CONDITION
Canine Viral Papillomatosis (Warts)
Canine viral papillomatosis is a condition in which small, rough growths appear on a dog's skin or mucous membranes, most often around the mouth, lips, and muzzle. These growths, commonly called warts, are caused by infection with canine papillomavirus and tend to occur in younger dogs, typically under two years of age, though older dogs with weakened immune systems can also be affected. The growths often appear suddenly and can vary from a single small bump to clusters that may look cauliflower-like in texture. Many owners notice the growths during play, grooming, or feeding, and wonder whether they are painful, contagious, or require treatment. In most cases, the warts cause little discomfort and resolve on their own as the dog's immune system clears the virus, though this can take several weeks to months. Occasionally, growths may bleed if traumatised, or interfere with eating or swallowing if they are large or numerous. This page explores what these growths may look like and where they tend to appear, what is happening beneath the surface as the virus interacts with the immune system, how the condition is investigated and confirmed, and what approaches exist when observation alone is not suitable.
Why this matters now
Canine viral papillomatosis occurs most often in young dogs under two years of age, typically puppies, whose immune systems are still developing. Older dogs with weakened immunity, whether from illness, immunosuppressive medication such as ciclosporin or oclacitinib, or age-related decline, can also develop warts, though this is less common. The virus spreads through direct contact, often in environments where dogs interact closely, such as parks, kennels, or multi-dog households, and can also spread indirectly through shared bowls, toys, or bedding. No breed predisposition has been established for the oral warts described on this page, and the condition can appear in any dog meeting the virus for the first time, most often during a period of immune immaturity or suppression. A separate, non-regressing skin condition caused by a different papillomavirus type, pigmented viral plaques, is seen mainly in Pugs and Miniature Schnauzers, in which a susceptibility to it is thought to be inherited as an autosomal dominant trait, and follows a different course to the warts discussed here.
The growths tend to appear suddenly, often several weeks after exposure, and may begin as small, smooth bumps that gradually develop the characteristic rough, cauliflower-like texture. In most cases, the lesions reach their full size within a few weeks and then begin to regress as the dog's immune system mounts a response, with resolution typically occurring over four to eight weeks, though some cases may persist for up to three months or occasionally longer. The rate of regression can vary between individuals, and a small proportion of dogs, particularly those with ongoing immune compromise, may experience slower resolution or persistent growths. Rarely, a long-standing papilloma can undergo malignant change into squamous cell carcinoma.
Signals & patterns
Early signals
Small, firm bumps on lips or gums
The first sign is often one or several small, pale or pink raised bumps on the lips, gums, tongue, or roof of the mouth. These may feel firm to the touch and are usually noticed during play, grooming, or when the dog yawns.
Clusters appearing rapidly
What begins as a single growth may develop into a cluster of several bumps over the course of days to weeks. Owners often notice that the number of lesions increases noticeably during this early phase.
Rough or textured surface
As the growths enlarge, they tend to develop an irregular, cauliflower-like texture rather than remaining smooth. This change in appearance can make them more obvious when the mouth is examined.
No obvious discomfort
Most dogs show no signs of pain or distress in the early stages. Eating, drinking, and play behaviour typically continue without change, even when multiple warts are present.
Later signals
Bleeding or damaged warts
Larger or more prominent growths may be traumatised during chewing or play, leading to minor bleeding or ulceration. This is usually self-limiting but can cause transient drooling or pawing at the mouth.
Difficulty eating or swallowing
When warts are numerous or located in areas that interfere with movement of the tongue or passage of food, some dogs may eat more slowly, drop food, or show reluctance to chew hard items. This pattern is less common and tends to occur when the lesion burden is high.
Gradual shrinking and darkening
As the immune response develops, individual warts often begin to darken, shrink, and eventually fall off. This process can occur unevenly, with some lesions resolving while others remain, and may be accompanied by mild inflammation at the base of regressing growths.
Click to read about the biological mechanisms
How this is usually investigated
In most cases, the characteristic appearance and location of the growths, combined with the dog's age and history, are sufficient to arrive at a working diagnosis. A veterinary surgeon will take a history that includes the dog's age, immune status, recent contact with other dogs, and the timeline of growth development. When the clinical picture is unclear, for instance, if the growths appear atypical, fail to regress as expected, or occur in an older dog without obvious immune compromise, targeted investigations may be used to rule out other causes or confirm the diagnosis.
Physical examination
Cytology
Histopathology
Polymerase chain reaction (PCR) testing
Options & trade-offs
Management is shaped by the number, size, and location of the growths, the dog's age and immune status, and the degree of interference with normal function. In many cases, no intervention is required, as the immune system clears the virus over time. When growths cause difficulty eating, bleeding, or secondary infection, or when they fail to regress in a reasonable timeframe, a combination of approaches may be considered, tailored to the individual dog and the practical constraints of the household.
Observation and supportive care
Many dogs are managed by monitoring the growths and allowing the immune system time to mount a response, which typically results in spontaneous regression over several weeks to months. During this period, care focuses on minimising trauma to the lesions, such as avoiding hard toys or bones that may cause bleeding, and maintaining good oral hygiene where possible. Soft or moistened food may be offered if the dog shows reluctance to eat due to discomfort.
Trade-offs: This approach requires patience and acceptance that resolution may take time, and it may not be suitable when growths cause significant functional impairment or when the owner finds the appearance distressing. It is most appropriate for young, otherwise healthy dogs with typical lesions and no signs of immune compromise.
Surgical removal
Individual warts or clusters can be excised under general anaesthesia, particularly when they interfere with eating, breathing, or drinking, or when they bleed repeatedly. Removal can also be considered for cosmetic reasons or when the diagnosis is uncertain and tissue is needed for histopathology. Techniques include sharp excision, electrosurgery, or cryotherapy, depending on the size and location of the lesions.
Trade-offs: Surgery carries the usual anaesthetic risks and may result in temporary swelling or discomfort in the oral cavity. Recurrence is uncommon once the dog has mounted its own immune response to the virus, but removal does not prevent new lesions from appearing if viral exposure continues or if immune function remains compromised. The decision to proceed often balances the functional benefit against the practical and financial considerations of anaesthesia.
Immune stimulation
In some cases, veterinary surgeons may consider approaches aimed at accelerating the immune response, such as autogenous vaccines (made from the dog's own wart tissue; these are not authorised medicines, and in the UK they can be made only by a manufacturer holding an autogenous vaccine authorisation, on a vet's prescription under the cascade, where no suitable authorised vaccine exists), topical imiquimod (an immune-modulating cream authorised in the UK for people, with no UK veterinary authorisation, used in dogs under the cascade), or interferon (the feline interferon authorised in the UK for dogs covers parvovirus only, so its use for warts, like that of human interferon, is under the cascade). These methods are intended to shift the balance in favour of viral clearance, though evidence for their efficacy is variable and largely anecdotal. Such approaches are typically reserved for cases with extensive or persistent lesions that are not candidates for straightforward observation or surgery.
Trade-offs: Immune-stimulating therapies are not universally available, and their effectiveness can be unpredictable; some dogs respond well, whilst others show little change. They may involve additional veterinary visits, cost, and monitoring, and are generally considered when conventional management has been insufficient or impractical. Growths at the injection site, including squamous cell carcinoma, have been reported in dogs given a vaccine containing live canine oral papillomavirus, the virus carried in wart tissue.
Addressing underlying immune compromise
In older dogs or those with known immune suppression, whether from disease, medication, or malnutrition, management may include a review of the dog's overall health and any concurrent conditions that might be impairing immune function. This can involve adjusting immunosuppressive drugs where safe to do so, improving nutrition, or treating concurrent infections or parasitism that may be contributing to immune weakness.
Trade-offs: This approach requires careful assessment to identify and address the root cause of immune compromise, and it may not be feasible in every case, particularly when immunosuppressive therapy is needed to manage another condition. The benefit tends to be gradual, and wart regression may still take time even after immune function begins to improve.
Common misconceptions
"Canine warts are contagious to people or other species."
Canine papillomavirus is species-specific and does not infect humans, cats, or other non-canine animals. The virus spreads between dogs through direct contact or contaminated surfaces, but it poses no risk to people handling affected dogs or to other household pets of different species.
"All oral growths in dogs are harmless warts that will go away on their own."
Whilst viral papillomas are common in young dogs and often regress spontaneously, not all oral masses are benign or self-limiting. Older dogs, or those with solitary, rapidly growing, ulcerated, or pigmented lesions, may have other conditions, including squamous cell carcinoma, melanoma, or fibrosarcoma, that require prompt investigation and a different management approach. The age of the dog, the appearance of the growth, and its behaviour over time all inform the level of concern.
"Once a dog has had warts, they will keep coming back throughout life."
In most cases, once the immune system has cleared the virus and the warts have regressed, recurrence is uncommon, as the dog typically develops immunity to that particular strain of papillomavirus. Persistent or recurrent lesions are more likely in dogs with ongoing immune compromise or in those exposed to different viral strains, but the majority of young dogs experience a single episode with no further issues.
Related conditions
Atopic Dermatitis in Dogs
Atopic dermatitis is not itself established as a direct predisposing factor for viral papillomatosis. The recognised link is pharmacological: ciclosporin and oclacitinib are both used in the UK to manage canine atopic dermatitis. The UK product information for oclacitinib lists papilloma as a very common side effect (more than 1 in 10 dogs treated), and that for ciclosporin lists rare wart-like (verruciform) skin lesions (1 to 10 in 10,000 dogs treated), most likely because both dampen the immune activity that would otherwise keep the virus in check.
Demodectic Mange
Demodectic mange and canine viral papillomatosis can both occur when the immune system is immature or compromised, allowing organisms that would otherwise be controlled to proliferate. Young dogs and those with weakened immunity may present with either or both conditions concurrently.
Cutaneous Lymphoma
Cutaneous lymphoma may occasionally enter the differential diagnosis when papilloma-like lesions appear in older dogs or fail to resolve as expected, particularly if the growths are widespread or have an unusual appearance. Histopathology distinguishes benign viral proliferation from malignant lymphocyte accumulation.
Histiocytoma
Histiocytoma is a common, benign skin lump of young dogs, with some 60 to 70 percent occurring in dogs under four years old. It can look similar to a solitary wart when first noticed, particularly before its typical raised, hairless, sometimes reddened appearance becomes obvious. Unlike a viral papilloma, it arises from Langerhans cells rather than a virus infecting the skin surface, but like most papillomas it typically regresses spontaneously, usually within two to four months, as the immune system responds to it.
Oral Melanoma
Oral melanoma is a common and aggressive malignant tumour of the mouth in dogs, occurring mostly in older animals, and a small, pigmented example can resemble a dark wart at first glance. Unlike a viral papilloma it does not regress, tends to enlarge progressively and often ulcerates, which is part of why a new pigmented mass in an older dog's mouth is approached differently to the small, self-limiting warts typical of young dogs.
Squamous Cell Carcinoma
Squamous cell carcinoma can arise in the mouth of older dogs and, when small, may resemble a wart-like growth. It behaves very differently to a viral papilloma, tending to persist, enlarge, and invade local tissue rather than regress, which is part of why a new oral mass in an older dog is not assumed to be a self-limiting papilloma.
If the growths have been present for some time, the features followed over time include whether their appearance, number, or impact on daily life has changed, and whether the dog's overall health and behaviour remain stable. A pattern that differs from typical viral papillomatosis includes a growth persisting beyond around three months without any sign of regression, a single pigmented, ulcerated, or rapidly enlarging mass rather than a cluster of small cauliflower-like bumps, first-time growths appearing in an older dog rather than a puppy or young adult, or new warts developing after starting ciclosporin or oclacitinib. In these situations the differential includes other oral masses such as epulides, squamous cell carcinoma, and melanoma, which behave very differently from a self-limiting viral wart. Oral melanoma and squamous cell carcinoma are more treatable while small, so a growth with any of these features is usually examined, and often sampled for biopsy, soon after it is noticed rather than at the next routine health check. In a dog with a known immune problem or on immunosuppressive medication, warts are usually looked at alongside that condition or medicine.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS