Ear infections develop primarily from an over production of ear wax. This comes as a result of irritation to the ear canal.

The ear canal is lined with skin. So any irritant that would affect their hair or body coat will also cause the same reaction within the ear.

The moisture of the wax and the temperature of the ear canal allow for a perfect environment for bacteria and/or yeast to grow. When this happens is diagnosed as an "infection". As the abundance of wax, bacteria and/or yeast increases the mixture will soon be joined by pus.

Otitis Externa refers to the entire ear canal up until you reach the tympanic membrane (ear drum). This is important because once an infection crosses the membrane it will lead to middle and inner ear infections.