Inflammation of the ear canal with or without infection is the charecteristic of acute otitis externa. If symptoms are recurrent or if they last longer than three months, the condition is classed as chronic otitis externa. Acute otitis externa can also be classified according to its cause. These are split into three main groups: Infective (bacterial, fungal, and viral), Non-infective dermatitis (allergic, eczematous, and irritant), and Mixed infective and non-infective Exacerbating factors include: Warm humid climates, swimming, frequent hair washing (especially if in the bath), and inseion of foreign bodies can introduce bacterial infection and cause local trauma to the ear canal, making infection more likely. Prolonged use of hearing aids may also predispose to infection.