Most of the bumpy growths that appear on aging dogs aren’t actually warts. They’re sebaceous growths, caused by overactive oil glands in the skin, and they’re so common in senior dogs that many elderly pets develop dozens of them over time. True viral warts do occur in dogs, but they’re far more typical in puppies and young dogs. Understanding which type your dog has matters, because the causes, behavior, and outlook are quite different.
What Those “Warts” Usually Are
The lumps that pop up on older dogs are most often sebaceous growths, not viral warts. Sebaceous glands produce the oily substance that keeps your dog’s skin and coat moisturized. As dogs age, these glands can start dividing excessively, producing small, raised bumps that look a lot like warts to the untrained eye. They typically appear as firm lumps under a centimeter across, often with a shiny or slightly waxy surface.
About 50% of these sebaceous growths aren’t technically tumors at all. They’re classified as hyperplasia, meaning an area where gland cells are simply multiplying more than they should. Many veterinary experts believe these pre-tumor growths may eventually progress into benign tumors called sebaceous adenomas, but the key word is benign. They can show up anywhere on the body, and it’s not unusual for a single dog to accumulate scores of them as the years go on.
Why Aging Triggers These Growths
Several changes happen in a dog’s body with age that make skin growths more likely. The skin’s ability to rejuvenate its cellular population slows down, cellular atrophy increases across most structures, and the epidermis itself can thin, especially in very old dogs or those with poor nutrition or hormonal imbalances. These microscopic changes create an environment where abnormal cell growth is harder for the body to keep in check.
The immune system also weakens with age. A younger dog’s immune defenses are better at surveilling the skin for cells that are dividing abnormally and shutting them down. In older dogs, the immune system becomes less efficient at this job, and underlying conditions common in senior pets (hormonal disorders, chronic allergies, immune-mediated skin disease) can compound the problem. The result: geriatric dogs are significantly more likely to develop cutaneous masses, both benign and malignant, than younger dogs. Data from the Dog Aging Project confirms that the lifetime prevalence of both benign and malignant tumors climbs steadily with age.
When They Actually Are Viral Warts
True warts in dogs are caused by the canine papillomavirus and look different from sebaceous growths. Viral papillomas tend to have a rough, cauliflower-like texture rather than a smooth or waxy surface. They most commonly appear around the mouth, lips, and muzzle, though they can show up on the eyelids, feet, or other areas.
Papillomavirus warts are classically a young dog’s problem. Puppies and dogs with immature immune systems are the most susceptible because they haven’t yet built immunity to the virus. That said, older dogs with weakened immune systems can also develop them. If an aging dog’s ability to fight infections has declined due to age or illness, papillomavirus infections can persist longer and produce additional warts that wouldn’t appear in a healthier animal.
Most viral warts in otherwise healthy dogs resolve on their own as the immune system mounts a response. If papillomas stick around for more than three months, treatment and a biopsy are generally recommended to confirm that the growth really is what it appears to be. In rare cases, dogs develop so many oral papillomas that eating and swallowing become difficult, and these can sometimes get infected by bacteria in the mouth, causing pain, swelling, and bad breath.
Telling Harmless Bumps From Concerning Ones
The vast majority of skin lumps on senior dogs are benign. Among benign tumors reported in large studies, roughly 69% are located in the skin, muscle, or soft tissue, making the skin by far the most common site. Still, not every growth is harmless. Malignant skin tumors also become more common with age, and some can initially look similar to a benign wart or sebaceous lump.
Features that warrant closer attention include rapid growth over days or weeks, a surface that ulcerates or bleeds, a growth that feels firmly attached to deeper tissue rather than sitting loosely on the skin, or any lump on the toes (digital papillomas in particular carry a risk of becoming malignant). Pigmented plaques caused by papillomavirus also have the potential to transform into cancer, unlike the more common cauliflower-type warts.
Because many types of growths can appear harmless but behave aggressively, removal and biopsy are often recommended when a lump doesn’t fit the typical pattern for a benign growth, or when the dog’s overall health profile raises concern.
When Removal Makes Sense
Most sebaceous growths on older dogs don’t need to be removed. They’re cosmetic nuisances, not medical threats. However, removal becomes worth considering in specific situations: if a growth is in a spot where it gets repeatedly scratched, bumped, or irritated by a collar or harness; if it bleeds or becomes infected; if it’s growing noticeably; or if your vet can’t confidently identify it by appearance alone.
For viral papillomas, the threshold is similar. Small numbers that aren’t causing discomfort can be left alone. Surgical removal or cryotherapy (freezing) is typically reserved for cases where warts are numerous enough to interfere with function, are located in painful areas, or have persisted long enough to raise questions about what the growth actually is. A biopsy at the time of removal gives a definitive answer.
If your older dog is sprouting new bumps regularly, keeping a simple log of each one (location, size, date you noticed it) makes it much easier to track changes between vet visits and flag anything that’s behaving differently from the rest.