Canine Acral Lick Dermatitis, more commonly known as Lick Granuloma, is one of the most frustrating skin problems there is. What often seems like a simple problem is in fact multifactorial, and therefore attempting to treat it with a single approach are usually doomed to failure. There is usually an underlying cause, plus a secondary bacterial infection, plus an obsessive compulsive behavioral cycle to deal with.
Lick granulomas are most common in large, active, attention seeking breeds such as Dobermans, Rottweilers, Labrador retrievers, German Shepherds and Irish Setters. It can however happen in any breed, at any age.
The wound (lesion) develops as a result of the repetitive licking action of the animal. Chronic trauma to the site results in follicular rupture and furunculosis. The lesion is usually single, oval and varies in size from 2-6cm. It is usually found over the carpal (wrist) or metacarpal areas, though can also occur on the back leg. The lesion usually manifests as a raised, firm, hairless nodule or plaque and may have an ulcerated surface.
Almost without exception, lick granulomas are infected. Bacteria from the mouth are seeded in the lesion by the constant licking, which leads to the infection and a perpetuation of the licking cycle. In the early stages at least, the infection is usually by Staphylococcus species.
Identifying the Underlying Cause
Once it has been established that the dog does indeed have a lick granuloma, and not a skin tumor for example (usually obvious by clinical signs, though biopsy is definitive) then the dog must be examined for the presence of other skin, orthopaedic and neurological disease. A full clinical history and physical examination is mandatory. The following approach would be considered a very thorough one; most vets will simply bandage the leg and try a long course of antibiotics, sometimes successfully, but in the interests of those that cannot be fixed by this approach (and many cannot) I shall describe the thorough approach.
Skin tests should include skin-scraping, hair plucking, fine needle aspirates and/or a punch biopsy from a non-ulcerated area. A bacteriology swab should also ideally be taken for culture and sensitivity, to enable optimal antibiotic selection.
Orthopaedic investigation should include survey radiographs (Xrays) of the area, comprising at least 2 views, to look for bony lesions. If the lick granuloma is over a joint, then synovial fluid may be sampled.
For neurological assessment, a thorough knowledge of the nerves innervating the skin is required, and electromyography has been used to identify specific neurological deficits (this is realistically outside the realms of most practitioners).
Treatment of Medical Conditions
Lick granulomas are part infection, part behavioral and part other causes. After screening for underlying disease as described above, the next step is getting rid of any bacterial infection.
Topical antibiotic creams are useless in these cases. They only draw attention to the lesion from the dogs perspective, and perpetuate the licking. Systemic (oral) antibiotics are required, and are needed for a minimum of 3 weeks (and often up to 3 months). The choice of antibiotic is best made following bacterial culture and sensitivity, first line drugs often selected include cefalexin, amoxicillin and clindamycin. If resistance to these is suspected or confirmed, then more expensive antibiotics such as enrofloxacin (Baytril) or marbofloxacin (Marbocyl) can be prescribed.
Treatment of a Behavioral Problem
Many different treatments have been tried in order to break the compulsive behavioral component of lick granulomas. These include:
Corticosteroids (prednisone, medrone)
Non steroidal anti-inflammatory drugs (NSAIDs)
However, no one therapy has been consistently shown to resolve the problem without recurrence. Recent work has suggested that a combination of drugs and behavioral modification is the best approach.
The only drug currently licensed for behavioral therapy in the dog is clomipramine (Clomicalm). The main side effect of this is sedation, and it cannot be given to animals with pre-existing liver or kidney dysfunction. Better drugs for this purpose are the serotonin reuptake inhibitors (SRIs), such as sertraline and fluoxetine. These SRIs have less side effects and can be used long term, but have a slow onset of action so when being trialed, must be given for a minimum of 4-6 weeks before any judgment is made as to efficacy.
Behavioral modification depends on the cause of the stress involved. For fear and anxiety related stress, avoid leaving the dog alone, leave the dog in a favored place (e.g. car) or vary the arrival and departure routine so that the dog does not realize its owner is going out.
For boredom related stress, increase the visual or auditory stimulation by providing new toys, leaving the radio or TV on etc.
For attention-seeking stress, ignore stereotypical behavior to avoid reinforcement, and do not punish the behavior as this may lead to anxiety and complicate matters.
To conclude, lick granulomas are a difficult disease to manage. However, if the veterinarians approach is logical, then appropriate investigation, together with antibiotic treatment, behavioral drugs and behavioral modification, can achieve a high degree of clinical resolution if not always a complete cure.