Why Does My Dog's Breath Smell?

Bad breath in dogs is often the first sign of dental disease. Bacteria in plaque on the teeth give off sulfur gases, and that's the smell. A dog breath freshener can cover it for a while. Cleaning the teeth deals with the cause.

Start with a vet check, because the right next step depends on what's under the gumline. Breath that's suddenly much worse, or that comes with drooling or trouble eating, needs a vet sooner.

The good news is that the earliest stage is reversible. Here's what's behind the smell, what fresheners can and can't do, and what actually helps.

What causes bad breath in dogs?

Cornell's Riney Canine Health Center puts it simply: bad breath (halitosis) is often the first thing people notice when their dog has dental disease.

The disease in question is usually periodontal disease, or gum disease. AAHA's dental guidelines call it the most common and significant disease of the mouth in dogs and cats.

It starts young. The Merck Veterinary Manual reports that up to 80% of dogs have some level of periodontal disease by age 2.

It starts with plaque, a film of bacteria on the teeth. The first stage is gingivitis, where only the gums are inflamed. Left alone, plaque hardens into tartar (calculus) and the damage can reach the ligaments and bone that hold each tooth.

So what is the smell, exactly?

Here's the part most people don't expect. The odor is a gas, made by the bacteria themselves.

A 2023 study in Veterinary Sciences looked at Porphyromonas bacteria taken from dogs' mouths. They produce volatile sulfur compounds, including hydrogen sulfide, the gas behind the smell of rotten eggs, and methyl mercaptan.

The bacteria make these gases by breaking down sulfur-containing amino acids. The same compounds can also damage gum tissue, the authors note, which is why the smell and the gum problem tend to travel together.

Size plays a part too. Merck notes that small-breed dogs usually have more problems with periodontitis, the advanced stage, than large breeds. Toy breeds appear on its list of risk factors.

Can bad breath mean something other than teeth?

Sometimes. Merck's guide to mouth disorders in dogs lists several other causes worth knowing:

• Inflammation of the mouth or tongue. Bad breath and drooling are common with both.
• Something caught in the mouth. A thread, string or plant material can lodge under the tongue, and a long-standing case can give off a foul-smelling discharge.
• Inflamed lip folds. Dogs with this may paw or rub at their lips and have a foul odor on the breath.
• Growths in the mouth. With oral tumors, bad breath, reluctance to eat and drooling are common.
• Kidney trouble. Merck notes that chronic kidney failure can cause inflammation and sores in the mouth.

You can't tell these apart by smell at home, and you don't need to. A vet can look in the mouth and work out the cause.

Do dog breath fresheners work?

They can make breath smell better for a while. The useful question is whether a product does anything about the plaque that makes the smell.

That's where the Veterinary Oral Health Council (VOHC) comes in. Its panel of veterinary dentists and dental scientists reviews company data and awards a Seal of Acceptance for plaque control, tartar control, or both.

Here's an interesting detail. The VOHC reviews plaque and tartar claims, and its seal doesn't rate breath. Several water additives with "fresh breath" in their names are on its list, and their accepted claim is plaque.

AAHA's guidelines say that although many products claim to slow plaque and tartar, only VOHC-accepted ones have met preset standards. The VOHC's accepted products list is the place to check a chew, diet or water additive before you buy.

Never use a breath freshener made for people

This one matters. The ASPCA lists toothpaste, mouthwash, mints and breath fresheners among the products that can contain xylitol, a sweetener that is dangerous to dogs.

According to the ASPCA, xylitol can drop a dog's blood sugar within 30 minutes, though signs can take up to 12 hours to show. Weakness, unsteadiness and shaking are early signs. If your dog eats something with xylitol in it, call your vet right away.

What actually freshens a dog's breath?

Removing plaque. Every source here agrees on that, and the first step is a vet exam, so you know whether the gums are healthy enough for home care.

Brushing

Cornell calls brushing the most effective home care there is. AAHA's guidelines say it needs to be done daily to be of benefit, and that brushing removes plaque, not tartar that has already hardened.

One caution from the same guidelines: brushing gums that are already inflamed causes pain, and can turn a dog against the toothbrush. That's another reason the vet visit comes first.

Don't worry if daily brushing feels out of reach at first. The VOHC and the American Veterinary Dental College note that any brushing done regularly is better than none.

They also share a useful tip. Plaque and tartar build up fastest on the cheek side of the upper teeth, so give those surfaces extra attention. Our guide on how to brush a dog's teeth walks through it step by step.

Chews, diets and additives

Merck lists dental diets, chews, toys, oral gels, rinses, sprays, and water and food additives as home-care options. AAHA notes that dental diets are especially helpful if you can't brush.

Pick chews carefully. AAHA's task force sees no strong reason to offer very hard chews such as antlers or bones, which can break teeth. Our guide to safe chews for dogs covers what to look for.

Professional cleaning

Once tartar has formed, brushing won't remove it. Merck notes that gingivitis can usually be addressed with a thorough professional cleaning under anesthesia, and that removing plaque can return the gums to a healthy state.

You may see "anesthesia-free" cleaning offered. AAHA calls it unacceptable. It cleans only the visible surface, can't reach below the gumline, and gives what the guidelines call a false sense of benefit.

Merck agrees that cleaning an awake animal improves how the teeth look, but does not improve gum health.

Call your vet promptly if your dog has:

• bad breath that's new, or getting worse
• trouble eating, or less interest in food
• bleeding from the mouth
• swelling of the jaw or face
• drooling, or pawing at the mouth
• nasal discharge
• eaten gum, mints or anything else that may contain xylitol (call right away)

Questions dog parents ask

Is bad breath in dogs normal?

It's common, but it's worth a check. Cornell lists bad breath among the signs to contact your vet about, since it's often the first sign of dental disease.

Can I give my dog breath mints?

Not mints made for people. The ASPCA lists mints and breath fresheners among products that can contain xylitol, which is dangerous to dogs.

Do water additives freshen a dog's breath?

Some carry the VOHC seal, and their accepted claim is plaque control. The seal doesn't rate breath, so read it as a plaque result.

Is anesthesia-free teeth cleaning safe for dogs?

AAHA's dental guidelines call it unacceptable. It can't clean below the gumline or allow a full exam, so problems can go unnoticed.

How often should my dog's teeth be checked?

Cornell says vets look in the mouth at annual visits, and may check more often based on your dog's age, breed, dental health and medical history.

Sources

• Cornell Riney Canine Health Center: Dental Disease and Home Dental Care
• Bellows J et al. 2019 AAHA Dental Care Guidelines for Dogs and Cats. JAAHA, 2019
• Merck Veterinary Manual: Periodontal Disease in Small Animals
• Merck Veterinary Manual: Dental Disorders of Dogs
• Merck Veterinary Manual: Disorders of the Mouth in Dogs
• Ito N, Itoh N, Kameshima S. Volatile Sulfur Compounds Produced by the Anaerobic Bacteria Porphyromonas spp. Isolated from the Oral Cavities of Dogs. Veterinary Sciences, 2023
• Veterinary Oral Health Council
• VOHC: Accepted Products
• VOHC: Brushing
• ASPCA: Xylitol, a sweetener that's not so sweet for pets

This article is for general information and is not veterinary advice. Talk to your vet about your own dog — they know the animal in front of them.

Choolip products are food supplements, not medicine. They are not intended to diagnose or manage any medical condition. If your dog has been diagnosed with a condition, their diet should be set by your vet.