Short answer
Most bad breath in dogs comes from dental disease: bacteria in plaque and tartar make smelly sulfur compounds. A cleaning, often under anesthesia at the vet, treats the cause; fresheners do not. The AVMA lists sweet-smelling breath as a sign of diabetic ketoacidosis: call a vet immediately. Lasting bad breath, mouth sores or trouble eating need an exam.1, 3, 7, 8
This page covers what veterinary references say about the causes of dog bad breath, which signs mean a vet visit, and what daily care can do. It tests nothing on dogs. Data checked on October 13, 2026. For removing build-up on the teeth, see how to remove plaque and tartar from dog teeth.
What causes bad breath in dogs?
VCA calls periodontal disease from plaque and tartar build-up the most common cause, and says the primary cause of the smell is bacteria causing decay that creates sulfur compounds.1 Merck’s owner page names hydrogen sulfide and ammonia among the bacterial waste products that build up and damage tissue in gum disease, and says bad breath is common with gingivitis.4 VCA’s list of causes also includes decomposing food trapped in gum pockets, persistent bleeding from clotting problems, and tissue death from oral tumors.1
| Cause | What the source says | Next step |
|---|---|---|
| Periodontal disease (plaque, tartar, gingivitis) | The most common cause; small and flat-faced breeds are more prone because teeth are crowded.1 | Veterinary exam and cleaning under anesthesia, with X-rays; daily plaque control afterwards.1 |
| Abscessed tooth | Bacteria reach the tooth root; may cause swelling of the jaw or under the eye. VCA calls broken and abscessed teeth common in dogs that chew hard items such as bones.2 | Veterinary exam. |
| Foreign body | Objects such as sticks can lodge between teeth and cause infection and ulcers.2 | Veterinary exam. |
| Oral mass or tumor | Can go unnoticed until large; bad breath may be the first sign.2 | Veterinary exam. |
| Other mouth inflammation | Merck says bad breath is severe in trenchmouth (necrotizing ulcerative gingivitis) and common with mouth and tongue inflammation.5 | Veterinary exam. |
| Disease outside the mouth | VCA names kidney disease and diabetes as the classic examples of disease outside the mouth that can affect breath.2 | Veterinary exam with tests; see the next section. |
Is bad breath in dogs a sign of illness? When should I call the vet?
Bad breath is itself on Cornell’s list of reasons to contact your vet, along with trouble eating or lower appetite, bleeding from the mouth, swelling of the jaw or face, drooling, and nasal discharge.3 VCA’s advice is not to assume a smell comes from something the dog ate: talk to your veterinarian to make sure the mouth is healthy.2
Two sourced signs deserve faster action:
- Sweet-smelling breath. The AVMA’s diabetes brochure lists sweet-smelling breath among the signs of diabetic ketoacidosis, a potentially life-threatening condition, together with being quieter than usual, reluctance to eat or drink, vomiting, diarrhea, rapid or troubled breathing, and weakness or collapse. It says to contact your veterinarian or an emergency clinic immediately.7
- Mouth sores with other signs. Merck lists mouth sores among the signs of advanced (stage IV) chronic kidney disease, along with vomiting, depression, loss of appetite, weight loss, dehydration and diarrhea.8 Mouth sores are not specific to kidney disease, so a vet has to sort out the cause.
The references cited here do not describe other breath smells (urine-like, fishy or fecal) as tests for a specific disease, and neither should an owner. Any new or sudden change in your dog’s breath, or breath that stays bad after teeth care, is a reason to ask your veterinarian for an exam. VCA also recommends dental exams at least twice a year.1
What causes rotten breath, and how do I get rid of the smell of rotting teeth?
A rotten smell usually means infection and tissue breakdown around the teeth: periodontal pockets, a diseased root, or an abscess.1, 2, 4 Merck says periodontitis, once it starts (usually at 4 to 6 years), is irreversible and often needs cleaning above and below the gum line, sometimes surgery, and often extractions.4 VCA describes treatment as a full oral exam, tooth-by-tooth X-rays, cleaning and polishing under general anesthesia, and extraction of teeth with advanced disease.1
So the only fix we found for a rotting-tooth smell is treating the cause. A chew, spray or water additive can reduce plaque on a healthy mouth, but none of the references cited here says one clears an infected pocket or an abscessed tooth. Once the mouth is treated, VCA says daily plaque control is essential.1 The guide to cleaning teeth without brushing covers the options.
What can I feed my dog to get rid of bad breath? What kills dog breath naturally?
The sources are cautious. Merck’s owner page says dogs eating a regular diet of hard kibble have fewer problems because chewing cleans the teeth, and that your veterinarian may recommend special foods, toys and treats that help remove plaque.4 Merck’s veterinary reference adds that the idea of kibble as a mechanical cleaner does not always hold true, and that some dental diets contain ingredients such as polyphosphates to slow mineralization.6 VCA says zinc-containing oral care products may reduce odor, because zinc binds sulfur compounds.1
Parsley, yogurt, vinegar and homemade breath fresheners are popular answers online. The veterinary references cited here do not mention them, and we found no veterinary source that supports any of them as a treatment for the cause of the smell; the claims we saw came from pet blogs without cited studies. That is not evidence that they are harmful, only that they are unproven. A food that masks odor does not remove the plaque and bacteria VCA names as the cause. Ask your veterinarian before changing a diet or adding something to the water bowl.
Which products have a VOHC claim, and do they cover breath?
VCA says VOHC-accepted products, including dental diets, treats, water additives and topical products, have shown plaque and tartar reduction in studies.1 That is what the Seal covers: VOHC awards it for plaque, calculus (tartar), or both, and the VOHC page cited here does not mention bad breath.9 So a VOHC Seal tells you about plaque or tartar in the trials, not about breath. Trials of two individual chews that measured breath compounds are summarized in do dental chews work.
On the list we checked, VOHC had 37 edible-chew rows, 14 dental-diet rows and 26 rows for water additives, gels, sprays, toothpastes and powders, plus 4 for brushes and wipes.10 Use the VOHC-accepted dental chews page for chews and VOHC dental powders, water additives and wipes for the rest. Check the exact product line: a brand is not accepted as a whole.
What daily routine keeps dog breath fresh?
Merck recommends brushing daily, and wiping the teeth with gauze at least every 2 to 3 days for dogs that will not allow a brush.4 Human toothpaste should not be used.4 Add the veterinary dental exams VCA recommends, at least twice a year,1 and more often if your vet advises, since Cornell says exam frequency depends on a dog’s age, breed and dental health.3
Frequently asked questions
What can I feed my dog to get rid of bad breath?
No food cures the cause. Merck says dogs on regular hard kibble have fewer dental problems, and your vet may recommend dental diets or VOHC-accepted treats. Bad breath that persists needs an exam.
What kills dogs' bad breath naturally?
We found no veterinary source showing a natural remedy kills the bacteria behind bad breath. VCA says plaque control and professional cleaning treat the cause. Ask your vet before trying home mixes.
What causes rotten breath in dogs?
Usually bacteria under the gum line from periodontal disease, an abscessed tooth, a foreign body or an oral mass. A vet exam finds which.
How to get rid of the smell of rotting teeth in a dog's mouth?
VCA describes treatment as an oral exam, X-rays, cleaning and polishing under anesthesia, and removal of badly diseased teeth. Home products do not replace this.
Is bad breath in dogs a sign of illness?
VCA names kidney disease and diabetes as classic examples of illness that can affect breath, and the AVMA lists sweet-smelling breath among diabetic ketoacidosis signs that need immediate veterinary contact. Most cases are dental, but a vet should check.
Do dental chews help with bad breath?
Some chew trials measured breath compounds; see do dental chews work. VOHC awards its Seal for plaque and tartar, not breath.
Sources
- VCA Animal Hospitals: What causes halitosis in dogs?, accessed October 13, 2026. Causes, sulfur compounds, treatment under anesthesia, VOHC products, zinc, twice-yearly exams.
- VCA Animal Hospitals: Five reasons your pet may have bad breath, accessed October 13, 2026. Periodontal disease, abscess, foreign body, oral mass, systemic disease.
- Cornell University College of Veterinary Medicine: Dental disease and home dental care, accessed October 13, 2026. Signs to contact your vet, exam frequency.
- Merck Veterinary Manual: Dental disorders of dogs (owner version), accessed October 13, 2026. Bacterial compounds, gingivitis and periodontitis, brushing, gauze, diet, treatment.
- Merck Veterinary Manual: Disorders of the mouth in dogs (owner version), accessed October 13, 2026. Bad breath with mouth inflammation, trenchmouth and tumors.
- Merck Veterinary Manual: Periodontal disease in small animals (veterinary version; page updated April 2025), accessed October 13, 2026. Halitosis as a clinical sign, kibble and dental diets.
- American Veterinary Medical Association: Diabetes in pets (client brochure, 2024), accessed October 13, 2026. Sweet-smelling breath among diabetic ketoacidosis signs.
- Merck Veterinary Manual: Noninfectious diseases of the urinary system in dogs (owner version), accessed October 13, 2026. Mouth sores among signs of advanced chronic kidney disease.
- Veterinary Oral Health Council: VOHC home page, accessed October 13, 2026. Seal covers plaque, calculus or both; VOHC does not test products itself.
- Veterinary Oral Health Council: Accepted products, accessed October 13, 2026. Row counts by category in the VOHC snapshot of October 13, 2026.