Dog Bad Breath: Causes and What to Do About It

"Dog breath" sounds like something you just have to live with. But genuinely bad or foul-smelling breath in a dog is almost always a medical issue — and almost always a treatable one.

The Most Common Cause: Periodontal Disease

Over 80% of dogs over 3 years old have some degree of periodontal disease — plaque and tartar accumulation, gum inflammation (gingivitis) and infection of the tooth-supporting structures (periodontitis). The bacteria in these deposits produce volatile sulphur compounds that create the characteristic odour.

Associated signs: red or swollen gums, visibly brown or grey teeth, pain or reluctance when eating, loose or lost teeth.

Other Causes of Bad Breath

• Foreign body: A splinter, bone fragment or piece of toy lodged between teeth or in the gum. Sudden-onset smell, dog may paw at mouth.
• Oral tumour: Melanoma, squamous cell carcinoma and fibrosarcoma can all produce foul odour through tissue necrosis. Any visible mass in the mouth warrants prompt veterinary assessment.
• Kidney failure: Uraemic or ammonia-like breath can be a sign of elevated blood urea (uraemia). A serious systemic warning.
• Uncontrolled diabetes: Sweet, fruity or acetone-like breath.
• Gastrointestinal issues: Acid reflux, megaoesophagus or malabsorption can contribute to bad breath.
• Coprophagia: If the dog eats faeces, the smell can persist for hours.

What to Do

If the Cause Is Dental (Most Likely)

1. Dental examination under anaesthesia: The only way to properly assess every tooth surface, including below the gum line. Professional scaling removes subgingival tartar that no toothbrush can reach.
2. Brushing at home: The most effective preventive measure. Dog toothbrush and dog-specific toothpaste (never human toothpaste — fluoride is toxic to dogs). Introduce gradually; aim for daily.
3. Supplements: Dental chews, dental toys, dental diets (e.g. Hills t/d) or water additives can complement brushing — but none replace it.

If the Smell Is Sudden or Unusual

Ammonia or urine-like smell, sweet/acetone smell, or a putrid odour that appeared suddenly: see the vet the same day. These can signal serious systemic disease.

Prevention

• Brush teeth 3–7 times a week — ideally daily — starting in puppyhood
• Annual dental check with the vet
• Professional dental cleaning every 1–2 years in dogs prone to tartar