Investigating Halitosis

Bad breath may not be a sign of dental disease
By Shea Cox DVM, March 2012, Updated July 2016

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

As in Dharma’s case, the cause of halitosis is most often attributed to dental disease, but there are many other sources of odor that should be considered and put on your mental checklist. These can include:

Metabolic causes:

  • Diabetes.
  • Uremia: This develops with kidney failure, when the body cannot clear urea and nitrogen waste products from the blood.

Respiratory causes:


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  • 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.

Dermatologic causes:

  • Infection of the skin folds around the lips, known as lip-fold pyoderma.

Dietary causes:

  • Eating offensive smelling food.
  • Eating other odorous substances, such as feces.

Diseases of the mouth, in addition infection of gums and teeth, your “basic” dental disease:

  • 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.

Trauma causes:

  • 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).

Infectious causes:

  • Bacterial, fungal, viral.

Miscellaneous causes:

  • Autoimmune causes: A 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.

Halitosis is a diagnosis that is easily made: Just smelling your dog’s breath at home is the first step. If there is a disagreeable odor, halitosis is present, and there’s a problem. As the list above illustrates, a full spectrum of potential sources of “yuck mouth” 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 bad tooth), further steps will be needed check for other disease. Once the reason of the bad breath is discovered, therapy can then be directed at correcting the cause.

The major take-away message is that halitosis is not a disease in of itself, but 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.

Veterinarian Shea Cox has enjoyed an indirect path through her professional life, initially obtaining degrees in fine arts and nursing. She later obtained her veterinary medical degree from Michigan State University in 2001 and has been practicing emergency and critical care medicine solely since that time. In 2006, she joined the ER staff at PETS Referral Center in Berkeley and cannot imagine a more rewarding and fulfilling place to spend her working hours. In her spare time, she loves to paint, wield her green thumb, cook up a storm and sail. Her days are shared with the three loves of her life: her husband Scott and their two Doberman children that curiously occupy opposite ends of the personality spectrum.