Acral lick granuloma

Lick granulomas are moist, fleshy pink sores usually on a dog’s legs. They are caused by excessive licking at the site and are frequently caused by an underlying disease that needs to be properly diagnosed and treated. If you suspect that your dog has a lick granuloma you should seek veterinary advice as soon as possible.

A lick granuloma is a red, sore patch of skin caused by the trauma of your dog licking continuously at one site. Most lick granulomas occur at a site that is easy for the dog to access – the left foreleg is often chosen as it’s comfortable to reach when the dog is lying down.

Many lick granulomas are the expression of an underlying itchy disease but the itchiness tends to express itself in a focal rather than generalised manner. In other cases, the licking may be a manifestation of pain (e.g. arthritis in older dogs) and might have been triggered by some trauma in the area.

An initial stimulus causes the dog to start licking at the site, this leads to infection and scarring and the area itself then becomes itchy because of the damage that has already been done and so becomes self-perpetuating. Since most of dogs with lick granuloma have deep infections, they benefit from a prolonged course of antibiotics.

It is thought that the act of licking causes the release of endorphins (natural opiates which provide a sense of well-being) in the dog’s brain. The dog soon learns that licking brings about this pleasant feeling, and keeps on licking. As the process continues, a fleshy pink mass known as a ‘granuloma’ may develop at the site. The area will usually always be moist and may become particularly red and inflamed if infected.

In some cases, people living with the dog may notice excessive licking of the affected area. However, many dogs lick themselves only when the owner is not present.

In many cases the initiating factor is an allergy or infection (e.g. ringworm) that causes the skin to be itchy or painful. However in some dogs the initiating factor is minor when compared to the psychological element. Nervous and highly-strung dogs appear to be more likely to develop lick granulomas but it can also be seen in dogs that spend a long time alone or receive insufficient exercise or mental stimulation.

Because they take a long time to develop, lick granulomas are most often seen in middle-aged or older dogs. Large breed dogs seem to be predisposed to develop them. Since endocrine and metabolic diseases may also be an underlying cause (e.g. decreased function of the thyroid gland) and these diseases tend to occur in older large breed dogs, these patients are overrepresented. Dogs may start to lick a site because of an underlying problem (itchiness or soreness at the site) but over time the habit becomes engrained and the dog simply derives pleasure from the act of licking.

Lick granulomas have a typical appearance. However, it is possible for other conditions (particularly infections and tumours) to mimic this appearance and it is important to be sure that the sore is not a tumour before treating it as anything else.

There are many underlying causes for lick granulomas and your vet will want to rule out these because if an underlying cause is not treated the lick granuloma will keep recurring.

Proper identification of the underlying cause is crucial to the success of the therapy. If such cause is not identified, lick granulomas may be extremely difficult to resolve. Antibiotic therapy will be necessary to reduce infection in the tissue. Due to the depth of the infection it is common to use oral antibiotics for months.

All therapy will need to be continued for at least 4 weeks after all signs of the sore have resolved. Even if a granuloma can be completely resolved there is still a risk of it recurring once treatment is stopped. Some vets recommend creams to rub into the wound – those containing local anaesthetics may help to reduce the desire to lick. Application of aversives like bitter apple may also limit licking. Alternatively, drugs that interfere with the transmission of neuropeptides (important for the transmission of pain and itch) can be used. Capsaicin, the active ingredient of chilli pepper, can be used topically on the margin of the granuloma.

One of the reasons dogs continue to lick the site is that licking the sore area releases natural endorphins (morphine like substances) which make the dog feel good. In some dogs administration of an opioid drug, e.g. hydrocodone, can not only reduce irritation but may also fill the need for endorphins that the dog may be experiencing.

In really severe cases desperate measures such as surgical excision of the sore may be required. Surgical wounds at the site may not heal well either and if the dog starts licking at the stitches you may quickly be in a worse position than before surgery. You should think very carefully before embarking on this treatment and be sure you have discussed all the options with your vet.

Many dogs have underlying allergies or endocrine diseases that need to be addressed to ensure resolution of the existing granuloma as well as to prevent the recurrence. Additionally, addressing the potential psychological factors is important and some cases may respond to simple changes in environment (reducing stress or boredom). Reduction in boredom can be achieved by providing company for the dog, increasing exercise and training. In more difficult cases mood-altering, antidepressant drugs such as Prozac or amytriptiline have been advocated. There have been some reports of success with acupuncture.

Acral lick granulomas are extremely frustrating to treat. There is no simple cure and any success will only be achieved by a dedicated and consistent approach of both owner and vet.