Pitbull mix refusing to have his teeth brushed.

Why Does My Dog’s Breath Smell? Fact Checked By Our Vet

Written By Vedrana Nikolic | Canine Coach, B.A Ethnology & Anthropology, M.A Semiotics.
Edited & Fact Checked By Renae Soppe | B.A Journalism & Science. 
Last Updated: 17th January 2024

Why does my dog’s breath smell so bad? Congratulations. If you’ve found yourself asking this question, you are now officially an experienced pet parent.

But in all seriousness, this is an incredibly common question that tends to come up at least once in every dog’s timeline. This guide is here to help you get to the root of the problem.

What Causes Bad Breath in Dogs?

If you are looking for a simple, straightforward answer, then we are sorry. We can’t give you one! There are many issues that can cause foul-smelling breath in dogs. And, on top of that, a bit of a weird smell is quite normal. If your dog’s breath is suddenly smellier than usual, or if it smells bad, it’s important to investigate the issue.

“Bad dog breath can be a sign of several health issues, and some that you would never guess could be related to your dog’s breath. Understanding why your dog has bad breath is the first step in appropriately treating not only the smell but the underlying cause.” - Riley Shugg, DVM, PetMD (1)

On the bright side, we do know the typical causes for stinky canine breath. And most of the time, the cause will be benign and easy to treat. Below is a list of known causes of halitosis in dogs (the scientific name for bad breath), from the most to the least common.

Related: What Can I Give My Dog for Bad Breath?

#1 Lack of Oral Hygiene

This might or might not come as a surprise, but the number one cause of stinky breath in dogs is poor oral hygiene. Just like humans, dogs need their teeth cleaned for them to remain healthy. The best possible way to do this is by brushing their teeth, but dogs naturally clean their teeth by gnawing on things like bones or chew toys.

Related: Best Dog Toothbrush Australia.

If this is not done enough, however, pieces of food and debris can remain stuck around teeth and cause the breath to smell. Even if you are brushing your dog’s teeth, there might be something stuck somewhere deep in there. It could be anything, from a piece of meat to a tiny piece of a toy or a stick your dog has been chewing. If it has been lodged somewhere in your dog’s mouth for long enough, it will begin to smell. And it can smell bad.

Related: Best Dog Toothpaste.

#2 Dental or Gum Disease

Cavities, tooth decay and periodontal disease are the consequences of neglected dental health. Moreover, sometimes, just like with humans, dogs can suffer from these issues even when you do all you can to keep their teeth clean.

Related: Dog Dental Care Guide Australia.

Most problems of this type are caused by the buildup of plaque (which turns to tartar over time) on your dog's teeth. The main tell-tale signs of plaque buildup are yellow or brown stains on your dog’s teeth. If left untreated, this condition can lead to gingivitis or inflammation of the gums which can cause bigger problems over time.

“If your dog’s teeth are not brushed daily, plaque will accumulate. After 72 hours, that plaque will become mineralized and turn into dental calculus—often referred to as tartar. Tartar is easier for plaque to stick to than the natural smooth surface of the tooth, so it allows for more plaque to accumulate.” - Elizabeth McCalley, DVM, PetMD (2)

This is by far the most common cause of bad breath in dogs. If you are unsure, your dog’s teeth should be the first thing to check. Luckily, it’s an easy problem to solve if treated promptly. But if left neglected, it can just lead to more problems.

#3 Something They Have Eaten

Sometimes the cause of bad breath is very simple: your dog might have eaten something disgusting. Dogs don’t have repulsive feelings towards certain smells and substances as we do, and some of them love to munch on nasty things.

Related: Best Dog Breath Fresheners.

For example, coprophagia is a fairly common problem in dogs - and it refers to eating their poop. Besides that, your dog might be going through your trash, or if wandering around outdoors might have even come in contact with a decaying carcass of another animal.

Yes, all of that sounds pretty awful, but it’s not that strange for dogs. If the foul breath of your dog disappears after a day or two, questionable food choices might be to blame.

#4 Diet & Gastrointestinal Issues

Bad breath in dogs can also be caused by an unbalanced diet. If the gut health of your dog is suffering, the problem might manifest itself as foul-smelling breath. The cause could be a temporary problem with digestion, or it could be something more serious like persistent acid reflux or ulcers. If you suspect this is the cause, it’s best to consult your veterinarian to get to the root of the problem.

#5 Inflammatory Processes

Bad breath in dogs (just like in humans, by the way) can be caused by various inflammations of the upper respiratory tract. This could be sinusitis - inflammation of the sinuses, or rhinitis - the inflammation of the nasal passage. These problems are more common in brachycephalic breeds which more often have breathing problems, but they can happen to any dog.

The causes of upper respiratory infections can be many, some more benign than others. For example, it could be a mild infection, it could be parasites, it could be a foreign body lodge somewhere, or it could be something really serious like a tumour (3).

#6 Diabetes

One of the unexpected causes of strange-smelling breath in dogs is diabetes. Now, smelly breath is not the main sign of diabetes, and there should be other signs you might start noticing earlier, like drinking lots of water, frequent urination, and weight loss.

When diabetes induces changes to a dog’s breath, this is caused by a process called ketoacidosis, and at this point, your dog’s breath can begin smelling strangely sweet. Ketoacidosis is a result of untreated diabetes and it is considered an emergency that requires immediate medical attention (4).

#7 Liver or Kidney Disease

Serious problems with either liver or kidneys can also manifest as bad breath in dogs. Both organs act as the body’s filtration systems, and when they don’t function properly, you can notice it in a dog’s breath. In the case of liver disease, the condition is usually followed by symptoms like yellowing skin, weight loss, and vomiting. In cases of kidney failure, the symptoms could be lethargy and loss of appetite.

My Final Thoughts

Why does my dog have bad breath? Is this normal? Well, most likely, it’s nothing serious. But, stinky breath in dogs is often a sign of poor dental health. It could also be a sign of behavioural problems that need to be corrected, like your dog eating something they shouldn’t be.

In rare cases, it could be something even more serious. In any case, it’s important to find the cause of the smelly problem to resolve it. We hope this guide has helped you!


  1. Shugg, R. February 15, 2022. “9 Reasons Your Dog Has Bad Breath”. PetMD. Retrieved April 19, 2022. https://www.petmd.com/dog/symptoms/9-reasons-your-dog-has-bad-breath
  2. McCalley, E. February 08, 2021. “Periodontal (Gum) Disease in Dogs”. PetMD. Retrieved April 19, 2022. https://www.petmd.com/dog/conditions/mouth/c_multi_periodontal_disease
  3. Burke, A. March 14, 2018. “Bad Breath — More Than Poor Dental Hygiene”. AKC. Retrieved April 19, 2022. https://www.akc.org/expert-advice/health/bad-breath-poor-dental-hygiene/
  4. PetMD Editorial. April 10, 2010. “Diabetes with Ketone Bodies in Dogs”. PetMD. Retrieved April 19, 2022. https://www.petmd.com/dog/conditions/endocrine/c_dg_diabetes_with_ketoacidosis

Vedrana Nikolic

Vedrana Nikolić is Gentle Dog Trainers Canine Coach, Professional Writer, Anthropologist & dog lover.

With a Masters Degree in Semiotics & Bachelors Degree in Anthropology, studying the communication between animals and humans, Vedrana is able to use her expertise to analyse and review dog products and write informative posts on canine behaviour and training.

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