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Bad Breath in Dogs: Investigating Halitosis

A dog’s bad breath may not be a sign of dental disease.

A man with his eyes closed while a dog attempts to lick his face for a kiss.
Photo: Stocksy

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Halitosis is the fancy word for bad breath in dogs, and that odor is nearly always a sign of a bigger problem. Just this week, I noted a slightly foul odor coming from my dog, Dharma. On closer inspection, I noted that the very top of her canine tooth is beginning to turn brown. Overall, the tooth and gum line appear pretty much normal, but I suspect a tooth root infection lurking below.

As in my dog’s case, the cause of bad breath in dogs is most often attributed to dental disease, but there are many other sources of bad breath that should be considered and put on your mental checklist.

Causes for a Dog’s Bad Breath

Is your dog’s bad breath a symptom of something more serious lurking below? Bad breath in dogs could be a sign of illness, let’s look over the checklist:


There are several metabolic causes of bad breath in dogs, these include diabetes and uremia.

  • Diabetes in dogs causes a sweet-smelling breath.

  • Uremia develops with kidney failure when the body cannot clear urea and nitrogen waste products from the blood. With kidney problems, you’ll likely find your dog with bad breath and reminiscence of ammonia.


There are several respiratory causes of bad breath in dogs, these include cancer and foreign objects.

  • Inflammation of the sinuses or nasal passages

  • Cancer/tumors

  • Foreign objects up the nose, such as a piece of stick, food, or even a lodged foxtail.

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Mouth Diseases:

Diseases of the mouth, infection of gums and teeth, and your “basic” dental disease are also common causes of bad breath in dogs.

  • Ulceration of the tissues of the mouth, which can happen with kidney disease or other trauma.

  • Inflammation of the throat or tonsils

  • Cancer/tumors

  • Foreign objects

  • Bacterial, fungal, viral


There are several dietary causes for bad breath in dogs, including what type of food or non-edible items your dog might eat.

  • Eating offensive-smelling food

  • Eating other odorous substances, such as feces


Believe it or not, other causes of bad breath in dogs include electric cords and consuming laundry detergent.

  • Electric-cord injuries, such as biting a live wire

  • Fractures

  • Exposure to caustic agents, such as Tide detergent (Hard to believe a dog would eat that, but I’ve seen it).


There are several other causes of bad breath in dogs, these include infection of the skin and autoimmune diseases.

  • An autoimmune condition where the body can attack itself because it “sees” its own tissues as foreign.

  • Diseases caused by masses in the mouth containing a type of white blood cell known as an eosinophil or eosinophilic granuloma complex.

  • An infection of the skin folds around the lips known as lip-fold pyoderma.

Diagnosing Bad Breath

Bad breath in dogs is a diagnosis that is easily made: Just smelling your dog’s breath at home is the first step. If there is a funky odor, halitosis is present, and there’s a problem. As the list above illustrates, a full spectrum of potential sources of bad breath exist, and interestingly, as varied as these potential causes can be, sometimes the first clinical sign observed in many of them is odor.

If the diagnosis is not obvious from a peek in the mouth (such as a rotten tooth), further steps will be needed to check for other diseases. Once the reason for the bad breath is discovered, your veterinarian can then direct treatment and correct the root cause.

The major takeaway message is that halitosis is not a disease in itself, but that bad breath in dogs is a sign of disease. While bad breath generally indicates an unhealthy mouth, there are many other potential causes to consider, and evaluation of this symptom by your veterinarian is recommended

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Dr. Shea Cox, DVM, CVPP, CHPV

Dr. Shea Cox is the founder of BluePearl Pet Hospice and is a global leader in animal hospice and palliative care. With a focus on technology, innovation and education, her efforts are changing the end-of-life landscape in veterinary medicine.