. a narrow ear canal, hairy ear canal).
• Cerumen - absence or overproduction of cerumen (leads to loss of the protective layer and moisture retention respectively).
• Chronic dermatological disease (e.g. atopic dermatitis,
psoriasis, seborrhoeic dermatitis).
• Immunocompromise (e.g. chemotherapy, HIV, AIDS).

Regional dissemination of infection can lead to myringitis, auricular cellulitis, perichondritis, facial cellulitis and systemic toxicity. It may progress to chronic otitis externa and can lead to ear canal stenosis. Necrotising otitis externa is a life-threatening extension of otitis externa into the temporal bone resulting in osteomyelitis. It is caused almost exclusively by Pseudomonas aeruginosa and occurs most often in elderly patients with diabetes mellitus and in the immunocompromised.

The mainstays of treatment in primary care are the use of a topical antimicrobial (antiseptics or antibiotics, with or without steroids)and avoidance of precipitating factors. Management of pain is also required. Insertion of a medicated wick is recommended if the ear canal is swollen.Patients with copious amounts of debris and discharge within the canals responds well to ear cleaning (dry-mopping or suction) followed by a further course of topical therapy.

Prevention involves avoidance of predisposing factors and the treatment of any underlying dermatological condition. Any selfinflicted trauma to the ear canal should be eliminated. Frequent washing of the ears with soap should be avoided as the alkaline residue neutralises the acidic pH the ear canal.With regard to water, two options are available: the first is to observe strict water precautions (preventing water entering the ear canal) whilst bathing or swimming through the use of ear plugs (kept clean to prevent re-infection), a bathing cap, or application of cotton-balls smeared with petroleum jelly (Vaseline) to cover the ear canal entrances. The second option is ensure the ear canals are emptied of water after bathing or swimming, either by tilting the head and pulling on the ear to help empty it, or using a hair dryer on the lowest heat setting to dry the ears.

Around 9% of otitis externa is caused by fungal infection.Otomycosis is most commonly caused by Aspergillus (80–90%) or Candida species. There are anecdotal reports of fungal infection after repeated topical antimicrobial
treatments.The two most common species are Aspergillus niger andCandida albicans. Clotrimazole is the most widely used topical antifungal used.

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