Halitosis in a Cat — When Bad Breath Goes Way Beyond "Fishy"

Breath that smells this bad is usually the result of a bacterial infection, which happens when tissue is damaged and bacteria invade.

By: quinn.anya
The most obvious sign of halitosis in a cat is — you guessed it — bad breath. But we’re talking really bad breath here. By: quinn.anya

The word “halitosis” refers to bad breath, but this is about much more than fishy breath — this is an offensive smell caused by disease.

The bad smell is usually the result of a bacterial infection that happens when tissue is damaged and bacteria invade. Although halitosis can happen because of general disease (i.e., kidney failure and diabetes), it most commonly results from mouth problems including dental or gum-health issues, an oral foreign body or cancer affecting the tongue or gums.

In the short term, getting rid of the smell requires antibiotics, but to stop halitosis from returning, vets must look beyond the obvious and find the underlying cause.


The most obvious symptom of halitosis in a cat is bad breath, the sort that makes you turn away when your cat breathes on you.

But other signs include pain when the cat eats, such that it makes him cautious about eating — which may lead to weight loss. If the mouth is very inflamed, the cat may drool blood-tinged saliva; he also may be too sore to groom, so his coat becomes unkempt, dull and matted.

When the cat does manage to groom, his coat may start to smell unpleasant because he is spreading smelly saliva all over the fur. Some cats show slightly bizarre signs such as gulping a lot or coughing.


The underlying causes that allow infection to take hold in the mouth are:

  • Dental calculus — tartar deposits that build up on the teeth and cause the gums to recede
  • Gingivitis or stomatitis — inflammation of the gums, usually where the teeth meet the gums, but it can happen anywhere along the gum line, even in the absence of teeth; this is a complex condition with many possible causes such as a suppressed immune system, infection by the Calici virus or dirty teeth that harbor high levels of bacteria
  • Oral cancer — cancerous lumps can grow rapidly, becoming ulcerated and infected, leading to a bad smell
  • Tongue lacerations or ulcers — some cats cut their tongues on tin cans and a nasty infection can result, but happily, these usually respond well to a little TLC, a soft diet and a course of antibiotics
  • Oral foreign body — the most common oral foreign body is a grass blade; the cat chews grass, but instead of getting cleanly swallowed, the grass blade gets diverted to the back of the throat, where it becomes lodged and traps food


The cause of bad breath can usually be identified by a thorough inspection of the mouth. However, if the mouth is very painful, a general anesthetic may be necessary to allow a full oral exam, especially right to the back of the throat.

An anesthetic has the added advantage of enabling further investigation at the same time as the exam, such as dental X-rays or a biopsy of any suspicious lumps and bumps should they be indicated.

Treating a Cat With Halitosis

A course of an antibiotic effective against the common bacteria found in the mouth helps get rid of the smell.

However, a thorough investigation may reveal an underlying problem that needs remediation, such as removing grass blades from the back of the throat, cleaning teeth or instigating treatments for gingivitis or stomatitis.

For more about bad breath in pets, check out the video below:


Good oral hygiene plays an important role in decreasing the chances of dental disease and gingivitis.

The gold standard is daily tooth brushing, but if your cat is not keen on this idea, try feeding a little kibble with teeth-cleaning properties.


  • Small Animal Clinical Oncology. Withrow & MacEwen. Publisher: WB Saunders. 2nd edition.
  • Textbook of Feline Medicine. Publisher: Pergamon Press.


This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Nov. 18, 2014.

Dr. Pippa Elliott, BVMS, MRCVS

View posts by Dr. Pippa Elliott, BVMS, MRCVS
Dr. Pippa Elliott, BVMS, MRCVS, is a veterinarian with nearly 30 years of experience in companion animal practice. Dr. Elliott earned her Bachelor of Veterinary Medicine and Surgery from the University of Glasgow. She was also designated a Member of the Royal College of Veterinary Surgeons. Married with 2 grown-up kids, Dr. Elliott has a naughty puggle called Poggle, 3 cats and a bearded dragon.

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