One of the most frustrating conditions I treat in dogs is acral lick dermatitis (commonly called a lick granuloma). This condition most commonly occurs on the legs of large breed dogs. The condition starts as a discoloration of the fur. With more licking, the skin thickens and the hair falls out. Eventually the area becomes an ugly mass with a wound in the middle. Sometimes, inflammation will extend all the way to the underlying bone causing a periosteal reaction. These patients often walk with a limp.
Unfortunately, the cause of the condition is not completely understood. It appears to be caused by a combination of factors including the personality of the dog, an inciting cause then escalating damage from the constant licking. Lick granulomas are most common in anxious dogs who demonstrate obsessive/compulsive behavior. Although I was taught in veterinary college, that the anxiety causes the licking that causes the granuloma, I am not sure this is always true. I have seen calm, well-adjusted dogs become anxious after an injury to their leg. My impression is that they lick to relieve the pain. I have also seen really anxious, obsessive/compulsive dogs who do not develop lick granulomas after an injury.
Lick granulomas are usually located on the wrists and hocks. Possible inciting causes include trauma that causes bone or nerve injury, foreign bodies such as splinters or cactus thorns, allergies and mange. Whatever the initial cause may be, the actual damage comes from the chronic licking. The licking damages the skin and allows secondary bacterial and/or fungal infections to occur. The infections are very itchy making the patient lick even more.
Successful treatment requires diagnostic tests to determine the cause. My workup depends upon the severity of the granuloma and the patient’s history. I usually start out with blood work and a skin scrape to look for mites. If those tests are normal, I take x-rays of the area to look for an underlying orthopedic problem. Many patients require a surgical biopsy of the tissue for diagnosis. I combine this with a culture from deep within the granuloma to look for fungus and bacteria.
Multiple treatments are often required for acral lick dermatitis. Here are my recommendations:
1) Remove the underlying cause if possible. If the dog has a bone plate or pins, remove it. I have watched dogs with hardware inside their legs lick excessively when their legs get cold.
2) Treat the infection aggressively. Most of these dogs require 2-3 months of antibiotic or antifungal therapy to reach the deep seated infections.
3) Prevent licking. I personally do not like to bandage these wounds because it prevents the wound from drying out. Under a bandage, the wound stays moist and promotes microbial growth. If the dog will tolerate it, I put an e-collar on them. It is important to make sure the collar is long enough to prevent licking. )
4) Control the itch. This usually involves some sort of anti-inflammatory medication, usually a steroid. The steroid can be sprayed over the surface, injected into the mass or sometimes given orally. There is a new drug on the market called Apoquel that I have used for patients with severe allergies. I am eager to see if this works for granulomas. (More information on this drug can be found on my prior post at http://drnelsonsveterinaryblog.com/2014/02/20/apoquel-oclacitinib-maleate-for-treating-allergies-in-dogs.aspx)
5) Treat nerve pain. I think nerve pain is one of the most overlooked components of lick granulomas. To see if nerve pain is part of the problem, I will numb the area with a local anesthetic. If this works, I often place the dog on Gabapentin. I also give the owners a topical spray (Dermacool) that they can spray on the granuloma. It works great for the middle of the night, when the dog is uncomfortable and can’t sleep.
6) Use anti anxiety medications as needed. As I said before, I am not sure if anxiety caused the dog to lick or the dog became anxious because of the discomfort from the granuloma. I usually try my other treatments first to see if the dog needs something to calm it down.
7) There are many more treatments that have been tried for this frustrating problem including laser ablation, surgical removal, acupuncture, herbal therapy and medical laser.
Unless the cause can be found and removed, acral lick dermatitis usually becomes a chronic condition. Treatment calms it down but never cures it once a large granuloma is formed.