Lick Granuloma (Acral lick dermatitis or ALD) in Dogs
Clinical Presentation Raised, ulcerated firm masses are seen, most often on the cranial carpus. Chronic lesions become hard and thick. Peripheral hyperpigmentation is common. Arthritis may be associated with long- standing lesions.
Diagnosis of Lick Granulomas in Dogs
In any case of lick granuloma, diagnosis should include deep skin scraping to rule out demodicosis and fungal culture to rule out dermatophytosis. It is important to note that deep skin scrapings may be falsely negative in areas that are excessively fibrotic and biopsies may be necessary to rule out demodicosis. Biopsy for histopathology and culture should also be taken to rule out fungal infections, pythiosis, neoplasia (cancer) and to identify the bacteria responsible for the infection (Pseudomonas is often present together with Staphylococcus). Pythiosis is a potentially lethal subcutaneous fungal disease common in Southeastern United States. It is caused by an alga present in standing water and dogs become infected swimming in infected areas. It has a predilection for German shepherds and Labrador retrievers and is intensely pruritic and rapidly progressive. If the animal has a history of living in endemic areas for pythiosis, a biopsy for histopathology and culture should be taken as soon as signs compatible with a lick granuloma are observed. Failure to make an early diagnosis may result in the animal’s death due to the fact that the only possible treatment at the present time is aggressive surgery. Biopsy of true cases of lick granuloma reveals marked epidermal hyperplasia and dermal fibrosis. It is common to see folliculitis, or inflammation of the hair follicle, and furunculosis, which is a ruptured hair follicle, with secondary bacterial infection.
Treatment of Lick Granulomas in Dogs
As you will read – this is a complex problem with no one logical or complete cure. Many therapies are recommended, often together, to try to eliminate or minimize the problem. A course of antibiotics should always be prescribed to treat the concurrent infection. Marked decrease of pruritus is seen in most cases after antibiotic therapy. As this is a deep infection, antibiotics should be continued for at least two months. Some cases have a mixed bacterial infection, so therapy should be based on culture and sensitivity. Good empirical choices include cephalosporin (cephalexin) and fluoroquinolone (enrofloxacin). As a general rule antibiotic therapy should be continued for a month past resolution of clinical signs. It is not uncommon for an antibiotics course to be at least 4 months. It is very important to try to identify the possible underlying disease for lick granulomas, as there is usually a cause. Veterinarians reserve symptomatic treatment for only truly idiopathic cases. Your veterinarian will want to spend time with you and identify any possible factor that might have triggered the condition, including the presence of a new dog, cat or baby in the house, a change in work schedule, death of another pet in the house. Special effort should be made to correct any possible stressful factor and change the lifestyle of the animal so that more time is spent exercising and playing. Immunotherapy to address allergies may be recommended. Drug therapy using cyclosporine (Atopic®) has been beneficial in some dogs.
Several drugs can be used for the symptomatic therapy for lick granulomas. They should be used only for a short period of time to break the cycle. They include: Clomipramine (Anafranil®, Clomicalm®) is an antidepressant with serotonin re-uptake inhibitor properties. Fluoxetine (Prozac®) is a bicyclic antidepressant that is a specific and potent inhibitor of the presynaptic re-uptake of serotonin. It has essentially no effect on the re-uptake of norepinephrine or other neurotransmitters. It is well absorbed after oral administration with absolute bioavailability in dogs of approximately 70 percent. After a single dose, the elimination half-life is one to three days. After long-term administration, the elimination half-life averages four days. Little is known about potential drug interactions; however, fluoxetine appears to have minimal clinically relevant interactions. Fluoxetine has been used with success in obsessive-compulsive disorders like lick granulomas. Significant efficacy was confirmed in a placebo-controlled study. The frequency of side effects is low and dose related; the most common effects are nausea, anxiety, insomnia, anorexia, diarrhea and nervousness. Amitryptiline (Elavil®) is a tricyclic antidepressant with strong antihistamine (H1 blocker) properties. It is useful to decrease pruritus in dogs in which the licking has both an allergic and a psychologic component. Full efficacy is reached after three to four weeks of therapy. As dogs become addicted to this medication it is important to taper it slowly when discontinuation is necessary to avoid severe re-bound effects. Naltrexone (Trexan®) or Naloxone (Narcan®) is a narcotic antagonist used successfully for the treatment of lick granulomas. Relapse of lesions is common after discontinuation of therapy. Adverse effects are not common and include drowsiness, and withdrawal from owner. They resolve after stopping the drug. This drug is quite expensive. Hydrocodone(Hycodan®) is an opiate that could be useful in some cases. The rationale is to provide an external source of endorphins in order to decrease the urge of licking. Cough medications such as Dextromethorphan is also used to help break the itch cycle by interfering with opioid receptors. Drugs for pain that have been used with some success include Tramadol (Ultram®) and gabapentin (Neurotin®). Arthtritis should be treated with appropriate drugs such as non-sterioidal anti-inflammatory drugs or glucosamine chondroitin.
Topical Therapy OptionsTopical therapy may help in some cases: Mechanical barriers such as socks, bandages, or Elizabethan collars are sometimes useful to minimize exposure to the area. Topical medications or liquids to act as a deterrent are used such as Yuk® Anti-lick Gel, Bitter Yuk!, Grannick’s Bitter Apple or Grannick’s Bitter Apple + Liquid Heat. Capsaicin (0.25 percent) works by triggering the release of Substance P (a neuropeptide involved in the transmission of pain and itch). After repetitive use the skin is depleted of Substance P thus itch and pain are not perceived any longer. It could be applied alone or in combination with other compounds like Bitter Apple® to create a bad taste. It should be applied twice or three times daily at the beginning of the treatment. Frequency of administration may be increased once improvement is obtained. Capsaicin is available over the counter. Initial and temporary worsening may be seen in some cases. The product should not be applied on ulcerated areas but around the lick granuloma to avoid a burning sensation. Sensitization may occur with prolonged used. Relief persists for several weeks after discontinuation of therapy as it takes several weeks to replenish the storage of Substance P in the skin. Combination of fluorinated steroids (e.g. Synotic®) and flunixin meglumine (Banamine®) may also be helpful. Solution should be applied twice daily initially until healing is observed. Intralesional injections of glucocorticoids (Vetalog®) (Depo-Medrol®) may be useful in small early lesions but are usually without any benefit in more chronic and ulcerated lesions. Cryotherapy, radiation therapy, and surgical removal are last resort options that could be attempted if everything else has failed.