External otitis is an infection
of the ear canal. The ear canals are delicate structures and are easily
infected. Eighty percent of infections occur in breeds with long, dropped ears.
This is a function of lack of air circulation; open, erect ears dry out more
easily than dropped ears and therefore provide less favorable conditions for
Many factors contribute to the development of external otitis. Some breeds
(such as the Chinese Shar-Pei) are predisposed because of narrow or stenotic
ear canals. Other breeds may be predisposed because they have an abundance of
hair that blocks the circulation of air. Many dogs with allergic skin diseases, particularly canine atopy and food
hypersensitivity dermatitis, are predisposed to ear infections as part of the
generalized skin response. Similarly, dogs with primary and secondary seborrhea often have ear canal involvement
characterized by a buildup of yellowish oily wax that provides an excellent
medium for bacterial growth. Foreign bodies such as grass seeds and foxtails,
and growths in the ear canal, are other predisposing causes. Ear mites can precede bacterial
Many dogs live peacefully with other animals, such as cats, rabbits, birds, and rodents. Not all dogs, however, are suited for a multi-species household. Introducing a dog to a small animal is potentially risky and needs to be planned carefully.
Iatrogenic causes of infection include using cotton-tipped applicators to
clean the deep recesses of the ears, allowing water to get into the ears during
bathing, excessive and improper cleaning of the ears,
and a grooming routine that calls for
plucking or clipping hair in the external ear canals.
Signs of external otitis are head-shaking and scratching and rubbing at the
affected ear. The ear is painful. The dog often tilts or carries her head down
on the painful side and cries or whines when the ear is touched. An examination
reveals redness and swelling of the skin folds. There usually is a waxy or
purulent discharge with a bad odor. Hearing can be affected.
Ceruminous otitis occurs with primary seborrhea. There is an extensive
buildup of oily, yellowish wax in the ear canals, which provides an excellent
medium for bacteria and yeast. Treatment is directed toward control of the
seborrhea. Regularly cleaning the ear canal may be necessary until this problem
Bacterial otitis, in its acute form, is usually caused by Staphylococci. The
discharge is moist and light brown. Chronic infections usually are caused by
Proteus or Pseudomonas bacteria. The discharge is generally yellow or green,
although there are exceptions. More than one species of bacteria may be
involved, which complicates antibiotic treatment.
Yeast or fungal infections may follow antibiotic treatment of bacterial
otitis. Yeast infections also occur commonly in dogs suffering from atopic
dermatitis, food hypersensitive dermatitis, and seborrheic skin diseases. A
brown, waxy discharge with a rancid odor is sometimes seen, or a very red,
inflamed, moist ear with minimal discharge. These infections tend to persist
until the underlying disease is controlled.