Beta-endorphins, dopamine and serotonin have been implicated as underlying mediators in compulsive disorders.5 Studies on acral lick dermatitis (ALD) in dogs identified a similarity to human compulsive and impulsive control disorders
in that both human and animal models improved with clomipramine or selective serotonin reuptake inhibitor (SSRI) therapies.6
Dopaminergic drugs, such as amphetamines, have been reported to induce stereotypies,7 and dopamine antagonists have appeared to suppress stereotypies.8,9 Support that compulsive disorders are mediated through opioid receptors came from the use of naloxone to treat stereotypic
behaviors (e.g., self-licking, self-chewing, scratching behavior).10 Variable neurotransmitters may be involved in different behaviors. A genetic basis is suspected in many compulsive behaviors,
with certain breeds being over-represented in some behaviors (e.g., flank sucking in Doberman pinschers, tail chasing in herding
It has been proposed that patients with clinical atopic disease and other inflammatory diseases may be predisposed to behavioral
sequelae, in particular, reduced coping strategies and increased reactivity, anxiety and aggression.11 But this association wasn't apparent in a cross-sectional survey that evaluated 238 dogs classified as pruritic or nonpruritic.
No significant difference was found between these groups in aggression, anxiety or fearful behaviors.12
Overall, stress, conflict, anxiety and lack of environmental enrichment have been implicated as initiating or supportive factors
in the development of compulsive and stereotypic disorders. Over time, the consequences of these behaviors (i.e., medical,
learned, conditioned), changes in neurotransmitters and genetic predispositions help facilitate and sustain these behaviors.
Possible behavioral causes for these disorders include:
- Insufficient stimulation (e.g., crating, confinement, lack of exercise)
- Alterations in schedule or routine for owner or pet
- Inconsistent or improper training
- Anxiety-inducing situations
- Household changes
- Addition or departure of family members or other pets
- Situations of frustration.
Acral lick granuloma (or acral lick dermatitis): ALD is characterized by a firm, raised, ulcerated plaque of the skin secondary to chronic licking. Lesions generally are found
on the dorsal aspect of the carpus or metacarpus but also frequently over the metatarsus and tibia. ALD may be dermatologic,
neurologic or behavioral in origin or a combination of these.
From a behavioral perspective, a strong association appears to exist between anxiety and licking,13 but inadequate social interactions or lack of environmental stimulation and exercise also have been proposed as psychogenic
inciting causes. Displacement licking, which arises out of conflict or frustration, also is cited.5
Certain breeds appear to be over-represented, including Labrador retrievers, Great Danes, Doberman pinchers and German shepherds.
This supports a familial inheritance.6,13 Whatever the inciting cause, secondary bacterial infections complicate and continue to potentiate the pruritus through inflammatory
mediators and, thus, the persistent stimulus to lick.
Flank sucking: The Doberman pinscher is the breed most commonly seen to exhibit this poorly understood behavior. An affected dog will hold
a section of its flank in its mouth (Photo 2). Skin lesions are rarely associated with this disorder but can occur. Because
the trait has been followed through certain bloodlines of Dobermans, a hereditary component is suggested.5 The problem seems to occur more when a dog is under stress and occasionally becomes compulsive in nature. If the disorder
is mild, the owner may not wish to treat, as the behavior may be calming for the dog. However, if it begins to become compulsive
or causes skin lesions, then treatment should be applied.
Photo 2: A Doberman pinscher exhibiting flank sucking.