There are relatively few things that can cause bumps on the lips of your dog. Most are benign and easily treatable, but bumps on your older dog’s lips is a cause for concern. This article covers the symptoms, causes, diagnostic tests, treatment, and prevention of bumps on your dog’s lips.
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Bumps on Dog Lips
Papilloma virus (warts)
Dog warts are probably the most common cause of a bump on the lips of your dog. “Warts” are essentially benign (non-cancerous) skin tumors caused by canine papilloma virus-1 (CPV-1). These tumors have a classic fimbriated appearance, which means they are round, but have a rough surface similar to a sea anemone or a cauliflower. They typically occur on the lips and around the muzzle of a young dog (usually less than two years of age). Rarely, these papillomas can be found on the eyelids or between the toes. They are usually found in groups, so if you find one on your dog, continue looking inside his mouth and around his lips for more papillomas.
The virus is transmitted by direct contact with the papillomas of an infected dog or with the virus itself in an infected dog’s environment (toys, bedding, food bowls, etc.). Because the actively dividing cells that the virus prefers are deep within the skin layer, the virus must infect a new dog through injured skin; dogs with healthy intact skin will not become infected. The incubation period (time between infection and onset of symptoms) is one to two months.
Once a dog has been infected, the viruses insert their DNA into the dog’s cells and take over control of the cell division process, causing the skin cells to divide abnormally and more often than normal. The virus also prevents the normal process of programmed cell death. Thus once the virus establishes itself, there is a rapid and abnormal growth of skin cells that results in the formation of “warts” or papillomas.
Normally a mature immune system is able to combat the virus before it takes hold, but young dogs who do not have a fully developed immune system are susceptible to the virus. Senior dogs with weaker immune systems due to age and those dogs whose immune systems are compromised due to steroid use or chemotherapy, may also be susceptible to the canine papilloma virus.
Diagnosis of oral papillomas is usually fairly straightforward since they have a rather unique and characteristic appearance.
Treatment is usually not necessary in younger dogs since most papillomas will spontaneously disappear within 1-2 months as the developing immune system learns how to deal with the virus. However, senior or immunocompromised dogs are more likely to have papillomas that persist for more than a few months, or are more likely to have their papillomas develop into malignant squamous cell carcinomas.
In some cases, oral papillomas may be infected with bacteria from the mouth. If that is the case, oral antibiotics will be prescribed to clear the bacterial infection.
For those dogs whose papillomas persist for more than three months, or whose papillomas interfere with the dog’s normal function (especially eating), or if there are concerns about the possibility of conversion to cancer, surgical removal is recommended. Cryotherapy, the removal of the “warts” by freezing the tissue, is also a possible treatment in some specialty clinics.
Other treatments that could potentially be used earlier on in the disease process include azithromycin, interferon, and imiquimod. Azithromycin is an antibiotic that seems to have some action against various viruses via an unknown mechanism. In 2008, it was reported that a 10-day course of azithromycin removed all oral papillomas within 15 days. Later clinical trials by other groups yielded mixed results, but since the drug is relatively inexpensive and readily available, it’s reasonable to try azithromycin therapy, particularly in more severe cases.
Interferon is a cell signaling molecule produced by the body that has several important roles in the body’s defense against viruses. Injections of interferon have been used in humans for HPV infections, with mixed results. While there have been a few promising reports of interferon use in dogs, there have not been any controlled experiments demonstrating its effectiveness, nor any studies regarding its safety in dogs. Interferon therapy should be considered experimental.
Imiquimod is a drug that enhances the immune response. It is a topical cream that is used to treat genital warts and skin cancer in humans. Imiquimod has been shown to have some efficacy against dog papillomas. Often when using this drug, the skin is irritated around the papillomas, but this is considered a sign that the drug is working to speed up regression of the tumors.
Another possible treatment is creating a crude vaccine using the dog’s own tumors. Some of the warts are removed and used to create the therapeutic vaccine, which is then administered to the dog. The vaccine is thought to stimulate the dog’s own immune system to remove the rest of the tumors. Unfortunately, malignant tumors have been reported to develop at the vaccine injection site in some dogs.
A preventative vaccine against canine oral papillomas has been developed using recombinant DNA technology. While still considered experimental, the vaccine has been shown to be effective in preventing the development of oral papillomas.
Otherwise, prevention of viral papillomas consists of not allowing your dog to play with dogs that have visible papillomas. You should also prevent your dog from playing with the infected dog’s toys, or using his bowls or bedding. If your dog has wounds or rashes that compromise the integrity of his skin, it’s best to keep him away from places where other dogs congregate, such as dog parks or doggy day care. And if your dog does develop papillomas, keep him away from other dogs until the tumors regress.
Once your dog has recovered from the viral papillomas, he is then immune to reinfection of the same specific virus (but may be susceptible to other papilloma viruses).
Canine acne
Yes, just like humans, dogs can get acne. Canine acne is an inflammatory disorder of the lips, chin, and muzzle that results in the formation of blackheads, whiteheads, and raised, red lumps. More severe cases can lead to generalized swelling of the lips and muzzle with bleeding wounds or scabbing.
The exact cause of canine acne is uncertain, though it appears genetics play a role, as there are several breeds with predisposition to acne, including boxers, English bulldogs, German short-haired pointers, doberman pinschers, rottweilers, and mastiffs. Other than genetics, it is thought that most cases are related to trauma leading to rupture of hair follicles with subsequent release of the material inside the follicle. This material irritates surrounding hair follicles, which creates more inflammation. In some cases, acne may be related to food or environmental allergies.
Canine acne has a characteristic appearance which makes diagnosis fairly easy based on physical examination alone. However, a skin scraping may be performed to rule out demodectic mange, or a skin cytology may be necessary to rule out bacterial infection. If bacteria are found, then a culture and sensitivity test may be recommended to determine the exact bacteria causing the infection and the best choice of antibiotic to treat the infection.
The most common treatment of canine acne is topical benzoyl peroxide, which can be purchased over the counter or from your veterinarian’s office. Benzoyl peroxide helps flush out the hair follicles and reduce any bacterial contamination. Sometimes either topical or oral steroids may be used to help reduce inflammation within the skin. If the acne lesions are infected, your veterinarian may prescribe a topical or oral antibiotic. If the acne is thought to be due to an environmental or food allergy, then treating the underlying allergy will also help with treating the acne.
There are a few things you can do at home to prevent canine acne, or prevent its recurrence. First, resist the temptation to squeeze or pop any blackheads or whiteheads – this increases the chance the hair follicles will rupture and lead to worsening inflammation. Second, since most acne is due to trauma, see if the source of the trauma can be determined. Possible sources of trauma include eating from a plastic bowl with rough edges, using the nose/muzzle to root around in the dirt, or scratching at the face. Third, keep your dog’s muzzle clean and dry by giving it a quick wipe after meal times, and if your dog has deep facial folds (boxer, bulldog, etc.), be sure to keep those skin folds clean and dry as well.
Malignant melanoma
Melanomas are the most common type of oral tumor in dogs and are very aggressive. Melanomas arise from cells called melanocytes, which are cells that produce pigment (generally black). These oral tumors often appear as pigmented masses on the lips or gums that start to ulcerate or bleed as they grow larger. However, they can also be non-pigmented, or pink in color, found on the palate, tongue, or inside the lips, or look more like a flat plaque versus a discrete mass. The lesions may appear fairly small on the outside, but typically extend deep into surrounding tissues, including the jaw bone. Symptoms include bad breath, drooling, panting, movement or loss of teeth, lack of appetite or difficulty eating, facial swelling, reluctance to be touched on the head, and swelling of the lymph nodes in the neck.
As with most cancers, there doesn’t appear to be a single cause for the development of these tumors, but genetics does seem to play a role. Breeds that are predisposed to oral melanomas include chow chows, schnauzers, cocker spaniels, golden retrievers, Gordon setters, and miniature poodles. Most dogs with oral melanoma are at least 10 years of age at the time of diagnosis.
A fine needle aspirate (FNA) or a biopsy is used for diagnosis. Fine needle aspiration involves removing some cells from the center of the mass with suction using a syringe and attached needle. The cells are then placed on a microscope slide, stained, and examined by a veterinary pathologist. The major drawback of this method however, is that it’s possible to miss suctioning some cells that are essential for a firm diagnosis. A biopsy is generally accepted as more likely to get a definitive diagnosis. With a biopsy, a section of the mass is removed and sent off to an outside laboratory for a veterinary pathologist to review. Another benefit of a biopsy is that the pathologist can predict how the tumor is likely to behave – whether it will be locally invasive or spread to other parts of the body (metastasize).
Because oral melanomas are malignant (cancerous), once a diagnosis of melanoma has been confirmed, additional testing should be completed in order to determine the extent of the cancer, otherwise known as staging. Radiographs of the chest, FNA sampling of lymph nodes, and sometimes an ultrasound of the abdomen are performed in order to determine if and where the cancer has spread. Unfortunately with melanoma, it has often spread by the time it is discovered.
The combination of physical exam, measurements of the mass, and staging tests can be very helpful in determining a prognosis. The prognosis is reported as a median survival time (MST), which represents the length of time at which half the dogs at that stage of cancer have died and half are still alive. Tumors less than ¾ of an inch in size without spread (stage I) have an MST of 15-18 months with surgery alone. Once a melanoma has reached ¾ of an inch in size or larger (stage II), the MST drops to about 6 months with surgery alone. Tumors larger than 1.5 inches or if the disease has spread to the lymph nodes (stage III) have an MST of 3-4 months with surgery alone. Cancer that has already spread to the lungs (stage IV) has the poorest survival time of just 1-2 months.
Surgical removal of the tumor is the standard treatment for melanoma. The goal is to remove as much of the tumor as possible; any tumor cells left behind will eventually regrow. When the tumor has infiltrated the jaw bone, removal of the affected jaw is necessary to remove the entire mass. If surgery is not an option due to the location of the tumor, or if surgery is not able to completely remove the tumor, radiation therapy is an option. Melanoma responds relatively well to radiation therapy, and only about six doses are needed. When radiation therapy is used in combination with surgery, about 70% of patients are disease-free at the primary tumor site one year later.
A melanoma vaccine, ONCEPT, is available at some specialty practices in the United States. ONCEPT was approved by the USDA in 2007 for use in stage II and stage III oral melanomas, and represents the first licensed therapeutic vaccine for cancer in either dogs or humans. The vaccine works by alerting your dog’s immune system to the presence of melanoma cancer cells by targeting a particular protein found in melanoma; your dog’s immune system should then help destroy the cancer cells. However, the vaccine was not tested in randomized clinical trials, which is the gold standard for approval by the FDA, and some recent research indicates no significant difference in survival time with the use of the vaccine.
Melanoma tends not to respond well to chemotherapy, so other options are usually tried first. Chemotherapy may be helpful once the disease has spread beyond the primary tumor site, such as in stage IV disease. A recent study using a combination of the chemotherapy drug carboplatin with the non-steroidal anti-inflammatory drug piroxicam increased the MST from 30 days to 119 days, but didn’t have a significant effect on survival time for other stages of disease.
Lip fold dermatitis
Lip fold dermatitis doesn’t usually cause distinct bumps on a dog’s lips, but instead causes redness, irritation, swelling, alopecia (hair loss), and discomfort. Lip fold dermatitis is typically seen in dogs with droopy upper lips and lower lip folds, such as Saint Bernards, spaniels, English bulldogs, and basset hounds. The upper lips trap moisture from the mouth against the lower lips, resulting in a perfect environment for overgrowth of the normal skin bacteria and yeast. The microbes produce toxins and breakdown products that cause irritation, inflammation, and breaks in the upper skin layer, leading to further penetration of the microbes into the skin, causing chronic infection and inflammation. The situation is made worse if the dog has poor oral hygiene, as the bacteria from oral disease gets into the lip folds and causes even more irritation and foul odor.
Diagnosis of lip fold dermatitis can usually be made based on clinical signs alone. The redness and irritation do not generally extend beyond the area of folded skin. The diagnosis can be supported by skin cytology. Skin cytology involves running a moist cotton swab along the area of irritation and into the skin fold, then rolling the swab onto a microscope slide. Examination of the sample under a microscope will reveal bacterial overgrowth.
Treatment of lip fold dermatitis starts with clipping any hair in the area, so that the hair does not continue to trap moisture and microbes. The lip folds will need to be cleaned once or twice daily to remove any debris and microbial overgrowths. A cleanser with no more than 5% benzoyl peroxide may be used for cleaning, or products such as [Mal-A-Ket wipes] or [KetoHex wipes] may be used. Your veterinarian may prescribe a daily application of a topical diaper rash cream to help keep the area dry and prevent further recurrence. In severe and/or chronic cases, surgical correction of deep lip folds (called a cheiloplasty) can provide a long-lasting remedy and may be the best option.
Take away message for bumps on dog’s lips
Most causes of bumps or inflammation of your dog’s lips are relatively benign and easily treatable, but oral melanoma is an aggressive cancer with a high rate of metastasis and relatively poor prognosis. Be sure to have your dog seen by your veterinarian if you are concerned about any lumps or bumps near your dog’s lips.