Dog Bad Breath: Causes, Smells and Remedies

A bit of doggy smell is normal. A mouth that makes you turn your head away isn't. The medical word for it is halitosis, and in dogs it usually means bacteria are busy in the mouth.

The good news is that most cases have a simple cause and a simple fix. The less good news is that a few smells point to illness elsewhere in the body. This guide shows you how to tell them apart.

What bad breath in a dog really is

Your dog's mouth is warm, wet and full of food. That's a great place for bacteria to live. When they break down food scraps and dead cells, they release sulfur compounds. Those compounds smell like rotten eggs.

You might notice this as breath, or you might notice it as a smell coming from the mouth itself. It's the same thing. Some owners say their dog's mouth smells like garbage, or metal, or just "off." The description helps, because the smell is a clue to the cause.

Think of it like a kitchen trash can. If the can is cleaned weekly, it smells of very little. If nobody touches it for a month, it smells terrible. Teeth work the same way.

A few things make the smell worse. Small breeds have crowded teeth that trap food. Dry kibble-only diets leave a film behind. Older dogs have had years of plaque to build up. And dogs who never see a toothbrush are on a faster track than dogs who do. Knowing which group your dog falls into tells you how urgent the fix is.

Quick guide: smell, cause and urgency

Causes of dog bad breath, by smell

Periodontal disease and plaque

This is the cause by a wide margin. It's also the one that fits the "terrible", "horrible" or "stinky" breath most owners describe.

Plaque is a soft film of bacteria. It starts forming within hours of eating. If it stays, it hardens into brown tartar in a few days. The bacteria under the tartar inflame the gums, and as the disease advances, they attack the ligaments and bone that hold the tooth in place.

The numbers are large. VCA reports that more than 80 percent of dogs over age three have active dental disease. Small breeds like Yorkies, Chihuahuas and Dachshunds tend to get it earlier. Flat-faced dogs like Pugs and Bulldogs do too, because their teeth are crowded and trap food.

Look for these signs:

• brown or yellow crust along the gumline
• red, swollen gums that bleed when touched
• chewing on one side, or dropping food
• pawing at the mouth or head shaking
• loose or missing teeth

Merck explains that gingivitis (inflamed gums) can be reversed with a good cleaning. Periodontitis, once it reaches the ligaments and bone, can't. That's why catching it early matters.

Urine or ammonia smell: kidney disease

Healthy kidneys filter waste out of the blood. When they fail, urea builds up. Some of it ends up in the saliva, where bacteria break it down into ammonia. The breath then smells like urine or a freshly cleaned bathroom.

The AKC lists a urine-like smell as a sign of kidney disease that needs prompt veterinary care. Other signs include drinking and urinating more than usual, weight loss, vomiting, and ulcers on the gums or tongue. Older dogs are most at risk. A blood and urine test settles the question quickly.

Sweet or fruity smell: diabetes

A sweet smell, like pear drops or nail polish remover, is a different story. It can mean diabetes. When the body can't use sugar properly, it burns fat instead and produces chemicals called ketones. Ketones smell sweet.

Other signs are heavy drinking, frequent urination, weight loss despite a good appetite, and cloudy eyes. Diabetes is very manageable with insulin and diet. But sweet breath with vomiting, weakness or fast breathing can mean diabetic ketoacidosis, which is an emergency. See why dogs vomit for what to watch alongside it.

Foul breath with vomiting and yellow gums: liver disease

The liver clears toxins from the blood. When it can't, those toxins show up in the breath as a foul, musty smell. The AKC links this smell, along with vomiting and loss of appetite, to liver disease.

Check the gums and the whites of the eyes. A yellow tint (jaundice) is a red flag. So is yellow vomit that keeps coming back. Liver disease can follow poisoning or a toxic plant, so tell your vet about anything your dog might have eaten. This is a same-day visit.

Breath that smells like poop

If your dog's breath smells like feces, the likeliest answer is the simplest one. Your dog eats stool. Vets call this coprophagia. It's common in puppies and in dogs who graze on cat litter, goose droppings or their own mess. Rotten garbage does the same thing.

Stool-eating also carries parasites, so mention it at the next checkup. Cleaning up the yard quickly is the simplest fix. Training a solid "leave it" helps too.

Rarely, a feces smell can come from a bowel obstruction. In this case vomiting is the clue. The vomit may smell of feces, and your dog may stop passing stool or strain. That's an emergency. If you see blood in the stool as well, don't wait.

Metallic or blood smell

A smell like pennies or metal is the smell of blood. In the mouth that usually means bleeding gums. Advanced gum disease is the top reason, and tartar can pull the gum away from the tooth so it oozes whenever your dog chews.

Other causes include a cracked tooth, a cut from a bone or stick, or a sore on the tongue or cheek. Lift the lip and look. Pink-red streaks on a chew toy, or a pink tinge in the water bowl, back up the story.

Bleeding that persists, or bleeding with bruising, calls for a vet quickly. Some poisons, including certain rat baits, stop blood from clotting. If your dog may have eaten any, see our poisoning emergencies guide and go now.

Oral tumors in older dogs

An unusually bad smell, like something dead, along with a lump on the gums can signal a tumor. VCA lists tissue death from oral tumors among the causes of halitosis. These growths often bleed easily and can look like a swelling or an overgrown gum.

They're more common in older dogs. Not every lump is cancer. But any lump, any bleeding without an obvious cause, or any loose tooth in an older dog deserves an exam. Early removal gives the best results.

A foreign object stuck in the mouth

Sticks, bone fragments, rawhide, and strings or cloth fibers from a toy can wedge between teeth or across the roof of the mouth. Food packs in around them and starts to rot, and the smell comes on fast.

Signs are sudden. Your dog paws at the mouth, drools, gags or refuses food. If you can see the object and it comes out easily, take it out. If it doesn't, don't pull. Call your vet. If your dog is also gagging, read about coughing and gagging.

What doesn't cause the smell

Some foods smell strong but don't mean illness. Fish-based diets and fish oil give dogs a fishy odor for a few hours. Garlic and onion also smell, but they can be toxic. If your dog ate some, see whether garlic or onions are a risk first.

Remedies you can use at home

You can't fix bad breath with a mint. You fix it by removing what the bacteria feed on.

1. Brush daily. Use a dog toothpaste and a soft brush or a finger brush. Start with a few seconds and add time each day. Merck says gum disease won't develop around clean teeth.
2. Wipe if brushing fails. Gauze wrapped around a finger, wiped over the teeth every two or three days, is better than skipping.
3. Add helpers. Dental chews, water additives and dental diets can slow plaque. Look for the Veterinary Oral Health Council seal, which means the product has passed testing.
4. Skip hard chews. Bones, antlers and hard nylon toys crack teeth. If you can't dent it with your thumbnail, it may be too hard.
5. Keep the trash and yard clean. It sounds obvious, but this is the cure for poop breath.

Home care prevents tartar. It doesn't remove what's already there. Once tartar has formed, it takes a professional scale and polish under anesthesia. VCA notes that this includes cleaning below the gumline and dental X-rays to assess bone damage.

What the vet will do

Your vet will lift the lips, grade the gums and teeth, and ask about drinking, appetite and vomiting. If the mouth looks fine but the smell is odd, expect blood and urine tests to check the kidneys, liver and blood sugar.

For dental disease, the usual plan is a cleaning under anesthesia. Loose or badly infected teeth are removed. A dog that has had a thorough cleaning often smells better the same week, and gets back to eating more comfortably.

When to call the vet

Call within a day or two if the smell is new, strong or changing. Go the same day if the breath comes with vomiting, yellow gums, sweet fruity odor with heavy thirst, a bleeding mouth that won't stop, or a dog that can't or won't eat.

If your dog is a young puppy, the causes are different. See puppy bad breath. For the full picture on dental care, visit the Dental and Bad Breath hub.