Is Bad Breath in Dogs a Sign of Illness?

Bad breath in dogs, called halitosis, can have a variety of causes, including illness. A vet explains potential reasons related to disease and sickness.

May 20, 2024·9 min read
Is Bad Breath in Dogs a Sign of Illness?

Dog kisses are great, but stinky dog breath…not so much. Bad breath in dogs, called halitosis, can have a variety of causes. Importantly, bad breath could mean your pup has an underlying health condition that needs to be addressed.  

Learn more about what bad breath in dogs could mean and what you should do if you’re noticing that your dog’s breath stinks. 

Does Bad Breath Mean My Dog is Sick? 

Bad breath in dogs could be a sign of illness, ranging from dental problems to systemic diseases like kidney failure.  

Of course, not all cases of bad dog breath are because of illness! With sudden bad breath in dogs, particularly if it’s short-lived, your dog could have simply eaten something they shouldn’t have.  

Contact your veterinarian if your dog’s bad breath doesn’t go away or if they’re showing other signs of illness such as vomiting, increased thirst, and/or excessive urination. 

Diseases and Illnesses That May Cause Bad Breath in Dogs 

If your dog has halitosis, consider these causes of bad breath in dogs. If you have any concerns about your dog’s breath, you should speak to your veterinarian to receive a proper diagnosis and treatment plan.  

1. Periodontal Disease 

Periodontal disease is infection and inflammation of the tissues surrounding a dog’s teeth. 

Periodontal disease is the leading cause of bad breath in dogs, affecting over 80 percent of dogs over 3 years of age. 

A dog develops plaque both above and below the gum line within several hours of eating. This plaque hardens into tartar over time. The bacteria associated with plaque and tartar cause inflammation of the gums (gingivitis), which eventually leads to pockets between the teeth and gums. These pockets can harbor decaying food and bacteria. Over time, the tissues around the tooth will decay, and the tooth may fall out. 

With periodontal disease, bad breath occurs because of the bacteria causing tissue decay. This decay creates foul-smelling sulfur compounds. Some animals with periodontal disease may occasionally have bleeding in the mouth, which will add a metallic component to the smell. 

Besides halitosis, other signs of periodontal disease include difficulty eating, dropping food, excessive drooling, bleeding on chew toys or in saliva, and a brown or yellow color to teeth. 

2. Oral Tumors 

Tumors in the mouth can cause bad breath if they bleed. The smell you’ll notice is usually metallic. Not all tumors in the mouth are cancerous, but some — like melanoma — are aggressive and dangerous for your dog. 

Other signs of oral tumors to watch for include pain when chewing, dropping food, excessive drooling, a visible lump or mass in the mouth, facial swelling, and bleeding from the mouth.  

3. Lip Fold Pyoderma 

Lip fold pyoderma is an infection of the skin around a dog’s lip folds. Most commonly, this is found in dogs with a lot of loose skin and wrinkles, such as Bulldogs. In this case, the smell you’re noticing may actually be coming from outside your dog’s mouth! You may notice it when you’re up close or if your dog breathes in your face, pushing the odor from their lips towards you. The smell is often described as foul, yeasty, or musty. 

Other signs to watch for include brown discoloration of the fur around the mouth, redness of the skin around the mouth (particularly in a fold), and excessive drooling. 

4. Kidney Disease 

When a dog has kidney disease, their body doesn’t adequately expel toxins in urine. Instead, these toxins build up in the blood. This build-up of toxins in the blood, called uremia, results in foul breath with a chemical, ammonia-like odor. In some cases, dogs with kidney disease can develop sores (ulcers) in their mouths, adding a metallic component to their stinky breath. 

Kidney disease in dogs can occur due to aging, congenital abnormalities, infections, toxins, or cancer. Other signs of kidney disease in dogs can include excessive drinking, excessive urination, decreased appetite, weight loss, and vomiting. 

5. Diabetes 

With unmanaged diabetes, the body breaks down fat and creates ketones. This condition is called diabetic ketoacidosis (DKA), and it is life-threatening for your dog. Dogs experiencing DKA often have a fruity, sweet or acetone smell to their breath. 

Other signs of diabetes include increased urination and thirst, weight loss, and appetite changes. Diabetic dogs experiencing DKA will also act depressed and lethargic, and they frequently vomit. DKA can cause kidney failure, electrolyte abnormalities, and heart failure. 

6. Liver Disease 

Bad breath and liver disease in dogs often go hand-in-hand. The liver is important for filtering out toxins in the blood. When the liver fails, these toxins (such as ammonia) build up. The toxins can create truly foul breath, sometimes compared to rotten eggs, garlic, or a decaying animal. Liver disease can also result in stomach ulcers and bleeding abnormalities, which may contribute a metallic odor to the already unpleasant breath. 

Signs of liver disease to watch for include vomiting, diarrhea, increased thirst, jaundice (yellowing of skin and eyes), abdominal pain, decreased appetite, acting confused, seizures, and issues with blood clotting. 

7. Bleeding in the Mouth 

Bleeding in the mouth causes a metallic odor to the breath. 

Oral bleeding can occur with some of the aforementioned causes, such as periodontal disease or an oral tumor, but bleeding can also occur in pets with coagulation disorders. Some coagulation disorders in dogs are inherited, such as hemophilia or von Willebrand disease. 

Dogs can also develop excessive bleeding if exposed to anticoagulant toxins, such as rodenticides. Bleeding may occur if there is an injury in the mouth, such as a puncture from a stick or a bite from another dog. You can also sometimes smell bleeding in the mouth when puppies are losing their baby teeth

Symptoms to watch for include bleeding from the gumline, small pinpoint bruises on the gums or skin, large bruises on the body, blood in the urine or feces, bloody nose, paleness, swollen abdomen (due to bleeding within the abdomen), and lethargy. 

8. Upper Respiratory Infections 

Upper respiratory infections (URI) can cause changes to a dog’s breath, particularly if the URI is caused by bacteria or if a secondary bacterial infection occurs. The build-up of bacteria, mucus, and discharge from the nasal region can contribute to halitosis. Luckily, the bad breath will go away once the URI resolves, assuming your dog doesn’t have other causes of halitosis as well.  

Other signs of respiratory infections include coughing, sneezing, discharge from the eyes or nose, lethargy, and reduced appetite. Some URIs can lead to pneumonia, so make sure to contact a veterinarian for an evaluation if you suspect your pet has an upper respiratory infection. 

Dental Problems Vs. Other Illnesses 

Bad breath in dogs is usually caused by dental problems, most commonly periodontal disease.  

To determine if the cause of bad breath is due to dental problems, pet parents can look for: 

  • Exposure of tooth roots or loss of teeth 
  • Redness along the gums 
  • Bleeding around the gums 
  • Fractured teeth 

If your dog is having difficulty chewing or is dropping their food, this is another indication that your pet may have dental issues leading to bad breath. 

If you’re noticing other signs like vomiting, excessive urination or thirst, or jaundice, you should assume there is a systemic cause of bad breath that needs quick veterinary attention. Keep in mind that it’s possible (and common) for dogs with systemic health issues like kidney disease to also have periodontal disease. 

Visiting a veterinarian is the best way to determine what is causing your pet’s bad breath. If your dog is otherwise acting normal and has bad breath, you’re usually safe to simply set an appointment with your veterinarian. However, if your pet is vomiting, seems weak, is jaundiced, or is otherwise ill, consider seeking emergency attention for your pet. 

Other Causes of Dog Bad Breath 

Again, not all causes of bad breath in dogs are due to disease. Here are some other causes of stinky dog breath that are not related to illness: 

Eating things they shouldn’t. Just like you may not have the most pleasant breath after eating certain things, your dog’s breath can change with what they consume. If your dog eats poop (coprophagia), gets into the trash can, or finds a deceased animal outside, they may have short-lived stinky breath. 

Something stuck in their teeth. Your dog could also have changes to their breath if they have foreign objects stuck between their teeth. If you suspect this is the cause, your veterinarian can do a thorough mouth examination and remove the foreign object. 

Excessive licking. Excessive licking may cause bad breath if your dog is repeatedly licking a wound, their anal area, or similar areas on other dogs. 

In Conclusion: Bad Breath and Illness in Dogs 

If you’re concerned about your dog’s breath, consult with your veterinarian.  

Because dental problems are the most common cause of bad breath in dogs, preventative dental care is your best tool for warding off halitosis. Preventative dental care for dogs includes daily brushing of teeth and using at-home dog dental care products.  

Speak with your veterinarian about full dental cleanings for optimal canine oral health.

Rhiannon Koehler, DVMR

Rhiannon Koehler, DVM

Dr. Rhiannon Koehler is a veterinary writer who aims to provide accurate, veterinarian-written content that pet parents can use to make better health decisions for their pets. As the founder of Evergreen Medical Writing, LLC, her writing is exclusively in the veterinary and biomedical spaces. In addition to writing new content, Dr. Koehler also provides her veterinary expertise as a medical reviewer, ensuring content is medically accurate and reflects the most current veterinary practices. Clinically, Dr. Koehler mostly works with animal shelters, low-cost clinics, and wellness clinics. She believes strongly in the mission of such organizations to provide affordable care to underprivileged pets and families. She graduated from the University of Missouri with her Doctor in Veterinary Medicine and her Masters in Public Health and has over a decade of experience in the veterinary industry.

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The information contained within this site is not intended as a substitute for professional medical or veterinary advice. PetLab Co. is not intended to diagnose, treat, cure or prevent any disease. If your pet has, or you suspect your pet has any medical condition, you are urged to consult your veterinarian. Medical conditions can only be diagnosed by a licensed veterinarian. These statements have not been evaluated by the Food and Drug Administration. Results May Vary. Not intended for human consumption. Please consult your veterinarian regarding any change in treatment or supplementation.
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