Narrowing testing because of financial constraints
Many clients have financial constraints that limit the diagnostic tests that can be done on the first visit. However, a patient's
signalment, history, and other factors can guide you in determining whether a medical or behavioral cause is more likely.
Age. If the dog is middle-aged or older, evaluate medical causes most closely. If the licking behavior appears suddenly in a geriatric
dog, question the client closely about other clinical signs suggestive of cognitive dysfunction. In my opinion, it is unlikely
for a middle-aged or older dog with a placid temperament and no history of anxiety-related behaviors to suddenly develop a
stereotypy or compulsive disorder. Most repetitive behaviors in people develop at or before adolescence.7 Barbering in mice and feather plucking in psittacines (behaviors that are being considered as possible models for some human
repetitive disorders) develop before or around the time of sexual maturity.8,9 Although it is possible that an adult animal might experience an event leading to an anxiety- or conflict-related disorder
(e.g. displacement or redirected behavior), in older animals, consider a medical cause more likely than a compulsive disorder.
Breed and temperament. Many breeds may have a genetic predisposition for certain compulsive disorders (Table 1).10 Although excessive licking of surfaces is not a compulsive disorder that has been observed more in a particular breed, a
dog that is susceptible to one type of oral compulsive behavior may be at risk for other anxiety-related behaviors. In addition,
in my opinion, some dogs are born with a shy or fearful temperament that can predispose them to anxiety-related behaviors
when faced with frustrating or conflicting experiences. So when presented with a dog that has a history of other anxiety-related
behaviors, a behavioral cause for the licking could reasonably be moved higher on the differential diagnosis list.
Table 1: Breed Predilections for Compulsive Behaviors*
Persistence of the problem. If the behavior has been present for an extended period (months to years), then a medical cause is unlikely. If a medical
cause were contributing to a licking behavior that has been present for several months, clinical signs suggestive of an ongoing
or progressive disease process should have already developed or worsened.
Presumptive GI upset. If you suspect nausea but cannot identify its cause and are limited in the diagnostic tests the owners will allow, consider
presumptive treatment for gastrointestinal upset. If a course of famotidine (0.5 to 1 mg/kg orally once or twice a day) alone
or in combination with metronidazole (10 to 15 mg/kg orally b.i.d.)11 for seven to 10 days stops the licking behavior, then more extensive diagnostic tests could be readily justified to look
for the cause of the gastrointestinal upset.
Canine cognitive dysfunction
Dogs with cognitive dysfunction may display a variety of repetitive behaviors. But if the excessive licking behavior is a
result of cognitive dysfunction, then treatment will be different than it is in dogs without cognitive impairment.
If the patient is more than 11 years old, studies have shown that there is a good chance it is showing at least one sign of
Common signs of cognitive decline include confusion, changes in relationships with people and other pets in the household,
changes in activity level, disrupted sleep-wake cycles, and decreased ability to learn or remember commands (e.g. a previously well-housetrained dog may begin eliminating in the house).13 Cognitive dysfunction is a diagnosis of exclusion, so if a patient is showing signs of cognitive impairment along with repetitive
behaviors, then possible medical causes must be ruled out before you treat the behavior problems.
Treating cognitive dysfunction may help reduce the signs of repetitive behaviors. Treatment, which may include behavior and
environmental modification and drug therapy, is described elsewhere.13