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, humans, and various other species.
- Atopy (atopic dermatitis)
- Flea bite sensitivity
- Food allergy
- Emotional/behavioral problems
- Staphylococcal furunculosis
- Joint pain
In a 2006 study of 559 canine skin 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 continue to fuel the itch-lick cycle. In some dogs with ALD, the licking releases endorphins, which can soothe the dog, reduce anxiety, and suppress pain perception.
Both males and females can have lick granulomas, and dogs of any age 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, because they need 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.
Diagnostic tests include physical examination, skin cell examination, biopsy/histopathology, radiographic examination (X-rays), and skin culture.
- Treating the physical cause(s)
- Identifying and correcting the mental or emotional causes. (This may be accomplished by increasing the amount of human contact, changing kenneling habits, providing other animal companionship, distracting with chew toys, etc.)
- Drug treatment options (including sedatives/tranquilizers, endorphin blockers, corticosteroids, antidepressants, antibiotics, and pentoxifylline).
- Surgical removal of the lesion
- Radiation therapy
- Prevention of licking (bandages on the lesion, application of bad-tasting substances, e-collars, etc.)
- 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. Periodic re-check examinations and skin tests may also be needed.
The prognosis is fair. Treatment can take months. This condition is difficult to control, so owner compliance and dedication are vital to resolving the problem.