Dogs get warts because of canine papillomavirus (CPV), a family of viruses that infect skin cells after slipping through tiny breaks or abrasions in the skin. The virus targets the deepest layer of skin cells following microtrauma, meaning even minor scratches, scrapes, or moisture-softened skin can create an entry point. Once inside, the virus hijacks cell growth and produces the fleshy, raised bumps we recognize as warts.
How Dogs Catch the Virus
Canine papillomavirus spreads through direct contact with an infected dog or with contaminated objects like shared toys, water bowls, and chew sticks. The virus needs a break in the skin’s surface to establish an infection. Activities that cause small injuries to the mouth or skin, like chewing sticks or rough play, make transmission easier because they damage the outer barrier and expose deeper cells to the virus.
The virus has an incubation period of one to two months, so warts don’t appear right away. A dog can pick up the virus at a dog park or daycare and not show any bumps until weeks later, making it difficult to trace exactly where the infection started. Like many non-enveloped viruses, papillomaviruses are hardy and can persist on surfaces in the environment, which means shared spaces and equipment can serve as indirect transmission routes even without dog-to-dog contact.
Which Dogs Are Most Susceptible
Young dogs are the most common group to develop warts, particularly oral papillomas. Their immune systems haven’t yet encountered the virus and haven’t built up defenses against it. Puppies and adolescent dogs in social environments like daycares, shelters, and training classes are especially prone because they’re both immunologically naïve and frequently exposed.
When warts appear in older dogs, the cause is typically a weakened immune system rather than first-time exposure. Dogs that are sick, on immunosuppressive medications, or simply elderly may lose the ability to keep a latent papillomavirus in check. Warts in older dogs are worth investigating with a veterinarian, because they can signal underlying immune suppression and carry a higher risk of progressing to more serious growths.
Where Warts Appear and What They Look Like
Warts most commonly show up on the feet, face, ears, and inside the mouth. Foot warts are especially common because walking creates constant minor trauma to the skin, giving the virus easy access. Facial and ear warts tend to develop from self-scratching, which similarly breaks the skin surface. Oral warts, caused primarily by a strain called CPV1, often appear on the lips, gums, and tongue, and are the classic type seen in young dogs.
Most papillomas start as small, smooth bumps and grow into raised, rough-textured masses that can look like tiny cauliflowers. They’re typically flesh-colored to grayish-white. In some cases, a single wart appears in isolation. In others, especially in young dogs with oral papillomatosis, multiple warts can develop and spread across a wide area. The progression to numerous large warts over an extensive area is one of the hallmark features of a full-blown papillomavirus infection.
Warts vs. Other Skin Bumps
Not every bump on a dog’s skin is a wart. Sebaceous hyperplasia, a very common benign growth in dogs, can look similar. These growths tend to be small (under 1 cm), hairless, and pink to yellowish. They’re caused by overgrowth of oil glands rather than a virus. Warts, by contrast, often have a rougher, more irregular surface and may appear in clusters.
More concerning growths, like sebaceous carcinomas, tend to be larger (2.5 to 7.5 cm), may have an ulcerated surface, and can grow aggressively. If a bump on your dog looks unusual, keeps growing, ulcerates, or recurs after removal, a veterinarian can use a simple cell sample or biopsy to determine exactly what it is.
Do Most Warts Need Treatment
Oral papillomas in young dogs generally resolve on their own without any treatment. As the dog’s immune system mounts a response to the virus, the warts shrink and disappear, usually within one to three months. Once a dog’s immune system clears the infection, it typically has lasting immunity to that strain.
Cutaneous warts, the ones that appear on the skin rather than in the mouth, are less predictable. They’re less likely to resolve spontaneously, and some persist indefinitely. When warts are bothersome, located where they cause irritation, or simply won’t go away, veterinarians have several options: freezing them off (cryosurgery), laser removal, surgical excision, or a prescription topical cream that stimulates a local immune response. In severe cases where warts spread extensively and resist treatment, a combination approach may be needed. One documented case of a young dog with widespread, persistent warts required surgical removal of the bulk of the growths, daily topical treatment on remaining lesions, and a course of experimental vaccine injections over ten weeks before the infection was finally controlled.
Can You Catch Warts From Your Dog
Papillomaviruses are species-specific. The strains that infect dogs (CPV1, CPV2, and others) cannot infect humans, and the human papillomaviruses that cause warts in people cannot infect dogs. You don’t need to worry about handling your dog’s warts or sharing your home with an infected pet. The same applies to cats and other household animals: canine papillomavirus does not cross species barriers.
If you have multiple dogs, however, the virus can spread between them. A dog with active warts can be contagious to other dogs, particularly puppies or immunocompromised animals. Keeping infected dogs separated from vulnerable dogs and cleaning shared items and surfaces reduces transmission risk.
Reducing the Risk
Because papillomavirus enters through damaged skin, you can’t fully eliminate risk in a social dog, but you can lower it. Avoid letting your dog share chew toys or water bowls with unfamiliar dogs, especially if you notice warts on another animal. If your dog attends daycare or boarding, ask about their health screening and cleaning protocols.
Effective surface disinfection follows a specific sequence: remove any organic debris first, scrub with a detergent, rinse, let the surface dry, then apply a disinfectant at the correct concentration and leave it wet for the full recommended contact time before a final rinse. Skipping the initial cleaning step or applying disinfectant to a still-wet surface can reduce effectiveness dramatically. Microfiber cloths remove microbes from surfaces more effectively than traditional cotton rags or towels, and should be washed after every use.
For most healthy dogs, the occasional wart is a minor and temporary nuisance. The virus is extremely common in the canine population, and the vast majority of infections resolve without complications once the immune system catches up.