Symptom guide

Why Does My Dog Have Bad Breath? Causes and Fixes

Most bad breath in dogs comes from dental disease. What different smells can point to, when bad breath means illness, and how to keep your dog's mouth healthy.

Updated October 2026 · 6 min read · By the Hushku editorial team · 1 sources

Book a routine vet visit. Book a check-up; sooner if your dog is unwell

Short answer

Bad breath in dogs is almost always caused by dental disease: plaque bacteria and tartar build-up along the gumline. A vet check and, usually, a dental cleaning under anaesthesia fixes it, and daily tooth brushing keeps it away. Breath that smells sweet or fruity, or of urine, can be a sign of diabetes or kidney disease and needs a vet soon.

Key facts

Most bad breath in dogs comes from dental disease.
Most dogs have some periodontal disease by age 3.
Sweet or fruity breath can signal diabetes; urine-smelling breath, kidney disease.
Look for the VOHC seal on dental chews and products.

This guide is general information, not a diagnosis. If your pet seems unwell, or you're worried, call your vet.

Overview

"Dog breath" isn't normal. A healthy dog's mouth shouldn't smell strongly, and persistent bad breath (halitosis) is usually the first sign of periodontal disease, which affects most dogs by the age of three, according to the American Animal Hospital Association.

Plaque, a film of bacteria, forms on teeth within hours of a meal. If it isn't removed, it hardens into tartar within days, and bacteria spread under the gumline, where they cause inflammation, pain, gum recession and eventually tooth loss. The smell comes from the sulphur compounds those bacteria produce.

Most of the disease is hidden below the gums, so a mouth that looks fairly clean can still be sore. Dogs rarely show dental pain; many keep eating normally even with infected teeth.

Go to a vet now if you see

Sweet or fruity breath with heavy drinking, vomiting or lethargy (possible diabetic ketoacidosis)
Facial swelling, a swelling under the eye, or your dog refusing to eat
Bleeding from the mouth that won't stop
Breath that smells of urine with vomiting or weakness

Common causes

1. Periodontal (gum) disease
Needs a vet
By far the most common cause. Look for yellow-brown tartar, red or bleeding gums, and drooling or pawing at the mouth.
2. Broken or infected teeth
Needs a vet
Fractured teeth from chewing bones, antlers or hard toys can become infected and abscess. A swelling under the eye can be a tooth root abscess.
3. Something stuck in the mouth
Usually mild
Sticks, bone fragments or grass caught between teeth or across the roof of the mouth can cause a sudden, foul smell.
4. Eating faeces or rubbish
Usually mild
Dogs that eat poop, carrion or rubbish often have unpleasant breath for a while afterwards.
5. Diabetes
Serious
A sweet or fruity smell, with drinking and peeing more, can be a sign of diabetes with ketones, which needs prompt treatment.
6. Kidney disease
Serious
Breath that smells of urine or ammonia, with increased thirst, weight loss or vomiting, can mean the kidneys aren't clearing waste.
7. Oral tumours
Serious
Growths in the mouth, more common in older dogs, can bleed and smell. Any lump in the mouth should be checked.

What you can do at home

Lift your dog's lips and look at the back teeth, which usually have the most tartar.
Start daily tooth brushing with a soft brush and dog toothpaste; see our step-by-step guide.
Choose dental chews and diets with the Veterinary Oral Health Council (VOHC) seal, which have been tested to reduce plaque or tartar.
Avoid very hard chews (antlers, bones, hooves) that commonly break teeth. If you can't bend it or dent it with a fingernail, it's too hard.
Never use human toothpaste, which can contain xylitol and fluoride.

When to see a vet

Bad breath that lasts more than a few days
Visible tartar, red gums, loose or broken teeth
Drooling, pawing at the mouth, chewing on one side or dropping food
Any lump or ulcer in the mouth
Bad breath with drinking more, weight loss or vomiting

Prevention

Brush your dog's teeth daily, or at least several times a week
Have a dental check at every annual vet visit
Book professional cleanings under anaesthesia when your vet recommends them
Small and flat-faced breeds are especially prone to dental disease, so start brushing early

Free tools for this

Dog and cat symptom checker

Sources

AAHA: 2019 Dental Care Guidelines for Dogs and Cats

We check guides against veterinary sources and update them when guidance changes. How we write and review.

Questions.

Is anaesthesia-free dental cleaning OK?

AAHA advises against it. Scraping tartar off the visible tooth surfaces doesn't treat disease below the gumline, can't include X-rays, and can be stressful and painful. A proper cleaning needs anaesthesia.

Do water additives and dental chews work?

Some do. Look for the VOHC seal, which means the product has been tested. They help alongside brushing but don't replace it or treat existing disease.

Why does my puppy's breath smell?

Puppy breath is often linked to teething, as baby teeth fall out and adult teeth come through between about 3 and 7 months. A truly foul smell should be checked.

Key facts

Overview

Go to a vet now if you see

Common causes

1. Periodontal (gum) disease

2. Broken or infected teeth

3. Something stuck in the mouth

4. Eating faeces or rubbish

5. Diabetes

6. Kidney disease

7. Oral tumours