SYMPTOM
Flank sucking
The owner sees the dog gripping or mouthing a fold of skin along its own flank with its lips or teeth and holding this position, sometimes for extended periods, most often when the dog is settling to rest or left with little to occupy it.
Breed-Associated Compulsive Behaviour
Flank sucking is most recognised in Dobermanns, where a genome-wide association study identified a risk locus on chromosome 7 within the CDH2 gene. Onset is typically before one year of age, and the behaviour can begin as a response to conflict or frustration before becoming more automatic with repetition.
Gastrointestinal Discomfort
Gastrointestinal disease is among the medical causes ruled out before an oral repetitive behaviour is treated as compulsive. In a study of a related oral behaviour, excessive licking of surfaces, most of the dogs had gastrointestinal disease, including lymphocytic-plasmacytic inflammation of the gut and chronic pancreatitis, and the licking resolved in about half once that disease was treated. The same link has not been shown for flank sucking itself, but gut discomfort has not been excluded as a trigger. Separately, flank and blanket sucking in Dobermanns are associated with a higher prevalence of pica.
Anxiety or Stress-Related Displacement
The behaviour can emerge as a coping response during understimulation, separation, or a change in routine or environment. In this pattern, flank sucking functions as a self-soothing or displacement activity rather than reflecting a physical source of discomfort.
Learned or Reinforced Habit
Owner attention, whether encouraging or attempting to interrupt the behaviour, can inadvertently reinforce it over time. What began as an occasional response to a specific trigger may become more frequent simply through repetition and reward.
Boredom or Under-Stimulation
Insufficient physical or mental enrichment, particularly in working or high-drive breeds kept in a lower-activity household, can lead to displacement behaviours including flank sucking during quiet periods.
Why timing matters
Early observation
In young dogs, particularly Dobermanns, onset before one year of age is consistent with the genetic and compulsive pathway described in breed studies, and episodes may be brief and situational at this stage. An early presentation limited to specific contexts, such as settling for rest, may still be evolving rather than fixed. At this point the behaviour may be more easily interrupted by a change in activity or environment.
Later presentation
Established, longstanding flank sucking that has become frequent, prolonged, or difficult to interrupt suggests the behaviour may have become self-reinforcing independent of its original trigger. At this stage, distinguishing a possible gastrointestinal contribution from a now largely habitual pattern becomes more relevant. Skin changes or localised hair loss at the sucking site can also develop with sustained repetition.
Comparing frequency, duration, and the contexts in which episodes occur over several weeks provides more useful information than a single observed episode. A pattern that intensifies or begins appearing alongside other repetitive behaviours may indicate the underlying driver is changing. A stable, predictable pattern confined to specific low-stimulation moments, by contrast, may point towards a settled behavioural trait.
Conditions commonly associated
Flank-Sucking in Dobermanns
This is the specific, breed-linked presentation of the behaviour, with an identified genetic component in Dobermanns and typical onset before one year of age.
Compulsive Behaviour in Dogs
Flank sucking is one recognised form of canine compulsive disorder, alongside other repetitive behaviours that may co-occur with it.
Generalised Anxiety in Dogs
Underlying anxiety can act as a driver or maintaining factor for repetitive, self-soothing behaviours including flank sucking.
Pancreatitis in Dogs
Chronic pancreatitis was among the diagnoses in a study of dogs with excessive licking of surfaces, a related oral behaviour. No direct link with flank sucking has been shown.
Gastroenteritis in Dogs
Gastrointestinal disease is one of the medical causes ruled out before an oral repetitive behaviour such as flank sucking is considered compulsive.
Inflammatory Bowel Disease in Dogs
Lymphocytic-plasmacytic inflammation of the gut was found in dogs studied for excessive surface licking, another oral repetitive behaviour. Whether it plays a part in flank sucking is not known.
Pica in Dogs
Dobermanns with blanket or flank sucking have a documented higher prevalence of pica.
Tail-Chasing in Dogs
Another recognised canine compulsive behaviour that can co-occur with flank sucking as part of a broader repetitive behavioural pattern.
When to explore further
Behaviour appearing in a Dobermann, particularly one with a known family history, given the identified genetic component, may benefit from behavioural characterisation rather than being dismissed as a simple habit.
When flank sucking is accompanied by episodes of vomiting, reduced appetite, or weight change, a gastrointestinal contribution may be worth characterising alongside the behavioural picture.
A sudden onset in an adult dog with no previous history, particularly in a breed not typically predisposed, may reflect an acute source of discomfort rather than a primary compulsive pattern.
Where the behaviour cannot be interrupted by normal distraction or has intensified to the point of self-trauma such as hair loss or skin damage, the intensity itself adds useful information.
Co-occurrence with other repetitive behaviours such as tail chasing, air licking, or pica may suggest a broader pattern worth documenting together rather than in isolation.
A brief video capturing the posture, duration, and what precedes or interrupts an episode can add useful objective detail beyond a verbal description. Noting the time of day, the dog's activity level beforehand, and whether episodes coincide with feeding, rest, or a particular location can help characterise likely triggers. A simple frequency log kept over a fortnight allows any change in pattern to be tracked objectively rather than relying on impression.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS