Lick Granuloma in Dogs

Lick granuloma (also called acral lick granuloma, acral lick dermatitis, acral pruritic nodule, and ALD) is a common, stubborn skin disease. It is caused by a dog repeatedly licking an area of the body, usually the lower leg. The chronic, localized self-trauma leads to irritation of the skin, resulting in open sores. Lick granulomas may be mistaken for cancer or foreign body granulomas. Cats do not develop lick granulomas. However, lick granulomas can occur in cattle, people, and various other species.

Causes include:

• Atopy (atopic dermatitis)
• Boredom
• Flea bite sensitivity
• Food allergy
• Hypersensitivity
• Cancer
• Emotional/behavioral problems
• Staphylococcal furunculosis
• Wounds
• Joint pain

In a 2006 study of 559 canine dermatologic conditions in general veterinary practice, the prevalence of ALD was 2.9%. Allergies and behavioral conditions are common underlying ALD causes. However, ALD is likely due to multiple factors. Secondary bacterial infection occurs in both allergic and behavioral ALD. In a 2008 study involving 31 ALD cases, 97% (31/32) had a bacterial infection. Both a secondary infection and a foreign body reaction from ruptured hair follicles (furunculosis) keep the ALD going. An ulcerative skin lesion from the licking may become itchy and perpetuate the itch-lick cycle. In some dogs with ALD, the licking releases endorphins, which can be soothing, reduce anxiety, and suppress pain perception.

Both males and females can have lick granulomas. Any age dog can be affected. Breeds commonly affected include but are not limited to: Doberman pinscher. German shepherd, German short haired pointer, Golden retriever, Great Dane, Irish setter, Labrador retriever, and Pointer. This breed predisposition may be due to genetics or it could be due to the tendency of large breed dogs to be used as working and socially interactive dogs.  Boredom results in the dogs licking, for something to do.

Signs include hair discoloration, hair loss, skin sores, hyperplasia (an abnormal increase in the number of normal cells), fibrosis (formation of fibrous skin and tissue similar to gristle), lameness caused by the mass, and growth of the underlying bone. The lesions are usually solitary, but they can occur on more than one limb at the same time. The areas most frequently affected are the front and sides of the lower legs. In rare cases, lick granulomas can occur in the flank or at the base of the tail.

Diagnosis

Diagnostic tests include physical examination, skin cell examination, biopsy/histopathology, and skin culture.

Treatment

Treatments include:

1. Treating the cause(s)
2. Identifying and correcting the mental or emotional causes by increasing the amount of human contact, changing kenneling habits, providing other animal companionship, distracting with chew toys, etc. 
3. Medical treatment options include sedatives/tranquilizers, endorphin blockers, corticosteroids, antidepressants, antibiotics, and pentoxifylline.
4. Surgical removal of the lesion
5. Radiation therapy 
6. Prevention of licking (bandages on the lesion, e-collars, etc.) 
7. Applying bad-tasting substances to the granuloma
8. Acupuncture
9. Laser therapy

NOTE: No treatment is uniformly successful. ALD is hard to control or cure. You may need to try different treatments, because not every treatment works for every cause.

Prognosis

The prognosis is fair.  Client compliance is key to resolving the problem, and treatment can take months. Periodic re-check examinations and skin tests may be needed.