Warts (papillomas) are caused by papillomaviruses. In dogs they are very common, and many probably come and go without the owner ever noticing. [1] This guide covers how dogs get them, the kinds of warts vets see, why a vet should look at any wart-like growth, and what papillomavirus does in cats, where true warts are rare. For other growths, see lumps and bumps on dogs and lumps and bumps on cats.
How dogs get warts
The viruses that cause warts can pass from one animal to another directly or through shared objects. [2] The virus gets in through tiny scrapes and breaks in the skin or the lining of the mouth. [1][2] Outbreaks have been reported now and then where many dogs mix, such as doggie daycare. [1]
Warts usually appear when a dog meets the virus for the first time, which is why most are seen in young dogs, typically between 6 months and 2 years old. [1]
What warts look like
Warts are raised growths that stick out from the skin, and there are often several of them. Looked at closely, the surface is usually rough or made of small finger-like folds. [1] Because the virus enters through small injuries, the usual places are the mouth, the feet, and the face and ears. [1]
The kinds of warts in dogs
- Mouth (oral) warts. Several warts in the mouth of a young dog are the classic picture, and a vet can often recognise them on sight. [1] They rarely bother the dog, but large numbers can occasionally make eating difficult. [1]
- Skin warts. These look much the same as mouth warts and are caused by the same group of viruses. [1]
- Inverted papillomas. Instead of growing outward, the thickened skin folds inward and sits in a sunken, cup-shaped lump. This shape does not change how the wart behaves. [1]
Warts on the paws
North American vets sent in records of 44 dogs whose paw (pedal) papillomas were confirmed by biopsy. The typical dog was 4 years old, and the usual reason for the visit was limping, or licking or chewing at the paw. In 35 dogs the warts were on a single paw, and front feet were hit more often than hind feet. [3] For other paw problems, see dog paw problems.
Pigmented viral plaques
Papillomaviruses can also cause flat, dark patches called pigmented viral plaques. Unlike warts, they tend to appear in middle-aged dogs, and some breeds, especially Pugs and Vizslas, seem prone to them. [1] They usually start as several small, dark, slightly raised spots on the belly and the inner legs. [1] An Italian review of 55 such plaques found a typical age of 6.5 years, with pugs making up a quarter of the dogs and the belly and armpits as the usual places. [4] Most stay small and are only a cosmetic issue, but widespread plaques can itch or hurt. [1]
Many things look like warts
When a young dog has several typical warts in the mouth or on the skin, a vet can often tell what they are by looking. [1] A single growth, or one in an older dog, is a different matter. Other lumps can look similar, and the way to be sure is a biopsy, where a lab looks for the cell changes the virus causes. [1] This is one reason a vet should look at any new growth.
Do warts go away on their own?
Usually, yes. Once the dog’s immune system responds to the virus, the wart clears up. [1] How long that takes varies: most warts go within 3 to 6 months, but some last up to 2 years before they disappear. [1] A second review notes that most skin warts in dogs clear up by themselves within about 3 months. [2]
In the paw papilloma study, 34 papillomas resolved in total, and 25 of them resolved within 3 weeks after the biopsy was taken. Of the 21 dogs that received no additional treatment, 15 cases resolved. [3] In the pigmented viral plaque study, 3 cases went away without treatment. [4]
A small number of dogs keep growing new warts for many months, and the warts spread and get large. This seems to come from a weak immune response to this one virus, and these dogs usually show no other sign of a weak immune system. [1]
How vets treat warts
Since most warts heal on their own and seldom bother the dog, they are usually left alone. [1]
- Removing the wart. When a wart does need to go, for example because it gets in the way of eating or walking, the vet destroys the infected tissue, for example with surgery or freezing (cryotherapy). [1] Removal is expected to cure that wart, though new warts can still appear until the immune system catches up. [1]
- Medicines. No medicine has been proven to make warts go away faster. [1] Ask your vet before trying anything.
- Pigmented viral plaques. In the Italian study, single lesions did not come back after surgery, while the various medical treatments tried for multiple lesions did not work. [4]
Can warts turn into cancer?
Rarely. The evidence that papillomaviruses can cause a skin cancer called squamous cell carcinoma in dogs comes from the rare cases where pigmented plaques or long-lasting mouth warts turned into it. [1] For pigmented plaques this is generally considered rare, although almost 10% of plaques sent to one lab for diagnosis had progressed. [1]
A US diagnostic lab described 7 dogs whose harmless mouth warts went on to become squamous cell carcinoma, and its authors want vets to be aware this can happen. [5] In the Italian plaque study, 5 of the 55 plaques (9%) had a tumor growing beside them, and one dog with invasive squamous cell carcinoma was put to sleep. [4]
This is why a wart that keeps growing, changes, or does not go away is worth showing to your vet.
Is my dog contagious to other dogs?
Yes, the virus can spread between dogs by direct contact and through shared objects, and outbreaks have been seen where many dogs meet, such as daycare. [1][2] Ask your vet whether your dog should skip group play while warts are present.
Papillomavirus in cats
Cats are different. Cats rarely get true warts; only a handful of cases have been reported, such as small warts found by chance under the tongue or on the nose or eyelids. [1] Instead, papillomavirus in cats mainly causes viral plaques. The more advanced form used to be called Bowenoid in situ carcinoma (feline Bowen disease), but experts now treat both simply as viral plaques. [1]
What to know about viral plaques in cats: [1][6]
- They usually show up in middle-aged to older cats. [6]
- They look like several flat, slightly raised patches, dark or skin-coloured, up to about 2 cm across, most often on the face, head and neck. They are usually not painful or itchy. [6] Larger ones can become crusty. [1]
- Almost all cats carry the virus from around birth without any problem. Plaques seem to appear when the cat’s immune control of the virus slips, for reasons that are usually unknown. Most affected cats have no other immune disease. [1][6]
- Plaques in cats are more likely than in dogs to grow and spread and to turn into squamous cell carcinoma, especially in Devon Rex and Sphynx cats. [1]
- Treatment is aimed at the skin itself, for example surgery, laser or freezing. Surgery can cure a small number of plaques, but may not be possible when there are many. [1][6]
When to see your vet
- Any new growth. Many things look like warts, and only a vet’s tests can confirm what a growth is. [1]
- Warts in the mouth that make eating difficult. [1]
- Lameness or paw licking or chewing with a growth on the paw. [3]
- A wart that does not go away, keeps growing or changes, because in rare cases they can turn into squamous cell carcinoma. [1][5]
- A cat with dark or skin-coloured patches, especially on the face, head or neck. [1][6]
FAQ
Are warts on dogs dangerous?
Usually not. Most clear up by themselves, and only rarely do they turn into squamous cell carcinoma. [1] Because many things look like warts, have your vet check any new growth.
How long do dog warts last?
It varies. Most go within 3 to 6 months, but some last up to 2 years. [1] In one study of paw papillomas, 25 of the 34 that resolved did so within 3 weeks after biopsy. [3]
My cat has a wart. Is it the same as a dog wart?
Usually not. True warts are rare in cats; papillomavirus in cats mostly causes viral plaques, which can sometimes turn into cancer. [1] Have your vet look at any new growth on your cat.
The bottom line
Warts are caused by papillomaviruses and are very common in young dogs. [1] Most go away by themselves within months, and only rarely do they turn into squamous cell carcinoma. [1] Many things look like warts, so a vet should confirm what a growth is. [1] In cats, true warts are rare, and the virus mainly causes viral plaques that are worth showing to your vet. [1][6]
This article is for general information and is not a substitute for a veterinary exam. If you are worried about a growth on your pet, see your veterinarian.
Sources
- Munday JS, Knight CG. Papillomaviruses and papillomaviral disease in dogs and cats: a comprehensive review. Pathogens. 2024;13(12):1057. CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC11728566/
- Medeiros-Fonseca B, Faustino-Rocha AI, Medeiros R, Oliveira PA, Gil da Costa RM. Canine and feline papillomaviruses: an update. Front Vet Sci. 2023;10:1174673. CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC10229045/
- Gould AP, Coyner KS, Trimmer AM, Tater K, Rishniw M. Canine pedal papilloma identification and management: a retrospective series of 44 cases. Vet Dermatol. 2021;32(5):509-e141. PMID 34212427 (abstract). https://pubmed.ncbi.nlm.nih.gov/34212427/
- Orlandi M, Mazzei M, Albanese F, et al. Clinical, histopathological, and molecular characterization of canine pigmented viral plaques. Vet Pathol. 2023;60(6):857-864. PMID 37644783 (abstract). https://pubmed.ncbi.nlm.nih.gov/37644783/
- Thaiwong T, Sledge DG, Wise AG, Olstad K, Maes RK, Kiupel M. Malignant transformation of canine oral papillomavirus (CPV1)-associated papillomas in dogs: An emerging concern? Papillomavirus Res. 2018;6:83-89. PMID 30414951. https://pubmed.ncbi.nlm.nih.gov/30414951/
- Munday JS, Thomson NA. Papillomaviruses in domestic cats. Viruses. 2021;13(8):1664. CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC8402708/