Overview of Canine Lick Granuloma
Lick granuloma, also kown as acral lick dermatitis (ALD), Acral Lick Granuloma (ALG) or Acral Lick Furunculosis (ALF), is a common condition observed in large, active dogs in which the dog licks an area excessively, usually on the front leg, until a raised, firm ulcerated lesion is formed. These lesions are prone to infections, which make them itchier and itchier, which then leads to a self-perpetuating cycle of itching and licking. The term “acral” refers to the peripheral portion of an extremity.
Many underlying diseases are responsible for this condition. It could be caused by psychological and behavioral factor or by skin and internal diseases. Allergies, endocrine disease, parasitic, bacterial and fungal diseases may cause lick granulomas. Interestingly, allergy to flea bites may also be a cause. Aggressive flea control is recommended in flea-sensitive individuals. In other cases, a change in the environment, a stressful situation or a change in the work schedule of the owner could be the trigger.
Sometimes the granuloma occurs in an area of a previous trauma like a fracture and that may be triggered by an abnormal sensation in the skin. In other cases, the excessive licking may be a sign of pain. Arthritis may be evident in the underlying joint.
It is important that the underlying case is identified and addressed in order to resolve this frustrating condition.
Diagnosis of Lick Granuloma in Dogs
Diagnostic tests are necessary to confirm a diagnosis of lick granuloma and investigate the underlying cause in dogs. Tests may include:
Deep skin scrapings and fungal cultures are necessary in all cases.
Skin biopsies and cultures of the affected tissue are also important tests, because most of these lesions are infected and it is important to identify the organism responsible for the infection and establish an effective therapy.
Treatment of Lick Granuloma in Dogs
Treatment of canine lick granulomas may include:
If a psychological component is identified it is important that all efforts are made to correct the problem. In some cases, the death of a pet may trigger the problem. In those cases it may be useful to introduce another pet in the house so that the affected animal has a playmate and is distracted, especially when the owner is not at home.
It is important to allocate enough time for exercise and playing especially in large breed dogs, which are very active. Long walks are always very helpful. If the cause is the introduction of another pet or the arrival of a baby in the house, it is important to pay more attention to the older animal so that he/she does not feel left out.
As most lesions are secondarily infected you will need to administer an antibiotic for a prolonged period of time, usually 2-3 months. Infections are usually very deep and it takes some time before the are completely resolved.
Symptomatic therapy could be tried to discourage the licking. That includes the use of systemic and topical medications. Systemic medications are usually antidepressant or anti-anxiety drugs. It is important that these medications are considered as a substitute for the identification of the underlying cause. They should be used for a short period of time to help break the cycle. They have the potential of causing serious adverse effects and they are quite expensive. A prescription is required for these medications.
The safest topical therapy that could be tried on these lesions is capsaicin (0.25 percent). It is available as an over the counter product in drug stores, as treatment for pain and pruritus (itching) in people. It works by depleting the skin of the molecules responsible for the transmission of these sensations. It should be applied 2-3 times daily for a few weeks before improvement is noted. Some individuals may build sensitivity to this medication thus if worsening is noted, this therapy should be discontinued.
Lotions with a bitter taste are usually not strong enough to prevent licking. Elizabethan collars may be necessary to reduce licking while the medications are allowed take effect.
In-Depth Information on Lick Granuloma in Dogs
This condition is also called Acral Lick Dermatitis (ALD). Large breed dogs are predisposed including Doberman Pinschers, Great Danes, golden retrievers, Irish setters, Labrador retrievers, German short-haired pointers,Weimmaraners, shar peis, boxers and German shepherds. It seems to be more common in males (2:1 ratio), and it can start at any age, but most dogs are middle age or older (most > 5 years of age).
Carpal (wrist) or metacarpal areas are the most common sites. Possible underlying causes for lick granulomas are hypersensitivities to inhalants, food and fleas, demodicosis, hypothyroidism, dermatophytosis, pre-existing wounds or trauma, joint disease, staphylococcal pyoderma never properly addressed, psychogenic and neurogenic.
Boredom may be a significant factor to trigger the habit of licking, especially in large, active dogs. Lick granulomas are almost always secondarily infected at the time of presentation and the infection contributes to the pruritus thus a vicious cycle is created.
It has been reported that up to 70% of dogs with ALD have concurrent anxiety or fear based behavioral problems. These include separation anxiety and noise phobias)
Excessive licking may trigger the release of endorphins, which may have an analgesic effect thus raising the threshold of pain.
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 Options
Topical 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.
Because of the possible boredom component to this disease, it is a good idea for dogs with this disease to also have daily play and exercise. Socialization and play with other dogs is sometimes beneficial. Providing both individual and group attention in multi-dog homes is important.
Follow-up for Lick Granulomas in Dogs
Boredom can be prevented by allowing plenty of exercise, especially in large breed dogs. Once lick granuloma has started, aggressive antibiotic therapy is recommended. In some cases this condition is related to flea allergy, thus flea control may prevent this condition.