Otitis externa refers to an infection of the ear canal, the tube leading from the outside opening of the ear in towards the ear drum. The ear canal is a tube about 2.5cm long, made partly of cartilage (outer third) and partly bone (inner two-thirds). The lining of the canal is skin which contains the glands which produce a waxy substance called cerumen (commonly called earwax). Cerumen is designed to protect the ear canal, repel water, and keep the ear canal too acidic to allow bacteria to grow.
Bacteria, fungi, and viruses have all been known to cause this type of ear infection. The commonest are various types of bacteria (pain and discharge often occurs), but fungi are also common (usually associated with intense itchiness).
Otitis externa occurs most often in the summer months, when people are swimming more frequently. Continually exposing the ear canal to moisture may cause significant loss of cerumen. The delicate skin of the ear canal, unprotected by cerumen, retains moisture, becomes irritated and with loss of the acidic properties that restrict growth of any bug, easily infected. The warm, dark, moist environment thus encourages the growth of the infecting organism.
Cleaning the ears with cotton buds (or worse objects eg knitting needles!) pushes the wax and debris back down the canal, working against the normal cleaning mechanisms of the skin and further promoting the development of otitis externa.
Patients with underlying skin problems such as eczema or psoriasis, or anatomical problems such as exostoses (surfer’s ear) may be more prone to otitis externa.
The ear is itchy at first. It then becomes quite painful, particularly if the outer part of the ear is touched or moved. If the canal is sufficiently swollen, hearing may become muffled. The canal may appear swollen or red, and there may be evidence of greenish-yellow pus. In severe cases there may be an accompanying fever with swelling of the outer ear and enlarged tender lymph nodes in front of or behind the outer ear.
The symptoms alone are characteristic but if there is a doubt, the ear can be swabbed to obtain a specimen. This is then cultured to determine what organism has infected the ear and what treatment is best. How is Otitis Externa Treated?
The two mainstays of treatment are to keep the ear dry until the infection has settled, and to avoid self-cleaning with cotton buds. If these are not done, the infection will be much harder to control.
If the ear gets wet too soon, if it is scratched or picked at, or if the treatment doesn’t kill the organisms, recurrence is common. Attention to these problems should allow early control of the condition.
Sometimes the skin of the ear canal behaves in an eczematous manner after prolonged otitis externa and needs ongoing maintenance treatment to bring it under control.