# What Causes Dog Warts? Types, Spread, and Treatment Most dog warts are caused by canine papillomaviruses, a family of viruses that infect the skin and mucous membranes. These viruses are common, and they usually produce benign, cauliflower-like growths that many dogs clear on their own. Not every lump that looks like a wart is one, so a veterinary exam matters. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Most true dog warts are viral papillomas caused by canine papillomavirus (CPV) types, and dogs are currently recognized as being infected by 25 different CPV types [1]. - Young dogs and dogs with weakened immune systems are most often affected, and oral papillomatosis is typically a benign condition that regresses on its own in most cases [2]. - Dog warts can be contagious between dogs through direct contact, shared bowls, toys, or grooming items, though they generally do not spread to people. - Many viral warts shrink and disappear without treatment, but warts that grow, bleed, multiply, or appear on the eyelids, claw beds, or inside the mouth should be checked by a veterinarian. - Any ongoing or growing skin abnormality on your dog should be examined by your veterinarian, because early diagnosis offers the best chance for effective treatment [3]. ## What Dog Warts Actually Are A wart is a small, usually raised growth on the skin or a mucous membrane. In dogs, the classic wart is a papilloma, which is a benign outgrowth of skin cells triggered by a papillomavirus infection. The surface often looks like a tiny cauliflower or a cluster of thin finger-like projections. Papillomas can appear almost anywhere. They show up on the lips, inside the mouth, on the eyelids, around the nose, on the paws, and on the belly. One report described a claw bed inverted squamous papilloma that showed up simply as a swollen digit, which is a good reminder that warts do not always look like warts [4]. It helps to separate two broad groups. Viral papillomas are caused by papillomavirus infection. Other skin growths, including sebaceous adenomas, histiocytomas, mast cell tumors, and various cysts, can look similar to a wart but have completely different causes and behavior. A veterinarian cannot always tell them apart by eye alone. Skin problems in dogs are often described first as dermatitis, which is a general word for any inflammation of the skin and is used until a specific diagnosis is reached [5]. That is why a wart-like lump gets a name only after an exam and sometimes a lab test. If you want a deeper clinical overview of these growths, see [Warts On Dogs: Comprehensive Veterinary Reference Guide](/knowledge/veterinary-medicine/dermatology/warts-on-dogs). ## Signs Owners Notice Most owners spot a wart before they know what it is. Common things you may see include: - A small, firm, raised bump with a rough or cauliflower-like surface - Clusters of bumps, especially around the mouth or eyes - Drooling, dropping food, or reluctance to chew if warts are inside the mouth - Paw licking or limping if a growth is on a digit or claw bed - Bleeding or crusting if a wart is bumped, scratched, or rubbed Skin inflammation in dogs can show up as itching, scaling, redness, thickening, darkening, oily coat, odor, or hair loss [5]. A wart itself is usually not itchy, so if your dog is scratching a lot, something else may be going on. Itching has many causes, and you can read more in [Why Is My Dog So Itchy?](/knowledge/veterinary-medicine/parasitic-diseases/why-is-my-dog-so-itchy). ## What Causes Dog Warts? ### Papillomavirus in Dogs Canine papillomaviruses are the main cause of viral warts. These viruses infect the outer layers of skin and mucous membranes and push cells to multiply, which creates the visible growth. Dogs are currently recognized as being infected by 25 different CPV types, and a newer type, CPV26, was identified within the Omegapapillomavirus genus [1]. Different CPV types tend to cause warts in different places. Canine papilloma virus 1 is the type linked to canine oral papillomatosis, the classic mouth warts seen in young dogs [2]. Canine papillomavirus type 2 has been linked to a claw bed inverted squamous papilloma, meaning some paw and nail bed growths are viral in origin [4]. ### Why Does My Dog Have Warts? Exposure is the short answer. A dog picks up papillomavirus through contact with an infected dog or with contaminated objects. Once the virus enters small breaks in the skin or mucous membranes, it can take weeks to months before a wart appears. Age and immune status matter a lot. Oral papillomatosis primarily affects young or immunosuppressed dogs [2]. A young dog with a developing immune system often gets warts and then clears them. An older dog with a new wart-like growth deserves closer attention, because the immune system is less likely to be the whole story. ### Are Dog Warts Contagious? Dog warts are contagious between dogs, especially among dogs in close contact. That includes multi-dog households, boarding facilities, daycare, dog parks, and shelters. The virus spreads through direct nose-to-nose or mouth contact, and shared food bowls, water bowls, toys, and grooming tools can also carry it. The good news is that canine papillomaviruses are not considered a risk to people. A person cannot catch a dog wart from their dog. If a human family member has warts, those come from human papillomavirus types, which are different viruses. ### Risk Factors - Young age, especially puppies and dogs under two years - A weakened or immature immune system - Living with or regularly meeting many other dogs - Sharing bowls, toys, bedding, or grooming equipment - Existing skin damage, which gives the virus an entry point Other conditions can also change the skin and make it look abnormal. Hypothyroidism can cause dry, scaly, thickened skin with hair loss, and Cushing disease can cause darkening of the skin, hair loss, oily dandruff, calcium deposits, and secondary bacterial infection [3]. These are not warts, but they can be confused with skin growths at a glance. ## How Veterinarians Diagnose Warts Diagnosis starts with a hands-on exam. Your veterinarian will look at the number, location, size, and surface of the growths, then check the rest of the skin and the mouth. They will also ask about your dog's age, other dogs in the home, and how long the growths have been present. For a typical cluster of mouth warts in a young dog, the appearance alone may be enough. For a single lump, a lump in an unusual spot, or a growth in an older dog, more testing is often needed. Options include: - Fine needle aspiration, where cells are collected with a thin needle and examined - Biopsy, where a piece of the growth is removed and sent to a lab - PCR testing, which can detect papillomavirus DNA in the tissue PCR and similar molecular tests are how specific CPV types get identified. In the claw bed case, CPV type 2 was amplified by PCR and localized to the papilloma's epidermis using in situ hybridization [4]. That level of testing is not needed for every wart, but it can help when the diagnosis is unclear. A useful rule: any ongoing or growing abnormality of the skin should be examined by your veterinarian [3]. A wart that has been stable for months is different from a lump that doubled in size in two weeks. ## Treatment Options for Dog Warts | Situation | Typical approach | |---|---| | Young dog with classic oral warts, eating and breathing normally | Monitor and let the immune system work, since most cases regress spontaneously [2] | | Warts causing discomfort, bleeding, or trouble eating | Veterinary treatment, which may include surgery or topical therapy | | Severe or recurrent oral papillomatosis | Surgical excision, sometimes with an added topical treatment to reduce recurrence [2] | | A single wart-like lump of unknown type | Sampling or removal, then lab evaluation | | Warts on eyelids, claw beds, or other sensitive spots | Prompt veterinary assessment, because location affects risk | ### Watchful Waiting Many viral warts do not need treatment. Canine oral papillomatosis is a benign condition, and most cases regress spontaneously [2]. Your veterinarian may recommend monitoring if your dog is comfortable, eating well, and the warts are not in a dangerous location. ### Surgical Removal Surgery is an option when warts are large, numerous, or causing problems. One limitation is that surgical excision of oral papillomas carries a high risk of recurrence, which is why veterinarians sometimes add a second treatment at the same time [2]. ### Topical Treatments Topical therapies are an active area of veterinary medicine. In one case, a dog with severe oral papilloma was managed with surgical excision followed by topical mitomycin C, and the treatment prevented recurrence over a one-year period [2]. In another case, a two-year-old dog with an oral papilloma had nearly complete regression within three weeks of twice-daily application of molecular iodine, with complete mucosal healing at four weeks and no recurrence after one and a half years [6]. These are individual case reports, not standard protocols for every dog. If your veterinarian recommends a topical treatment, they will choose the product and calculate the dose based on your dog's weight, the location of the warts, and your dog's overall health. Never apply a human wart product or any iodine preparation to your dog without veterinary guidance, because some products are irritating or toxic when licked. ### Treating the Skin Around the Warts If the skin around the growths is inflamed or infected, that needs care too. Dermatitis has many causes, including irritants, burns, allergens, trauma, and bacterial, viral, parasitic, or fungal infection [5]. Treating a secondary skin infection can make your dog far more comfortable while the warts resolve. For more on that topic, see [Dog skin infection causes diagnosis treatment prevention](/knowledge/veterinary-medicine/dermatology-and-allergy/dog-skin-infection). ## Recovery, Outlook, and Long-Term Management The outlook for viral papillomas is generally good. Most young dogs clear oral warts on their own, and the growths often disappear over weeks to a few months. Some dogs get a second round before their immune system settles, and a small number develop persistent or widespread warts that need treatment. After treatment, your veterinarian will likely want a recheck to confirm healing and to watch for new growths. Recurrence is possible, especially with surgical removal of oral papillomas [2]. If warts keep coming back, your veterinarian may look for an underlying reason, such as an immune problem or another skin disease. Long-term management is mostly about monitoring. Take a photo of any new lump with a ruler or coin next to it for scale. Check the size monthly. Note any change in color, surface, or bleeding. Bring that record to your next visit. If your dog has a growth that has broken open or will not heal, that is a different problem than a simple wart. See [Dog Skin Ulcers: Causes, Treatment, and When to See a Vet](/knowledge/veterinary-medicine/dermatology/skin-ulcer-dog) for more on non-healing skin wounds. ## Prevention You cannot fully prevent papillomavirus exposure, but you can lower the odds and limit spread. - Keep dogs with active warts away from daycare, boarding, shows, and dog parks until the growths resolve. - Do not share bowls, toys, bedding, or grooming tools between a dog with warts and other dogs. - Wash shared items with soap and hot water, and let them dry fully. - Check your dog's mouth, paws, and skin regularly, especially after time around other dogs. - Keep your dog's overall health in good shape, since a strong immune system helps clear the virus. There is no vaccine in routine use for canine papillomavirus in the United States, so management focuses on reducing contact and monitoring. If your dog has a skin rash on the paws that you are not sure about, see [Dog Skin Rash on Paws: Causes and Treatment](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/dog-skin-rash-on-paws-causes). ## Limitations and When to Contact a Veterinarian This article covers general information only. Your dog's individual case needs a veterinarian who can examine the growths, ask about your dog's history, and decide whether testing or treatment is needed. Contact your veterinarian the same day if you notice: - A wart or lump that has grown quickly over days to weeks - Bleeding, oozing, or an open sore that will not heal - Warts inside the mouth that interfere with eating, drinking, or breathing - A growth on the eyelid or near the eye - A growth on a claw bed with swelling, limping, or nail changes - Many new warts appearing at once in an adult or older dog Go to an emergency clinic now if your dog is struggling to breathe, has heavy bleeding from a growth, cannot swallow, or seems painful and distressed. Schedule a routine visit if you find a new lump and your dog is otherwise comfortable. Early diagnosis of disease offers the best chance for effective treatment [3]. ## Frequently Asked Questions ### Are dog warts contagious to humans? No, canine papillomaviruses are not considered contagious to people. The viruses that cause warts in dogs are different from the human papillomavirus types that cause warts in humans. You can handle your dog normally, though washing your hands after touching an open or bleeding growth is still sensible. ### Will my dog's warts go away without treatment? Often, yes. Canine oral papillomatosis is a benign condition, and most cases regress spontaneously as the immune system responds [2]. Some dogs need treatment if the warts are severe, widespread, or causing discomfort, so let your veterinarian guide the decision. ### Can my dog give warts to my other dog? Yes, dog warts spread between dogs through direct contact and shared items like bowls, toys, and grooming tools. Keep an affected dog separated from other dogs until the growths clear, and wash shared items thoroughly. Dogs in the same household are at the highest risk because they share space and supplies. ### Do warts on dogs hurt? Most warts are not painful on their own. They can become painful or irritating when they are in a spot that gets rubbed, such as a paw, eyelid, or inside the mouth. If your dog is limping, pawing at the face, or reluctant to eat, the wart may be causing a problem that needs veterinary care. ### Can a wart-like lump on my dog be cancer? Yes, some lumps that look like warts are not warts at all. Skin growths in dogs can be benign or malignant, and a veterinarian often needs a sample to tell the difference. Any ongoing or growing skin abnormality should be examined, because early diagnosis gives the best chance for effective treatment [3]. ## Related Articles - [Warts On Dogs: Comprehensive Veterinary Reference Guide](/knowledge/veterinary-medicine/dermatology/warts-on-dogs) - [Dog skin infection causes diagnosis treatment prevention](/knowledge/veterinary-medicine/dermatology-and-allergy/dog-skin-infection) - [Why Is My Dog So Itchy?](/knowledge/veterinary-medicine/parasitic-diseases/why-is-my-dog-so-itchy) - [Dog Skin Ulcers: Causes, Treatment, and When to See a Vet](/knowledge/veterinary-medicine/dermatology/skin-ulcer-dog) - [Dog Skin Rash on Paws: Causes and Treatment](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/dog-skin-rash-on-paws-causes) - [Types Of Dog Ear Infections](/knowledge/veterinary-medicine/clinical-methods/types-of-dog-ear-infections) - [Dog Skin Sores: Causes, Home Care, and When to See a Vet](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/dog-skin-sores) - [What Causes Dog Dermatitis and Skin Irritation?](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/dog-dermatitis-causes) - [Red and Itchy Dog Skin: Causes and How to Soothe It](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/dog-skin-red-itchy) ## References 1. [Canis Familiaris Papillomavirus Type 26: A Novel Papillomavirus of Dogs and the First Canine Papillomavirus within the Omegapapillomavirus Genus](https://pubmed.ncbi.nlm.nih.gov/38675936/). Viruses, 2024. 2. [Topical Mitomycin C Application Following Surgical Excision in Canine Oral Papilloma: A Case Report](https://pubmed.ncbi.nlm.nih.gov/40509947/). Veterinary medicine and science, 2025. 3. [Whole-body Disorders that Affect the Skin in Dogs - Dog Owners](https://www.merckvetmanual.com/dog-owners/skin-disorders-of-dogs/whole-body-disorders-that-affect-the-skin-in-dogs). Merck Veterinary Manual. 4. [Claw bed inverted squamous papilloma associated with canine papillomavirus type 2 in a dog](https://pubmed.ncbi.nlm.nih.gov/37779201/). Veterinary dermatology, 2024. 5. [Dermatitis and Dermatologic Problems in Dogs - Dog Owners](https://www.merckvetmanual.com/dog-owners/skin-disorders-of-dogs/dermatitis-and-dermatologic-problems-in-dogs). Merck Veterinary Manual. 6. [Treatment of a Canine Oral Papilloma With Topical Molecular Iodine: A Case Report With Implications for Antiviral Therapy in Humans](https://pubmed.ncbi.nlm.nih.gov/41220439/). Cureus, 2025. ## Further Reading - [Merck Veterinary Manual: Dog Owners](https://www.merckvetmanual.com/dog-owners) - [Cornell Richard P. Riney Canine Health Center: Canine Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)