Acral lick granuloma: stopping the itch-lick cycle

While acral lick granuloma is rarely a life-threatening condition, it's irritating for both the dog and owner. (kisscsanad/stock.adobe.com)

Acral lick granulomas (also known as acral lick dermatitis), typically seen on the front part of the lower leg in dogs, are lesions that develop as a result of chronic and compulsive licking. The term comes from the location (“acral,” or belonging to the extremities) and the cause (licking). Constant licking causes hair loss and erosion or ulceration of the superficial skin layers, leading to marked inflammation of the skin and focal infection.

Over time, the skin in the affected area becomes red, raised and thickened, and constant licking prevents healing. It is likely that the licking and inflammation also cause the area to be itchy, which leads to more licking and the dreaded itch-lick cycle. It is also thought that local nerves become damaged and constant licking releases endorphins, which act as pain relief and comfort for the animal.

Causes and clinical signs

Many factors can contribute to the development of acral lick granulomas (although in some cases no cause is determined):

Infections caused by bacteria, yeast or fungi

Allergies (e.g. flea, food, environment)

Ectoparasites (e.g. mites)

Neoplastic disease

Joint disease, arthritis or previous surgery/trauma

Foreign material (e.g. suture, grass awn, splinter)

Neuropathies (e.g. nerve tumors or entrapment)

Metabolic diseases (e.g. hypothyroidism or Cushing's disease)

Stress, boredom, separation anxiety

Obsessive-compulsive disorder.

When looking for clinical signs, keep in mind that acral lick granulomas are skin wounds typically located on the distal area of the front leg or hind leg of a dog. In rare cases, they can occur in the flank or at the base of the tail. Some dogs may have multiple lick granulomas at one time.

These lesions usually start out erythematous and crusty, progressing to thickened, alopecic plaques or nodules. The center of the lesion is often ulcerated, red and moist, or it may be covered by a scab. The skin may be hyperpigmented.

Which dogs are more likely to have lick granulomas?

Both males and females can have lick granulomas, but study results have been inconsistent. Some report a male predilection, some a female predilection and some no sex predilection at all. The median age is 4 years, although dogs can be affected at any age. Some commonly affected breeds include the Doberman pinscher, German shepherd, German short-haired pointer, golden retriever, Great Dane, Irish setter, Labrador retriever, Weimaraner and boxer.

Getting a diagnosis

Usually, a combination of the following steps will help diagnose acral lick granulomas.

Patient history. Some helpful questions to ask your veterinary clients:

• When did licking start?

• How often is licking noted (certain times of day or year, when pet is alone or in the presence of others)?

• Have there been any changes in the dog's environment or normal routine (e.g. moving, new baby or animal in household, loss of a family member)?

• Is there any history of trauma, pain or surgical procedures?

Physical exam. Refer to the clinical signs listed above to get the best picture possible for an accurate diagnosis.

Skin cytology. Squeezing the area to release exudate from the lesion, followed by an impression smear, can be helpful. In many cases, however, the sample is taken from areas that are too superficial and deeper cultures need to be performed.

Fine-needle aspiration. Nodular lesions may help rule out neoplastic disease.

Skin scrapings or trichograms. These are performed to rule out demodicosis.

Dermatophyte testing. A fungal culture or polymerase chain reaction will identify dermatophyte infection as an underlying cause.

Dermatohistopathology and skin culture. Obtaining a skin biopsy for dermatohistopathology testing will confirm a diagnosis and rule out some possible underlying causes. A skin culture will help in antibiotic selection. A tissue sample is typically more informative than a surface swab because a deep bacterial infection is almost always present in these lesions.

Radiography. With the support of an orthopedic exam and history, radiographs will help identify a possible orthopedic cause of licking.

Treatment and clinical management

Although difficult to cure, acral lick granulomas are usually manageable. Putting a stop to the itch-lick cycle is key. Because recurrence is common, treatment requires addressing the suspected cause of the lesion(s). Depending on the underlying disease, combination treatments are often required. Keep in mind that what works for one dog may not work for another, and there's no magic pill or shot that will resolve the lesion.

Antibiotics. The main concern with this condition is secondary bacterial folliculitis and furunculosis. Resolution often requires two to three months (or longer) of oral antibiotic therapy.

Anti-inflammatories. Topical, oral or injectable corticosteroids may be indicated to decrease the dog's desire to lick while the antibiotics are taking effect. Nonsteroidal anti-inflammatories are another option to decrease discomfort. Just be sure not to use steroids and nonsteroidals simultaneously or you may risk gastrointestinal ulceration. Topical steroids may also decrease inflammation. Synotic (Zoetis), which contains dimethyl sulfoxide (to help the steroid penetrate deeper tissue) and fluocinolone, can decrease mild to moderate inflammation.

Topical products and physical barriers. Bitter apple or capsaicin in topical products is often effective at curbing the itch. Bandages, shirts or sleeves, E-collars and muzzles may prevent the dog from licking the granuloma. Although a physical barrier is not a long-term solution, it can allow for other medications to take effect and time for the patient to forget about the lesion.

Surgical removal. This may be a solution if the lesion is small, but recurrence is a concern if the underlying cause is not identified or treated.

Behavioral modification. This can include the owner spending more time with the dog, getting the dog a companion, training classes, drug therapy (may include serotonin reuptake inhibitors such as fluoxetine and tricyclic antidepressants such as clomipramine) or consulting a specialist in animal behavior.

Other therapies. The use of CO2 laser and cold laser therapy have been reported to help in select cases. Acupuncture around the affected area also has been helpful in some cases.

For most patients, the prognosis is guarded. While acral lick granuloma is rarely a life-threatening condition, it is irritating for both the dog and owner. Client compliance is very important to resolving acral lick granulomas, so be sure to inform pet owners that treatment is a slow process that will likely take several months. Dogs that receive early treatment have a better prospect for recovery than dogs with chronic or severe conditions.

Dr. Judy Seltzer graduated from the Royal Veterinary College in London and completed her residency in dermatology at the University of Florida. She has been working in her home state of New York since 2009, currently at BluePearl Veterinary Partners in New York City. She and her husband have a baby girl and four cats and enjoy traveling, fall festivals, winter activities and dining out.