A lick granuloma, also known as acral lick dermatitis, is a skin disorder in dogs resulting from an urge to lick the lower portion of the leg. The lesion from the incessant licking is a thickened, firm, oval plaque.
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Lick granuloma is a form of self-trauma in which animals, particularly dogs, continuously lick a small area of their body until it becomes raw and inflamed. The most common areas affected are the lower (distal) portions of the legs. The most common cause of lick granuloma appears to be psychological, related to stress, boredom or compulsiveness. It is often considered to be a form of canine obsessive-compulsive disorder[1], but other less common causes include bacterial or fungal infections, trauma causing nerve damage, allergies, or joint disease. Hot spots may also lead to the formation of lick granulomas. Many large breed dogs appear to be predisposed.[2]
Lick granulomas are especially seen in large active dogs left alone for long periods of time. The condition becomes a vicious cycle - erosion of the skin from licking leads to pain and itching, which leads to more licking. One theory is that excessive licking causes endorphin release, causing an addiction to licking. Lick granulomas sometimes becomes infected with bacteria, causing abscessed areas or fistulous tracts (furuncles).
Treatment of the primary cause, if known, is essential. The dog should be tested for allergies, and treated accordingly if positive (fatty acids, antihistamines, hypoallergic diet, etc). It may also be necessary to check thyroid levels as hypothyroidism seems to play a role in some cases, particularly in black Labrador retrievers; thyroid medication often will resolve the problem if it's due to hypothyroidism. [4]
Recently, a new dermatology bioscaffold developed by TR Matrix evidenced a reduction in lesion size, inflammation, and improvement in hair growth in dogs with refractory distal limb lesions (pending abstract).
In psychogenic cases, dealing with psychological factors is most important. Factors should be identified such as being left alone all day, being confined, and changes in the household. Correction of these causes may include increased walks, avoiding confinement, and more interaction in the home.
Drugs may be used until behavior modification has had time to take effect. Antidepressants are most commonly used, including doxepin, amitriptyline, fluoxetine, and clomipramine. If the psychological factors are not corrected, the dog will usually relapse after the drugs are discontinued. Endorphin blockers such as naltrexone can be used to reduce addiction to licking, or endorphin substitutes such as hydrocodone may decrease the urge to lick.[3]
The lesion should also be treated. Licking can be prevented by the use of Elizabethan collars, battery enhanced wraps, bandages, antilicking ointments (which are bad tasting) and anti-lick strips. It is important to catch lesions early and keep the dog from licking to then reduce inflammation and development of a habit. Topical medications such as corticosteroids or DMSO may be effective if used early. Small lesions may be injected with triamcinolone or methylprednisolone. Oral antibiotics are used to control infection. Surgery may be performed to remove whole lesions, but there is risk of continued self mutilation to the area afterwards. Other potential treatments include cryosurgery, laser surgery, radiation therapy, and acupuncture. It is important to note that many dogs will lick at another leg, creating a new lick granuloma, if they are prevented from licking at the original one while it heals.
Overall, lick granulomas are very difficult to treat, with control only being achieved in about 65 percent of cases.[5]