Abnormal Ear Discharge in Cats and Dogs

The ear canals are lined with glands that produce a greasy, waxy substance called ear wax or cerumen. These ceruminous glands normally produce a colourless coating that keeps the ear tissues from drying out. This cerumen also helps to discourage growth of bacteria and yeast. Sometimes however, the ear environment becomes a favored home to organisms due to the warmth, protection, and moisture found there. Ear mite parasites also enjoy the microenvironment of the ears, and though these most commonly affect kittens, cats of any age can develop infestations. When the ear is irritated the production of cerumen increases, and bacteria use the cerumen as a food source. This turns it rancid and produces a foul greasy smell and darkening of the cerumen colour.

In humans, the ear canal is straight and so pooling of discharge is unlikely unless wax becomes dried out and clumps in the canal. On the other hand, dogs and cats' ear canals extend down towards their lower cheek as the canal extends in from where the canal entrance to the terminus at the eardrum (tympanic membrane) deep in the skull. This unfortunately provides a great spot for secretions or fluid to accumulate because gravity does not drain it. When dogs and cats shake their heads, they are sometimes attempting to clear secretions or discharge pooled in the horizontal canal next to the tympanic membrane. Bacterial infections in dogs often follow a swim or a bath because water and bacteria pool in the ear.

Abnormal smell, texture or colour of the ear secretion helps us identify infections or parasite infestations. The ear itself also becomes very sensitive, and the ear canal and inside of the flap (pinna) may become bright red associated with the inflammation. Left unattended, infected ears will become very painful and long-standing cases can even lead to deafness. Accumulation of large amounts of debris can press on the tympanic membrane and pop it, or extension of a severe infection can weaken and rupture a tympanic membrane. Once an eardrum is broken, the discharge and organisms can travel into the middle ear, and even extend into sensitive surrounding tissues of the head. These advanced cases can be difficult to clear without extensive medical therapy, and sometimes, surgical drainage is also required to affect a cure for these cats.

Bacterial infections often produce a foul-smelling discharge. If the ear(s) develop a pronounced infection, fever and loss of appetite are some signs that may be noted. Fungal (yeast) infections may be found in association with a bacterial infection, or on their own. These infections may produce pronounced scratching and head shaking, but if they are very painful, the pet may just flinch and vocalize if the ears are touched.

Ear mites often produce a characteristic dry brown-black discharge that is crumbly (we refer to it as "coffee ground"). Mites can produce extensive inflammation, and once they get going secondary bacterial and yeast infections often develop. The itchiness (pruritis) can be so intense with ear mites that the cat will develop large sores around the ears, particularly behind the ear pinnae due to vigorous repeat scratching episodes.

A pet showing signs of abnormal ear discharge, itchiness, pain, redness, swelling or bad odour should be taken to a veterinarian for assessment. In addition to a visual examination, an otoscope or videoscope will be used to visualize the ear canal down to the tympanic membrane. Discharge may be swabbed to check under the microscope for yeast organisms, ear mites, or stained with dye to identify bacteria type. Sometimes other recommendations may be made such as a culture of the discharge for bacterial sensitivity to antibiotics. If there is suspicion that the condition is affecting the eardrum or deep ear tissues, an X-ray (radiograph) will be performed to assess that area further.

Early treatment leads to a better prognosis, and some conditions worsen quickly without intervention, so care should not be delayed. Many excellent preparations are available to flush out the debris, clean the ear, and kill the parasites or organisms. Follow-up treatments at home with prescription preparations should be given according to the prescribed schedule.