By definition, otitis externa represents a spectrum of inflammatory changes that occur to the external acoustic canal in response to any insult to the ear canal epithelium.

But what actually causes ear diseases? Can putting a bacterium or a yeast organism into a normal ear canal result in disease? Although there may be bacteria or yeasts found in the patient with otitis externa, these organisms are not the cause of the ear disease.

Trauma

Trauma to the ear canal from injury or inappropriate use of instruments in the ear can lead to primary inflammatory changes within the ear. Hair plucking with curved hemostats can result in traumatic inflammation of the ear canal and resultant infec­tion. A more common reason for trauma to the ear canals is the use of cotton-tipped applicators to clean the ear. Cotton-tipped applicators (Q-tips) and applicators with synthetic materials are very irritating to the epithelium when pushed into an ear canal. Their abrasive effect essentially debrides the layer of surface keratinocytes, which is normally very thin. This results in ulceration of the ear canal and exposure of the dermal elements to the resident bacteria and yeasts in the ear, leading to infec­tion. A Q-tip can also push accumulated material ahead of it as it goes deeper into the decreasing diameter of the ear canal. This may result in a hydraulic effect, with significant pressure and subsequent ruptured eardrum. Cotton-tipped applicators can be used to acquire a cytology sample and as an absorbent material. The cotton tip is laid onto liquid in the ear canal; the cotton absorbs the liquid and is then removed. Q-tips should never be used in a “mopping” motion, going in and out of the ear canal.