Gum overgrowth, which vets call gingival hyperplasia, is gum tissue that keeps thickening until it creeps over the teeth. In dogs it has two main causes. Some dogs inherit a tendency to grow extra gum when plaque inflames it, Boxers above all. In others it's a side effect of a long-term medicine, most often amlodipine for the heart or blood pressure, or cyclosporine for skin and immune disease.
It isn't something you can shrink at home, and it doesn't settle while the cause is still there. Any new growth on a dog's gum deserves a vet check, usually with a biopsy, because overgrowth and mouth tumors can look the same. The extra gum also traps plaque, so left alone it feeds the periodontal disease that loosens teeth.
What gum overgrowth looks like
Most dogs react to inflamed gums the opposite way. The gum shrinks back and the roots start to show. In a dog with gingival hyperplasia the gum grows instead. You see firm, pink, thick gum that rises up the teeth, often all the way around the mouth, until only the tips of some crowns poke out. Sometimes it's one smooth lump next to a single tooth.
Normal gum hugs the tooth with a shallow groove. Overgrown gum stands up over the crown and leaves a deep collar that vets call a pseudopocket, because the gum has grown up rather than the bone being lost. Plaque, the soft film of bacteria on teeth, packs into that collar where no brush or chew reaches. It hardens into tartar, inflames the gum further and keeps the cycle going.
That's why a dog with overgrown gums often has bad breath and gums that bleed when it chews. Food gets trapped in the pockets too. It starts as gingivitis, the reversible stage of gum disease, but plaque sitting in deep pockets for months can move on to periodontitis, where the ligament and bone around the root are destroyed. Bone doesn't grow back.
Why Boxers grow extra gum
Boxers have been known for this since a 1952 report described gum overgrowth running in Boxer families (Burstone and colleagues). Bulldogs are prone too, and Cocker Spaniels less often. The genes behind it haven't been found yet.
The UK's VetCompass records covered 3,219 Boxers under the care of vets in 2016. An epulis, a firm growth on the gum, was recorded at least once that year in 188 of them, or 5.84%, which made it the second most common specific problem in the breed. That's about 1 in 17 Boxers within that one year. The median age of the dogs with an epulis was just under 9 (O'Neill and colleagues, Canine Medicine and Genetics, 2023).
The kind of epulis Boxers are known for has long been filed as a benign tumor, the peripheral odontogenic fibroma. In a 2026 study of 100 of them, the authors argued it is more likely the gum's own ligament overgrowing in reaction to irritation, and proposed a new name (Bell and colleagues, Veterinary Pathology). That is their reading of the tissue, and they say the cause can't be settled with certainty. Either way, a Boxer's gums need looking at regularly from middle age, and new growth goes to the vet.
In these dogs the gum tends to grow back after it's trimmed, even after a good operation, which is why vets plan re-checks.
Medicines that can make the gums grow
Gum overgrowth is a known side effect of some long-term medicines in dogs, and it usually starts a few months after the dog begins the drug.
- Calcium channel blockers such as amlodipine, for high blood pressure and some heart disease
- Cyclosporine, for itchy skin allergies and immune disorders
- Rarely, the older seizure drug phenytoin
Amlodipine has the clearest numbers. In 82 dogs with heart valve disease given it and followed for more than six months, 7 (8.5%) developed overgrown gums, and none sooner than 5 months into treatment. After their vets stopped the drug, the gums began to shrink within 2 weeks and were back to normal within 6 months. One dog restarted amlodipine and the overgrowth returned within 4 months (Thomason and colleagues, Journal of Veterinary Internal Medicine, 2009).
With cyclosporine, overgrowth is an uncommon side effect in dogs. In an experiment with the high doses used after kidney transplants, 3 of 4 dogs developed it, and the first change showed at about 20 weeks in the small triangles of gum between the teeth (Nam and colleagues, Veterinary Surgery, 2008). Those triangles are the place to look if your dog takes cyclosporine long term.
When the drug can't simply be changed, vets sometimes add the antibiotic azithromycin. In a series of six dogs on cyclosporine it cleared the overgrowth completely (Diesel and Moriello, 2015). A placebo-controlled trial in 36 dogs was less convincing. It reduced pocket depth but fully cleared the overgrowth in only one dog (Rosenberg and colleagues, Veterinary Dermatology, 2013).
Never stop or cut a prescribed medicine yourself because of your dog's gums. Amlodipine may be holding blood pressure or a heart condition in check, and cyclosporine an immune disease. Tell your vet what you've noticed and when the drug was started, and let them weigh the gums against what the drug is treating. In a Great Dane whose overgrowth followed 16 months of amlodipine, the vet switched to a different blood pressure drug and the gums had nearly recovered 9 months later (Pariser and Berdoulay, 2011).
Why every gum growth needs a biopsy
By eye, harmless overgrowth, benign tumors and cancer can look alike. In 403 dogs whose mouth growths were biopsied at a specialist dental practice, 37% were malignant, 34% were tumors arising from tooth-forming tissue and 28% were inflammatory (Wingo, Journal of Veterinary Dentistry, 2018). A needle sample often can't tell them apart, so vets take a proper piece of tissue for the microscope.
See your vet within a week or two if you notice any of these, and sooner if it's growing fast.
- Gum that has started to cover part of the teeth
- A lump on one side only, or next to a single tooth
- A growth with an open sore on it, or bleeding gums around a lump
- A growth that is getting bigger week by week
- A tooth that has become loose or moved out of line
- Swelling of the face or jaw
- Dropping food, chewing on one side, or pawing at the mouth
- Any change in the gums of a dog on amlodipine, cyclosporine or a seizure medicine
What the vet does
Your vet will look in the mouth while your dog is awake, but the real assessment happens under general anesthesia. That means probing around every tooth, full-mouth dental x-rays to see the bone and roots under the extra gum, a cleaning, and a biopsy of anything that looks like a mass.
The treatment for overgrowth is surgery. The vet trims the excess gum back to a normal height (gingivectomy) and reshapes the edge (gingivoplasty), usually with local nerve blocks for comfort. Teeth that are already badly loose may be taken out at the same time. Expect pain relief for several days, and soft food for about two weeks while the gums heal, with hard chews and toys put away.
In inherited cases the gum often grows back, so many dogs need the procedure repeated over the years. Vets usually suggest a check every 6 to 12 months to catch it early, when the trim is smaller.
What home care can and can't do
Nothing you put on the gums or in the food, whether a powder, rinse, gel or "natural" remedy, will shrink overgrown gum tissue. If the gum is already over the teeth, the plaque in those pockets is beyond a brush, and that is a job for the vet.
Home care matters after the surgery. Inflammation from plaque is one of the triggers for the gum to grow, so keeping plaque off the new, normal gum line may slow the regrowth. Daily brushing with a dog toothpaste is the best tool, started once your vet says the gums have healed. In a Boxer, Bulldog or a dog on one of the drugs above, lift the lip once a month in good light and look at the gum edge and the little triangles between the teeth. A photo each time makes slow change easy to spot.
Questions owners ask
Is gum overgrowth in dogs cancer?
Overgrowth itself isn't cancer. It's extra normal gum tissue. But a mouth tumor can look just like it, and only a biopsy tells them apart, so any new growth needs a vet check.
Can gum overgrowth go away on its own?
Inherited overgrowth doesn't. It needs trimming and tends to come back. Overgrowth caused by a drug often shrinks over weeks to months if the vet changes or stops that drug. Never stop a medicine yourself.
Does gum overgrowth hurt my dog?
The extra gum isn't usually painful in itself. The infection that builds up in the deep pockets can be, along with gums that bleed when your dog chews. Many dogs hide mouth pain well, so a dog that's still eating can still be sore.
References
- Bell CM, Murphy BG, Soukup JW. Histomorphologic evidence supports a hyperplastic pathogenesis of fibromatous epulis of periodontal ligament origin/peripheral odontogenic fibroma and proposal of fibromatous hyperplasia of the gingival ligament as unifying nomenclature. Vet Pathol. 2026;63(6), 1001-1012. doi 10.1177/03009858261457960
- Burstone MS, Bond E, Litt R. Familial gingival hypertrophy in the dog (boxer breed). AMA Arch Pathol. 1952;54(2), 208-212.
- Diesel A, Moriello K. Medical management of cyclosporine-induced gingival overgrowth using oral azithromycin in six dogs. Vet Sci. 2015;2(1), 13-22. doi 10.3390/vetsci2010013
- Dosenberry C, Arzi B, Palm C, Vapniarsky N, Soltero-Rivera M. An update on oral manifestations of systemic disorders in dogs and cats. Front Vet Sci. 2024;11, 1511971. doi 10.3389/fvets.2024.1511971
- Lewis JR, Reiter AM. Management of generalized gingival enlargement in a dog, case report and literature review. J Vet Dent. 2005;22(3), 160-169. doi 10.1177/089875640502200303
- Nam HS, McAnulty JF, Kwak HH, et al. Gingival overgrowth in dogs associated with clinically relevant cyclosporine blood levels, observations in a canine renal transplantation model. Vet Surg. 2008;37(3), 247-253. doi 10.1111/j.1532-950x.2008.00373.x
- O'Neill DG, Skipper AM, Barrett K, Church DB, Packer RMA, Brodbelt DC. Demography, common disorders and mortality of Boxer dogs under primary veterinary care in the UK. Canine Med Genet. 2023;10, 6. doi 10.1186/s40575-023-00129-w
- Pariser MS, Berdoulay P. Amlodipine-induced gingival hyperplasia in a Great Dane. J Am Anim Hosp Assoc. 2011;47(5), 375-376. doi 10.5326/jaaha-ms-5565
- Rosenberg A, Rosenkrantz W, Griffin C, Angus J, Keys D. Evaluation of azithromycin in systemic and toothpaste forms for the treatment of ciclosporin-associated gingival overgrowth in dogs. Vet Dermatol. 2013;24(3), 337-345. doi 10.1111/vde.12033
- Thomason JD, Fallaw TL, Carmichael KP, Radlinsky MA, Calvert CA. Gingival hyperplasia associated with the administration of amlodipine to dogs with degenerative valvular disease (2004-2008). J Vet Intern Med. 2009;23(1), 39-42. doi 10.1111/j.1939-1676.2008.0212.x
- Wingo K. Histopathologic diagnoses from biopsies of the oral cavity in 403 dogs and 73 cats. J Vet Dent. 2018;35(1), 7-17. doi 10.1177/0898756418759760