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Why Does My Dog Have Bad Breath? Causes and What to Do

Bad breath (halitosis) in dogs is common but not normal. While many owners accept it as inevitable, persistent bad breath almost always has a treatable cause — and sometimes it's a sign of something more serious than just dental plaque. Here's what's most likely going on.

Dental Disease: The Primary Cause

By the age of three, around 80% of dogs in the UK have some degree of periodontal disease — the same RCVS data cited by the British Veterinary Dental Association. Plaque builds on teeth, hardens into tartar, and harbours bacteria that cause the characteristic bad smell of poor dental hygiene, alongside gum inflammation and eventual tooth loss.

The smell of dental disease in dogs has been described as a sour, slightly faecal odour. It often worsens as the disease progresses. Alongside bad breath, signs of dental disease include reluctance to eat hard food, pawing at the mouth, red or bleeding gums, visible tartar (yellow-brown deposits), and loose or missing teeth.

Dental scale and polish under general anaesthetic is the treatment for established dental disease, costing £150–£400 at UK practices. Prevention — daily tooth brushing using dog-specific enzymatic toothpaste — is far cheaper and significantly reduces the need for anaesthetic dental procedures.

Dietary Causes

What your dog eats significantly affects the smell of their breath. Dogs that scavenge, eat faeces (coprophagia — common in dogs and deeply unpleasant for owners), eat dead animals or strongly smelling food will have correspondingly unpleasant breath that resolves once the dietary source is removed.

Coprophagia can be a normal behaviour in dogs, particularly puppies, but may also indicate nutritional deficiency, attention-seeking, or anxiety. If your dog is eating their own faeces regularly, speak to your vet — it may indicate a digestive issue.

Some dogs have bacterial overgrowth in the gastrointestinal tract or digest particularly malodorous foods (raw fish, certain proteins) that produce aromatic compounds absorbed and exhaled through the breath. A dietary change or probiotic may help in these cases.

When Bad Breath Indicates a Systemic Condition

Certain smells from a dog's breath carry specific diagnostic significance. A sweet or fruity smell — sometimes described as similar to nail polish remover — can indicate ketoacidosis, associated with uncontrolled diabetes mellitus. This is a medical emergency if accompanied by lethargy, vomiting and not eating.

A urine-like or ammonia smell from the breath can indicate kidney failure — waste products that the kidneys are failing to filter accumulate in the blood and are exhaled. This is a serious sign requiring urgent investigation.

Liver disease can produce a musty, sweet breath odour. Mouth ulcers, abscesses, foreign objects lodged in the gum, or oral tumours can also cause severe halitosis from the affected site.

Preventing Bad Breath Through Dental Care

Daily tooth brushing is the gold standard for preventing dental disease and associated bad breath. Use a toothbrush designed for dogs (or a finger brush) with enzymatic canine toothpaste — never human toothpaste, which is toxic due to xylitol or fluoride in concentrations unsuitable for dogs.

Dental chews, water additives, dental diets and specifically designed toys can supplement but not replace brushing. The Veterinary Oral Health Council (VOHC) seal of acceptance on a product indicates evidence-based efficacy for reducing plaque and tartar.

Start dental hygiene routines early — ideally from puppyhood — when dogs are most receptive to having their mouths handled. Adult dogs can be trained to tolerate brushing with patience and positive reinforcement, though it takes longer.

When to See a Vet About Bad Breath

Any sudden change in breath odour, particularly to a distinctive sweet, ammonia or urine-like smell, warrants prompt veterinary attention to rule out systemic disease. Established bad breath that has been present for some time without these distinctive odours is most likely dental and should be assessed at your next vet visit.

Annual dental checks are recommended by the British Veterinary Dental Association. Many practices offer free nurse checks specifically for dental assessment — ask about this when booking your dog's annual vaccination.

If dental treatment is needed, ask for a written cost estimate in advance, as required by CMA 2026 reforms for treatments over £500. Scale and polish costs vary considerably between practices — comparing prices using CompareMyVet is a practical way to manage this cost.

Find a Vet Near You

Dental care is one of the most frequently needed but most underprovided aspects of dog healthcare. Use CompareMyVet at app.comparemyvet.uk to find and compare vet practices near you, including dental treatment costs, so you can plan ahead.