Dog Bad Breath: What Causes It and What Actually Helps
Last reviewed: August 2026
Most bad breath is periodontal disease
Not diet, and not something a breath mint fixes. Most dogs show some degree of periodontal disease by age three, and the smell comes from bacteria below the gumline.
Has your dog had recent bloodwork?
Kidney and liver values can explain breath changes that have nothing to do with teeth. Upload a panel to see what your dog's numbers say.
Check My Dog's Bloodwork"Dog breath" gets treated as normal, and mild odour after a nap usually is. But breath that clears a room is not a quirk of being a dog — it is nearly always a symptom, and in most cases the cause is treatable.
What Causes Bad Breath in Dogs
Periodontal disease
The most common cause by a wide margin. Bacteria in plaque below the gumline release volatile sulphur compounds — the classic rotten smell.
Anal glands
The usual explanation for genuinely fishy breath. Dogs lick the area when the glands are full, and the smell transfers to the mouth.
Kidney disease
Breath that smells of ammonia or urine can mean the kidneys are struggling to clear waste. This one needs bloodwork, not a dental.
Diabetes
Sweet or fruity breath can signal diabetic ketoacidosis. Combined with drinking and urinating more, treat it as an emergency.
Puppy teething
Mildly odd breath between three and seven months is usually retained baby teeth and inflamed gums. It resolves, but retained teeth may need removing.
Something stuck
A stick fragment or bone lodged against the gum causes sudden, severe odour, often with drooling or pawing at the mouth.
What the Smell Tells You
Rotten or foul
Periodontal disease. Book a dental exam.
Fishy
Usually anal glands. Check for scooting or licking at the rear.
Ammonia or urine
Possible kidney disease. Needs bloodwork.
Sweet or fruity
Possible diabetic ketoacidosis. Treat as an emergency.
| Smell | Likely cause | What to do |
|---|---|---|
| Rotten, foul | Periodontal disease | Dental exam |
| Fishy | Anal glands | Check glands, look for scooting |
| Ammonia, urine | Kidney disease | Bloodwork |
| Sweet, fruity | Diabetic ketoacidosis | Emergency vet |
What Actually Helps
The honest answer is that it depends entirely on the cause, and the most common cause needs a vet. Tartar below the gumline cannot be brushed, chewed, or supplemented away — it is removed under anaesthetic during a dental cleaning. Anything else is maintenance for afterwards.
Once the underlying cause is dealt with, these are what the evidence supports:
- • Daily brushing — the single most effective thing you can do at home. Every other day still helps.
- • VOHC-accepted chews — the Veterinary Oral Health Council publishes a list of products with demonstrated plaque or tartar control. Look for the seal rather than the marketing.
- • Water additives and dental diets — modest effects, useful as an addition rather than a replacement.
- • Routine dental cleanings — how often depends on the dog. Small breeds usually need them more.
What does not work: covering the smell. Breath sprays and mints mask odour for minutes without touching the bacteria producing it, and a dog whose breath needs masking usually needs an exam.
Fresh Breath, From the Gut Up
Better Dailies includes EpiCor® postbiotic, which promotes fresh breath and supports gut health and natural immune defenses. A daily air-dried beef chew — maintenance alongside dental care, not a replacement for it.
Shop Better Dailies →
Made by the team behind VetLens.
When to See a Vet
Book an appointment if you notice any of these alongside the smell:
- • A sudden change in how your dog's breath smells
- • Drooling, pawing at the mouth, or dropping food
- • Bleeding gums, or gums that look red and swollen at the tooth line
- • Eating on one side, or going off hard food
- • Drinking or urinating more than usual
- • Weight loss, lethargy, or vomiting
Key Takeaway
Bad breath is a symptom, not a personality trait. Most of the time it is periodontal disease and a dental cleaning fixes it. The exceptions — ammonia, sweet, or a sudden change — point somewhere else and are worth acting on quickly. Chews, brushing and supplements keep things good once they are good; they do not get you there.
Related Reading
Frequently Asked Questions
Why does my dog's breath smell so bad?
Most often periodontal disease — bacteria in plaque below the gumline producing volatile sulphur compounds. Most dogs show some degree of it by age three. Less commonly it points to kidney disease, diabetes, liver disease, or something lodged in the mouth.
Why does my dog's breath smell like fish?
Usually the anal glands rather than the mouth. Dogs lick the area when the glands are full or impacted and the smell transfers. If your dog is also scooting or licking at the rear, have the glands checked.
Can bad breath be a sign of illness?
Yes. Ammonia-like breath can indicate kidney disease, and sweet or fruity breath can indicate diabetic ketoacidosis, which is an emergency. Any sudden change is worth a vet visit.
Do dental chews and supplements fix bad breath?
They help manage plaque between cleanings but do not treat existing periodontal disease. Tartar below the gumline only comes off during a veterinary dental. Think of chews and supplements as maintenance rather than treatment.
Not sure if it's teeth or something else?
Kidney and liver values explain a lot of breath changes that have nothing to do with the mouth. Upload your dog's bloodwork and see what the numbers say.
Analyse My Dog's Bloodwork