Dog Skin Warts: Pictures, Causes and When to Worry

Dogs get skin warts mainly because of canine papillomavirus, a contagious, species-specific virus that infects skin and mouth cells and pushes them to grow into the small, rough, cauliflower-shaped bumps owners call warts. Any new lump on your dog should be checked by a veterinarian, even one you are fairly sure is a harmless wart, because only a needle sample or a biopsy can tell you what the tissue actually is.

That is the short answer. The longer answer is more useful, because "wart" is a word owners use for at least half a dozen different growths, and the right next step depends on which one you are looking at. This page walks through what causes them, what they look like, why young dogs and senior dogs get different versions, and what a bleeding wart usually means.

The virus behind most canine warts

Papillomaviruses are a family of viruses that infect the outer layer of skin and the lining of the mouth. Dogs have their own types, and those types are highly host specific. You cannot catch warts from your dog, your cat cannot catch them from your dog, and your dog did not get them from you.

Transmission happens dog to dog. Direct nose-to-nose contact, wrestling and mouthing during play, shared water bowls, shared toys, communal bedding and grooming equipment all move the virus around. Places where dogs mix closely, such as boarding kennels, daycare, grooming salons, training classes and busy dog parks, give it more chances to spread.

The virus needs a way in. Intact, healthy skin is a good barrier, so infection usually follows a small break: a scratch, a scrape, a chewed spot, a nick from clippers, or the naturally thin and moist lining of the lips and gums. Warts also do not appear the moment a dog is exposed. There is a lag while the virus multiplies inside the skin cells, which is why owners often cannot link a bump to any specific outing.

What happens next depends almost entirely on the dog's immune system. Research suggests that a cell-mediated immune response is what eventually recognises the infected cells and clears them, which is why papillomas in young, otherwise healthy dogs so often shrink and disappear without any treatment at all. Timelines are not predictable, and results vary from dog to dog. Dogs whose immune systems are busy or suppressed, including those on immune-modulating medication prescribed for another condition, those recovering from illness, and very young dogs whose immunity is still maturing, tend to carry warts longer or develop more of them.

What dog warts actually look like

A classic viral papilloma is small, raised and pale, ranging from whitish pink to grey or light tan. The surface is the giveaway: instead of being smooth like a fatty lump, it breaks into fine fronds or projections, which is where the cauliflower or sea-anemone description comes from. Many sit on a narrow stalk, so they wobble slightly when touched. Some are flatter and plaque-like. Size ranges from barely visible to something closer to a pea, and they can appear singly or in clusters.

Oral papillomas start inside the mouth as smooth pale bumps on the lips, gums, tongue or the inside of the cheeks, then roughen into the frond-like shape over time. Skin papillomas favour the head, eyelids, muzzle, feet and belly, but can turn up anywhere.

Searching for pictures is a reasonable first move, and comparing photos genuinely helps you describe what you are seeing to your clinic. It has a hard limit, though. No photograph can confirm what a growth on your dog is, because several serious skin tumours are deliberate mimics of harmless bumps, and only a veterinarian sampling the tissue can tell them apart.

Growth type	Typical appearance	Common location	Who tends to get it
Oral papilloma	Pale pink or white bumps that roughen into frond-like clusters	Lips, gums, tongue, inside of cheeks	Younger dogs, often after mixing with other dogs
Cutaneous papilloma	Small firm wart on a narrow stalk, rough or cauliflower surface	Head, eyelids, muzzle, legs, abdomen	Middle-aged and older dogs, usually one or a few
Footpad papilloma	Firm, hard, thickened mass on the pad, sometimes cracked	Paw pads and between toes	Any age, may cause limping
Inverted papilloma	Raised firm nodule with a dimple or central pore	Underside of the body and groin	Younger dogs, less common
Sebaceous gland growth	Pink, lobed, slightly greasy bump often mistaken for a wart	Head, eyelids, trunk	Senior dogs
Skin tag	Soft, smooth, floppy flap of skin, not rough	Chest, armpits, pressure points	Older dogs

Young dogs and senior dogs tell different stories

When a young dog suddenly has little warts, especially several of them around the mouth, the usual explanation is a viral papilloma outbreak picked up from other dogs. Puppies and adolescents have immune systems that have not met this virus before, so they mount a slower initial response and can bloom a crop of bumps in a short period. These are the cases that most often regress on their own as immunity catches up.

Senior dogs follow a different pattern. Old dog skin warts are frequently solitary rather than clustered, grow slowly over months, and sit on the skin rather than in the mouth. Some are still viral papillomas. Many are not. Sebaceous gland overgrowths, which are benign enlargements of the skin's oil glands, look remarkably wart-like and are extremely common in older dogs, as are skin tags and small benign cysts. Owners describe all of them as warts, and visually that is a fair description.

The reason this distinction matters is risk, not vanity. Older dogs also have a higher background chance of developing skin tumours that are not benign, and some of those can start out looking modest and unremarkable. So the sensible rule shifts with age: in a young dog with a mouth full of papillomas, a vet may well advise monitoring; in a senior dog with one new bump that was not there last season, examination and sampling carry more weight. If you are tracking changes across your dog's later years, the broader library of canine health conditions is a useful place to see how skin changes fit alongside the other shifts that come with age.

When a wart bleeds, grows or changes

Bleeding is the single most common reason owners move from watching a wart to worrying about it. Most of the time the cause is mechanical. Warts sit above the skin surface on a thin stalk with a blood supply, so they get caught by a collar, snagged on crate bars, nicked by grooming clippers, scraped during play, or licked and chewed until raw. They bleed more than their size suggests, and the bleeding usually stops with a few minutes of gentle pressure using clean gauze.

A single bleed from an obviously traumatised wart is not an emergency. These signs do justify a prompt veterinary appointment:

• Bleeding that returns repeatedly, or will not stop with steady pressure
• Rapid growth, or a bump that changes shape, colour or texture over weeks
• An ulcer, crater or weeping surface rather than a dry, rough one
• Pain when touched, persistent licking, limping, or a bad smell
• Redness, heat or swelling in the surrounding skin
• Drooling, pawing at the mouth, bad breath, or difficulty eating with oral growths
• Several new bumps appearing quickly in an adult or senior dog

Heavy bleeding you cannot control, or any difficulty breathing or swallowing, is a same-day emergency rather than a next-week appointment.

Resist the urge to intervene at home. Do not cut, tie off, freeze, burn or pick at a wart, and do not use human wart removers. Over-the-counter salicylic acid products are formulated for human skin on a human body weight and can cause chemical burns and poisoning in dogs, particularly if licked off. Removal, when it is needed, is a veterinary procedure with pain control and a plan for the tissue afterwards.

Why only an exam can confirm what the bump is

The reason veterinarians sample lumps rather than judging them by eye is that appearance is unreliable. A fine needle aspirate takes a small number of cells with a needle, usually in minutes, without sedation in most dogs, and cytology often gives a clear answer. If it does not, a biopsy examines the architecture of the tissue itself.

Several things sit in the wart-lookalike category: histiocytomas, which are benign button-like growths typical of young dogs; sebaceous adenomas; cysts; skin tags; and mast cell tumours, which are notorious for imitating almost any other skin lesion. Ticks attached close to the skin fool plenty of owners too. None of those are distinguishable from a papilloma by photograph alone, which is exactly why the advice is consistent: talk to your vet about any new bump, and have anything that bleeds, grows or changes looked at rather than watched indefinitely.

Key Takeaways

• Most true dog warts are caused by canine papillomavirus, which spreads dog to dog through contact, shared toys, bowls and grooming tools, and needs a small break in skin or mouth lining to take hold.
• Canine papillomaviruses are species specific, so the virus does not pass between dogs, people and cats.
• Classic papillomas are small, pale and rough-surfaced, often on a stalk, and they favour the mouth, head, eyelids, feet and belly.
• Young dogs tend to get clusters that commonly regress as immunity develops; senior dogs more often get single, slow-growing skin bumps, many of which are not viral at all.
• A wart that bleeds has usually been knocked, scratched or chewed, but repeated bleeding, fast growth, ulceration, pain or colour change warrants a prompt appointment.
• Never cut, tie off or apply human wart treatments to a growth on a dog.
• Photographs narrow possibilities; only a needle sample or biopsy identifies tissue.

Your veterinarian owns the diagnosis here, and that is the right arrangement. They can tell a papilloma from a lookalike, decide whether a growth should be monitored, sampled or removed, and weigh your dog's age, medication history and overall health in that decision. Take a clear photo with something for scale, note when you first saw the bump and whether it has changed, and bring that information to the appointment.

Related reading: What Causes Warts on Dogs and Dog Emergency Signs.