Bad breath in dogs

photo of dog on white background


It’s common to assume bad breath is always due to dental disease. Dental disease is a very common cause of bad breath but it can also be caused by some more serious health problems such as kidney disease, liver disease, lung disease, and gut problems.

Bad breath isn’t normal and should always be investigated by a vet to see what’s causing it.

Book an appointment with your vet if your dog has bad breath and make it as soon as possible if they seem unwell.

Causes of bad breath

Tooth and gum disease

Tooth and gum diseases such as plaque, tartar, infections, sore gums or abscesses very often cause bad breath.

Kidney disease

Kidney disease causes waste products to build up in the body. This can cause your dog’s breath to smell like ammonia (similar to bleach).


Some diets can cause a dog’s breath to be smellier than others. Fish based diets can cause a fishy smelling breath.

Liver disease

Liver disease leads to the body’s waste products being breathed out from the lungs. This causes a foul, sweet, musty breath.

Things stuck in the mouth

If something gets stuck in your dog’s mouth or throat (a stick, bone or part of a toy for example) it will often cause an infection or start to rot and smell. You may also notice your dog pawing at their mouth or face.

Airway infections

Bacterial infections in the lungs, sinuses or windpipe can cause can cause bad breath.


If diabetes isn’t properly managed the body starts to break down fat, this causes the breath to smell sweet (similar to pear drops or nail polish remover).

Gut problems

A gut infection or blockage will often make the breath smell bad. You will often notice other signs such as diarrhoea, vomiting or stomach pain before noticing bad breath.

Mouth cancers

Cancers in the mouth often become infected and start to smell. Your vet may need to put your dog under anaesthetic or sedate them to look properly in their mouth. Cancers in this area can be difficult to treat but finding them early can help.

When to contact your vet

If you notice a change in your dog’s breath, make an appointment with your vet. They will be able to investigate what is causing the problem and start treatment.

Published: October 2018

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Written by vets and vet nurses. This advice is for UK pets only.

Illustrations by Samantha Elmhurst