Acral Lick Dermatitis
By Margot Schwag, VMD
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Acral Lick Dermatitis (ALD), commonly referred to as lick granulomas, acral pruritic nodules, or neurodermatitis are thick firm plagues of bare skin located on the carpus (wrist), nocks (ankles), or digits (toes) of dogs and cats usually caused by compulsive licking by the animal.
At highest risk of developing these lesions are Abyssinian and Siamese cats. Dobermans, Danes and German Shepherds top the hit list for dogs, although any active "emotional" dog may be affected when placed in a situation they decide is stressful or boring. Local irritations such as cuts, bruises, and scrapes, can also be responsible for bringing the dog’s attention to the area. Additional underlying causes that initiate self-mutilation include foreign bodies, deep skin infection, underlying joint, muscle, or bone disease.
In the majority of cases, the dogs relieve their anxiety, loneliness, confinement or boredom by constantly licking. Eventually they remove the hair and erode the skin which causes the area to become inflamed. The area then becomes “itchy” so the dog licks more; thus, a viscous cycle is born.
Most ALD lesions can be diagnosed at an office exam, although they can be confused with tumors, pressure point calluses, bacterial infections, fungal, or yeast infections. History, biopsies, and radiographs to look at underlying bone may be required to make a definitive (final) diagnosis. Lesions over joints may be associated with arthritis or “freezing” (immobilization) of the joint.
While diagnosis is the easy part of this disease, treatment can be very difficult. Since this can be obsessive compulsive behavior, not only must the skin be treated, but more importantly, the mind must be pacified as well. Some dogs may be amenable to treatment; however, some dogs may never be cured.
Treament usually starts with evaluating the dog’s environment to see if the cause of licking can be detected. Hopefully, changes can be made. Medical treatment to assist the dog’s behavior is varied. Some doctors have had good success with phenobarbital, a medication used in the treatment of epilepsy. Tranquilizers may be used in dogs susceptible to acute stressful situations (fire-works, etc.). Progestogens can calm dogs down (especially males); however, they can have potentially dangerous side effects if misused.
New drugs on the horizon include Clomipramine (Anafranil: CIBA), a drug used in humans for the treatment of obsessive behaviors. Side effects are minor and toxocologic studies indicate it is safe for use in dogs. Other tricyclic antidepressants used include Amitriptyline (Elavil) and Imipramine (Tofranil: CIBA).
Prozac (Fluoxetine: Dista) is an anti-depressant and anti-serotonin agent (a chemical responsible for transmission within the brain). It has also been tried with some success. Some dogs have been unexpectedly cured of ALD when treated for hypothyroidism. The drug Naltrexone (Trexan) aids in endorphin release from the brain. These chemicals affect the pleasure centers of the brain. It is believed that if we can stimulate the release of endorphins with the Naltrexone, the dogs won’t feel the need to lick themselves and they will allow the lesions to heal.
Treatment of the actual lesion is also varied. Some people have done well with avoidance techniques: bandages, Elizabethan collars, muzzles or the application of foul tasting liquids or creams.
Historically, practitioners have used topical corticosteroids with or without DMSO (Dimethylsulfoxide—a vehicle to enhance drug absorption and an anti-inflammatory agent). Intralesional injections (injections directly under/into the lesion) with steroids can be helpful early on and with small lesions (less than three centimeters). Surgical correction is usually very disappointing as is radiation therapy. Cryosurgery may be tried but only if all else has failed.
I have found that treating these dogs with appropriate antibiotics has been wonderfully effective in clearing the lesions; however, unless stress, etc., is reduced, the dog will be back with future lesions.
This is truly one disease where I regret not being able to talk with my patients. They could tell me what is upsetting them and I could talk them through not mutilating themselves any longer. Although his disease is not life-threatening, some owners reach the point where they want to kill their pet with their bare hands! It can be very frustrating to treat one lesion and then have the dog start on a new area.
Remember, in most cases we need to identify and correct any underlying lesions and identify and correct what is upsetting the animal, as well as treat the wound.
© 1992 Margot B. Schwag, VMD. All rights reserved. For permission to reprint contact author at Landisville Animal Hospital, 3035 Harrisburg Pike, Landisville, PA 17538.