External otitis is a diffuse inflammation of the skin of the ear canal causing pain, itching, discharge, scaling, redness or swelling, and may be accompanied by hearing loss. The aetiology and pathophysiology are not entirely clear, but it appears that a disrupted acidic environment of the ear canal alters the local microbial flora and leads to inflammation. Normally, cerumen has a protective and bactericidal effect in the ear canal with its lipidic and acidic characteristics. 

Acute external otitis is most common in summer. Swimming and other water exposure is a well-known risk factor. Other external factors are soap and shampoo, altering the pH. Furthermore, occlusion of the ear increases moist and irritation of the ear canal. It is assumed that ear picking and ear cleaning may lead to external otitis by removing cerumen and creating skin abrasions. A narrow ear canal is considered a predisposing factor. 

1. aeruginosa is an important micro-organism causing external otitis. This bacterium is sensitive to acidifying therapy. In <10% of patients with otitis externa, culture shows a fungus, e.g. Aspergillus or Candida albicans. In the absence of a causative micro-organism, a contact allergy, psoriasis or eczema may have contributed to the development of external otitis. 

The diagnosis is based on a typical history and physical examination. Treatment consists of cleansing the ear canal from debris, enhancing the penetration of topical ear drops, followed by acid ear drops containing corticosteroids. If the tympanic membrane is not intact, aluminium acetotartrate ear drops should be prescribed. An ear wick drenched in ear drops can help to decongest a swollen ear canal. Cleansing and continued treatment are indicated if improvement lacks after one (or two) weeks. A culture with resistance determination is advised when treatment fails after three weeks. Patients should be educated about external factors that may elicit external otitis. Systemic antibiotics are only indicated in the case of fever and general illness. Analgesics can be used if necessary. 

The prognosis of acute external otitis is good: more than 75% of the patients are free of symptoms after three weeks of treatment. 

In ICPC-2, external otitis is coded with H70. The distinction with an acute otitis media with tympanic mebrane rupture, coded with H71, can sometimes be difficult.

External otitis has an incidence of 12.8 per 1000 patient years, meaning almost 13 new diagnoses among 1000 patients in a year. The incidence increases with age. In the age group 75+ the incidence is 25.5 per 1000 patient years in men and 17.0 in women. Link/Figure 1

Prevalence of external otitis is 16 per 1000 patient years, meaning that among 1000 patients in a year 16 seek help from their GP for external otitis. The higher prevalence number compared to the incidence number implies that external otitis sometimes requires prolonged attention of the GP. In men the prevalence is highest in the age group 75+ (35.3 per 1000 patient years), in women the prevalence is highest in the age group 65-74 (22.6 per 1000 patient years). Link/Figure 2 

Across all age groups, incidence and prevalence are roughly equal between men and women. 

Acute otitis media (H71) has an incidence of 19.6 per 1000 patient years (Link/Figure 3) and a prevalence of 18.8 per 1000 patient years (Link/Figure 4). Acute otitis media has the highest incidence and prevalence in the age group 0-4, while for external otitis, the occurrence is lowest in this particular age group.

By far, the commonest initial reason for encounter (RFE) for external otitis is ‘Ear pain (H01)’, accounting for 43% of al RFEs. Other common reasons for encounter are external otitis, plugged feeling ear, ear discharge, and a request for otoscopy or for medication. Link/Figure 5

The commonest intervention coded for external otitis is prescription of medication, in 92% of episodes. Ear flushing is recorded in only 6% of all episodes. Referrals to a medical specialist and microbiological tests occurred occasionally, in 4% and 2% of episodes respectively. Link/Figure 6

Most prescribed medication types are ear drops containing a combination of corticosteroids and other (anti-infective) medication (S02C), in 76% of all episodes. This concerns acid ear drops with hydrocortisone or with triamcinolone acetonide. This is followed by ear drops with (single) anti-infective medication (S02A), including aluminium acetotartrate and acetic acid, in 10%. Penicillins (J01C) are prescribed in 4%. Link/Figure 7