What Causes Bad Breath in Dogs? And What Can I Do About It?

Bad breath isn’t always a sign of illness, says Ashly Smith, DVM, regional medical director for Small Door Veterinary.   

“Mild or temporary bad breath can result from dietary choices or licking smelly things,” Dr. Smith says. “However, persistent bad breath is often a sign of an underlying issue, such as dental disease or a systemic health condition, so it shouldn’t be ignored.” 

When your dog’s breath can’t be dismissed as the aftermath of a questionable backyard snack, it might point to a more serious issue.  

The most common causes of bad breath in dogs include:  

Periodontal Disease  

“The most common cause of bad breath in dogs is periodontal disease, which is caused by plaque and tartar building up on their teeth,” explains Ray Spragley, DVM, founder of Zen Dog Veterinary Care, in Tuckahoe, New York. This buildup is full of bacteria, which release stinky sulfur compounds that create an unpleasant odor. 

Untreated periodontal disease can also lead to infection and tooth decay, as well as abscessed teeth, all of which can further contribute to the unpleasant smell. 

Something Stuck in Their Teeth or Mouth  

Dogs who like to chew on bones, toys, ropes, or sticks risk having foreign objects become lodged between their teeth or in their mouths. Left untreated, this—along with cuts and scrapes in their mouth—can result in an infection that causes bad breath.  

Ingestion of Something Stinky or Toxic  

“Dogs who scavenge or eat inappropriate items (like garbage or feces) may develop temporary bad breath,” Dr. Smith says.  

Bad breath can also be a sign that your dog has ingested something toxic, such as certain plants, chemicals, or human foods like onions or garlic.  

If you suspect poisoning, immediately contact your vet or the Pet Poison Helpline at (855) 764-7661. A consultation fee applies. 

Gastrointestinal Issues 

When digestion isn’t working as it should—whether due to food allergies, poor diet, or chronic inflammation—it can lead to an overgrowth of harmful bacteria in the gut.  

Referred to as “dysbiosis,” this can cause issues such as acid reflux, poor nutrient absorption, and gases from undigested food traveling up the esophagus, all of which can contribute to bad breath. 

Kidney Disease 

Bad breath that has an ammonia (urine-like) smell to it is often a red flag for kidney disease in dogs.  

When the kidneys aren’t functioning properly, toxins called urea that are normally filtered out of the blood build up, leading to distinct-smelling bad breath, explains Dr. Spragley.  

This condition is usually accompanied by other symptoms, such as vomiting, increased thirst, frequent urination, and lethargy.  

Liver Disease 

A malfunctioning liver struggles to filter toxins from the bloodstream, which can result in stinky breath.  

Other warning signs of liver disease can include vomiting, diarrhea, or a yellowish tint to the gums and eyes. 

Diabetes 

“Diabetes can cause your dog’s breath to have a sweet smell to it,” Dr. Spragley says. “This happens due to the very high glucose levels in their bloodstream.”  

Other symptoms of diabetes include increased thirst, weight loss, and frequent urination.  

Oral Tumors 

Oral tumors, whether benign or malignant, can cause bad breath due to tissue decay and infection in the affected area, says Dr. Smith. These growths might also make it difficult for your dog to eat or chew normally.  

If your dog has persistent bad breath or shows any other unusual symptoms, take them to the vet ASAP.   

The vet will perform a thorough examination, which might include:  

• Checking the teeth and gums 
• Assessing the mouth for injuries or infections  
• Conducting blood work or imaging to rule out systemic issues, such as kidney or liver disease  

Treatment depends on the diagnosis: 

• For dental disease, a professional cleaning or tooth extraction might be required.  
• Infections or injuries might be treated with antibiotics or other medications, like pain meds.  
• Systemic conditions such as diabetes or kidney disease will need specific treatments to manage the underlying problem.  

You can try several oral hygiene strategies to tackle your dog’s bad breath.  

If the odor is due to early plaque buildup, these methods might eliminate it entirely. However, Dr. Smith stresses that they won’t resolve bad breath caused by more serious conditions, such as periodontal disease or systemic illness. 

That said, the following practices can help reduce the smell while you address the underlying issue with your vet: 

• Brush your dog’s teeth daily. Use a dog-safe toothbrush and dog-safe toothpaste. This helps remove odor-causing plaque and reduces the risk of dental disease, Dr. Smith explains.  
• Offer dental chews. Dental treats for bad breath in dogs can stimulate saliva production and scrape away plaque and tartar as your dog chews, Dr. Smith says. Some dental chews, such as OraVet Dental Hygiene Chews, also have coatings that prevent bacterial attachment.   
• Try water additives or food powders. Water additives, which are added to your dog’s water bowl, often contain enzymes or antimicrobial agents to reduce bacteria and freshen breath, Dr. Smith notes. Dental powders, like ProDen PlaqueOff Powder, are another option; you can add them to your dog’s wet or dry food.  
• Use dental wipes or rinses. Keep dental wipes or rinses on hand for quick and easy oral care. They’re particularly good for those times when brushing isn’t an option or in between brushing sessions.   
• Provide dental toys. Dental dog toys, like the KONG Dental Dog Toy, can help scrape away plaque as your dog chews. Bonus? They will keep your pup entertained—win-win!  
• Consider a dental diet. Dental dog foods—Hill's Science Diet Adult Oral Care—are specifically formulated to reduce plaque, tartar, and bad breath. These diets often feature specially shaped kibble that helps clean your dog’s teeth as they chew. Speak with your vet before switching your dog’s food, though. 

When choosing dental products, Dr. Smith recommends choosing those accepted by the Veterinary Oral Health Council (VOHC). “This ensures the product has been independently tested and proven to be effective at reducing plaque and tartar,” she says.  

• Prioritize dental health. Good oral hygiene is the most impactful way to prevent bad breath. Regular brushing and incorporating VOHC-approved products, such as dental chews or water additives, can go a long way toward keeping your dog’s mouth healthy and odor-free. 
• Schedule routine vet checkups. Regular checkups help catch dental disease and conditions such as diabetes early, ensuring your pup receives prompt treatment for conditions that can harm their health and cause bad breath.  
• Get an annual professional dental cleaning. “A veterinarian can remove tartar, take dental X-rays, and extract infected teeth,” Dr. Smith says. “This is the gold standard for addressing advanced dental disease, which is a major cause of bad breath.” 
• Provide a healthy diet. A nutritious, dog-appropriate diet supports overall health and oral hygiene. Treats, including human food, should make up no more than 10% of your dog’s diet.  
• Monitor your dog’s behavior. Keep a close eye on your dog to prevent them from eating anything gross or potentially toxic that might cause bad breath or harm.