An acute, diffuse and painful bacterial infection of the skin of the external auditory canal.
The chief agents responsible for the development of acute diffuse otitis externa are local trauma and moisture.
The patient may only reluctantly admit to the use of a fingernail, hair grip (bobby pin) or cotton tipped applicator to clean the ear.
The entry of water after showering or swimming, or exposure to a hot and humid climate are also important predisposing factors.
Gram negative bacteria, principally Pseudomonas aeruginosa, can be cultured in almost every case.
These include pain, which is often severe, irritation, a blocked feeling within the ear, otorrhoea, itching and hearing loss when the canal is occluded by debris or swelling of the lining epithelium.
The skin of the external canal is swollen, extremely tender, and shiny in appearance. A peau d'orange appearance is occasionally seen, due to lymph edema.
It is frequently impossible to examine the tympanic membrane if the lumen of the meatus is obliterated.
In severe cases, the ear is so tender that even the gentlest movement of the pinna causes pain, and the introduction of the smallest speculum available is resisted by the patient.
Whitish mucopurulent material is often present within the canal and usually wax is absent.
In chronic cases, resistant to therapy, care should be taken that one is not dealing with an aminoglycoside or other antibiotic skin sensitivity. This is an unusual but not unknown response to neomycin, which is a frequent ingredient in many antibiotic containing ear drops. There may also be a sensitivity to other constituents of the topical preparation, including the carrier medium, such as propylene glycol.
If mucus is seen in the canal, then there is a high likelihood of a perforation in the tympanic membrane, since there are no mucus producing glands within the external canal. Chronic cases of otitis externa may sometimes be caused by an unsuspected middle ear infection pouring secretions into the canal through a small perforation which cannot be seen because of the generalized swelling of the canal skin.
The cartilaginous external auditory canal is edematous and the lumen is narrowed to a slit.