Acral Lick Dermatitis

Acral lick dermatitis, also known as a lick granuloma, holds an esteemed place in veterinary medicine as one of the most frustrating conditions we treat. While there are no ‘silver bullets’ for this condition, we will discuss various treatments and approaches that I have had success with.

There are a variety of triggers for the condition, but the result is the same: obsessive, repetitive licking of an area of skin, leading to infection and the characteristic skin lesion. The constant licking likely triggers endorphin release, leading to a natural ‘high’, thus perpetuating the behavior.

Clinical signs

We are all familiar with the classic clinical appearance; a raised, ulcerated granuloma typically on the top of the carpus or metacarpus, or less commonly the tarsus or metatarsus. The lesion initially starts small, but constant licking leads to lichenification, fibrosis, alopecia, furunculosis and ulceration.

There are breed predispositions, with Doberman pinschers, Labrador retrievers, golden retrievers, boxers, Weimaraners, German shepherd dogs and Irish setters being over-represented.

Causes

There are a variety of triggers for lick granulomas, including allergy, parasites (mites), arthritis, neuropathy, foreign body, previous trauma or injury, metabolic (hypothyroidism), or behavioral causes such as boredom, stress, or anxiety.
Regardless of the primary cause, infection is always a complicating factor, with one study finding deep bacterial infection in 94% of lick granulomas.

Diagnostics and Treatment

I recommend cytology and deep skin scrapes or hair pluckings to look for Demodex mites. Culture is indicated if antibiotics have been previously administered unsuccessfully. When culturing these lesions, clean the granuloma gently with sterile saline. Squeeze the lesion to express some of the deep exudate and culture this. Additional potential tests include radiographs, biopsy or blood work, and should be performed depending on the suspected primary cause in your patient.

It is imperative to use a combined approach when treating lick granulomas. Initially, I focus on infection and the behavioral component. Because of the deep infection, long courses of antibiotics are needed. Six to twelve weeks of antibiotics are often required, ideally based on culture. I always recommend an E-collar to mechanically block the dog from licking. Doggleggs are an alternative if the dog will not tolerate an E-collar. Lick-preventing liquids or creams are not typically effective.

While behavioral problems are not always the primary cause of these lesions, they are always a complicating factor. Behavior modification drugs such as fluoxetine or clomipramine are often started initially. If you suspect that allergy is contributing, Apoquel, Atopica, CADI or antihistamines such as hydroxyzine should be considered.

Surgical removal is not usually recommended, as the patient will simply form a new lick granuloma at the surgical site. Various other treatments that have been attempted include laser therapy, radiation therapy, or acupuncture, but these treatments have been limited by variable response rates.

In summary, I treat lick granulomas initially with long course of antibiotics, ideally based on culture, and E-collar application, often with behavioral modification drugs. A thorough search for the underlying cause should be performed. Remember, that although allergy is a potential trigger, it is unlikely if acral lick dermatitis is the sole manifestation of skin disease. While the disease is not life threatening, it is frustrating for clients. I give owners a guarded prognosis, as relapse is common. Likelihood of success is higher if treatment is started early!


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