Why Does My Dog Have Bad Breath?
By Dr Joe Inglis BVSc MRCVS ·
The most common reason for bad breath in dogs is dental disease, especially periodontal disease, which is the most frequently diagnosed health problem in UK dogs. Less often, bad breath can be caused by something stuck in the mouth, a broken or infected tooth, or a health problem elsewhere in the body. Bad breath isn't something to ignore or simply mask. This guide explains the common causes, the signs to look out for, and when your dog should see a vet.
Is bad breath normal in dogs?
No. Many owners assume "dog breath" is just part of having a dog, but a healthy dog's breath should not smell strongly or unpleasantly. Their breath may briefly smell of whatever they've just eaten, but it shouldn't have a persistent foul odour.
The medical term for bad breath is halitosis. In dogs, it is most often caused by bacteria in the mouth producing smelly sulphur compounds. These bacteria thrive in plaque, tartar and infected gum pockets, so ongoing bad breath is usually a sign that something in the mouth needs attention.
The one common exception is a puppy's breath, which can smell different while baby teeth are falling out and adult teeth are coming through, between roughly 3 and 7 months of age.
What causes bad breath in dogs?
Dental disease
Dental disease is by far the most common cause of bad breath in dogs. Plaque bacteria build up on the teeth and harden into tartar, and infection spreads below the gumline. This is called periodontal disease, and it affects around 1 in 8 UK dogs seen by vets each year (RVC VetCompass). The deeper the infection, the stronger the smell tends to be. Read more about periodontal disease
Broken teeth and abscesses
A fractured tooth can expose the sensitive pulp inside, allowing bacteria in. Infection can then spread to the tip of the root and form an abscess, which often produces a foul smell and sometimes swelling on the face below the eye.
Something stuck in the mouth
Sticks, bone fragments, grass seeds and bits of chew can become wedged between teeth, across the roof of the mouth, or in the gums. These quickly become infected and smelly. Signs include sudden bad breath, pawing at the mouth, drooling or difficulty eating.
Oral tumours
Growths in the mouth are less common, but they can cause bad breath, particularly if they become ulcerated or infected. Lumps, bleeding, loose teeth in one area, or swelling of the jaw should always be checked promptly.
Lip fold infections
Dogs with deep folds of skin around their lower lips, such as Spaniels, can develop infections in those folds. The smell can be mistaken for bad breath, even though the teeth may be healthy.
Diet and scavenging
Eating faeces, rubbish or dead animals can cause temporary bad breath. Persistent eating of faeces (coprophagia) is worth discussing with your vet. Diet alone rarely causes long-term bad breath.
Other health conditions
Occasionally, bad breath is a sign of illness elsewhere in the body:
- Kidney disease can give breath an ammonia or urine-like smell, often with increased thirst, weight loss or vomiting.
- Diabetes can cause sweet or fruity-smelling breath. Combined with weakness, vomiting or not eating, this can indicate a serious complication that needs urgent veterinary care.
- Liver disease can cause unusually foul breath, often with vomiting, poor appetite or yellowing of the gums and eyes.
- Nasal and sinus problems can cause a smell along with nasal discharge or sneezing.
Other signs to check for
If your dog has bad breath, lift their lips and take a look. Check the back teeth too, as this is where tartar and disease are often worst. Signs that point to a dental cause include:
- Yellow or brown tartar on the teeth
- Red, swollen or bleeding gums
- Receding gums or exposed roots
- Broken, worn or discoloured teeth
- Loose or missing teeth
- Swelling on the face or jaw
- Lumps or growths in the mouth
- Drooling, or saliva tinged with blood
- Chewing on one side, dropping food or avoiding hard food
An initial scan with the Luna AI dental photo check can help identify any obvious dental issues that might be contributing to bad breath. Other signs that suggest a wider health problem include increased thirst, drinking or urinating more, weight loss, vomiting, lethargy or a change in appetite. If you notice any of these alongside bad breath, contact your vet promptly.
Remember that many dogs with dental disease show no obvious signs at all, apart from bad breath.
How is the cause of bad breath diagnosed?
Finding the cause usually follows three or four steps:
- Dental photo assessment. If you are able to take clear photos of your dog’s teeth, the Luna AI photo check can provide useful feedback on any obvious signs of dental issues that could be contributing to your dog’s bad breath.
- Vet health check. Your vet will ask when the smell started, whether it's getting worse, and about your dog's eating, drinking and general health. They will also check your dog over from nose to tail.
- Conscious mouth examination. Looking at the teeth, gums, tongue, palate and lips shows visible problems such as tartar, gum disease, broken teeth, foreign objects, lip fold infections and growths.
- Further tests, if needed. If the mouth looks healthy, or if your dog has other symptoms, your vet may recommend blood and urine tests to check for conditions such as kidney disease, diabetes or liver disease.
When dental disease is the cause, a full assessment needs a general anaesthetic. This allows the vet to probe around every tooth and take full-mouth dental X-rays, which show disease below the gumline that can't otherwise be seen.
How is bad breath in dogs treated?
Treatment depends on the cause. The aim is always to fix the underlying problem, not just the smell.
For dental disease, the most common cause, treatment is a dental procedure under general anaesthetic. This usually includes:
- Full examination, probing and dental X-rays of every tooth
- Scaling above and below the gumline to remove plaque, tartar and bacteria
- Polishing to smooth the teeth and slow plaque build-up
- Extraction of teeth that are too damaged or infected to save
- Pain relief, and in some cases antibiotics
Most owners notice a dramatic improvement in their dog's breath after treatment, and often in their dog's energy and mood too.
For other causes, treatment might include removing a stuck object, treating a lip fold infection, investigating a growth, or managing an underlying condition such as kidney disease or diabetes.
Antibiotics on their own are not a treatment for dental disease. They may reduce the smell for a short time, but the bacteria return quickly unless plaque and tartar are removed.
Do breath fresheners, chews and sprays work?
It depends on what they're designed to do. Products that simply mask the smell, such as minty treats or breath sprays, don't treat the cause. If your dog has dental disease, masking the odour can hide a painful problem and delay treatment.
Products that reduce plaque can genuinely help keep breath fresher, but only as part of a routine that includes regular checks and, ideally, daily brushing. These include:
- Dental chews designed to clean the teeth as your dog chews
- Dental diets with a kibble texture that wipes the tooth surface
- Water additives, gels and supplements that help reduce plaque bacteria
One important point: no chew, spray or supplement can remove existing tartar or treat disease below the gumline. If your dog already has bad breath, a vet check should come first. Once any disease has been treated, these products are a useful way to help keep the mouth healthy.
How can I prevent bad breath in my dog?
As most bad breath comes from dental disease, the best prevention is keeping your dog's mouth healthy:
- Brush your dog's teeth daily with a soft brush and dog toothpaste. This is the single most effective way to control the plaque bacteria that cause bad breath.
- Start young, getting puppies used to having their mouths handled.
- Use evidence-based dental products such as Luna Plaque Protect supplement, dental chews or diets, alongside brushing.
- Avoid very hard chews, such as bones and antlers, which can break teeth.
- Keep your dog away from rubbish and faeces where possible.
- Book regular dental checks, every 6 months, and more often for small breeds and older dogs.
- Act on changes early. If your dog's breath gets worse, don't wait for their next routine check.
When should I see a vet about my dog's bad breath?
Contact a vet urgently if your dog's bad breath comes with:
- A sweet or fruity smell plus weakness, vomiting or not eating
- Vomiting, lethargy or yellowing of the gums or eyes
- Facial swelling, or a swelling or wound below the eye
- Bleeding from the mouth
- Sudden difficulty eating, or pawing at the mouth
Book a dental check if:
- Your dog's breath has smelled bad for more than a week or two
- You can see tartar, red gums or broken teeth
- The smell is getting worse over time
- Your dog is a small breed or older dog and hasn't had a dental check in the last year
Bad breath is often the first and only sign of dental disease that owners notice, so it's always worth getting checked.
How Luna can help
Luna the Dental Vets is a UK veterinary practice group dedicated entirely to dentistry for dogs and cats. Bad breath is one of the most common reasons owners bring their dogs to us, and in most cases we can find and treat the cause.
When your dog visits Luna, you can expect:
- A dental health check to look for the cause of the smell and explain what we find
- Full-mouth dental X-rays as standard with every dental procedure
- Detailed charting of every tooth, so you know exactly what was found and treated
- Careful anaesthesia and monitoring, with pain relief tailored to your dog
- Clear home-care advice to help keep your dog's breath fresh after treatment
- Bespoke care packages through the Luna Dental Health Club
We have clinics in Bristol, Reading and Eastleigh, with Surbiton opening soon, and we welcome both direct bookings from owners and referrals from your regular vet.