The etiology of AOE is multifactorial. Regular cleaning of
the ear canal removes cerumen, which is an important barrier to
moisture and infection.18 Cerumen creates a slightly acidic pH
that inhibits infection (especially by P aeruginosa) but can be
altered by water exposure, aggressive cleaning, soapy deposits,
or alkaline eardrops.19,20 Debris from dermatologic conditions
may also encourage infections,7,21 as can local trauma from
attempts at self-cleaning, irrigation,22 and wearing hearing
aids.23,24 Other factors such as sweating, allergy, and stress have
also been implicated in the pathogenesis of AOE.25