Halitosis – bad breath in Cats

Cat breath is rarely meant to be “just a cat thing”. When it turns sour, metallic, sweet, or simply strong enough to notice across the room, it’s often the first sign that something in the mouth (or elsewhere in the body) needs attention.

Most cases come back to dental disease: plaque, tartar, and gum inflammation that quietly build until the smell gives it away. The aim is to work out when you can start with simple home care, and when it’s time for a veterinary check because pain, infection, or a medical illness may be underneath.^{1, 2}

What causes bad breath (halitosis) in cats?

Bad breath is a symptom, not a diagnosis. The smell can be a useful clue, but the cause still needs checking—especially if it’s new, persistent, or getting worse.^{1, 3}

Dental and mouth causes (most common)

In most cats, halitosis starts in the mouth. A thin film of plaque forms on teeth, then mineralises into tartar (calculus). That rough surface holds more bacteria at the gumline, driving gingivitis and, if untreated, periodontal disease. The odour comes from bacterial by-products and inflamed tissue.^{2, 3, 4}

• Plaque/tartar build-up and periodontal disease (the everyday, creeping cause).^{2, 4}
• Gingivitis and stomatitis (inflamed gums and mouth tissues can smell sharp and unpleasant).^{4, 5}
• Broken teeth, tooth root infection, or oral abscess (often a strong, foul smell).⁵
• Something stuck in the mouth (string, bone fragments, food lodged under the gum).³
• Oral tumours or ulcers (less common, but important not to miss).³

Medical causes outside the mouth

Sometimes the breath changes because the body chemistry changes. Kidney disease and diabetes are classic examples, and both are more common as cats age.³

• Kidney disease can cause a chemical or ammonia-like smell and may be associated with mouth ulcers in more advanced cases.³
• Diabetes mellitus can cause a sweet or fruity smell (ketones), particularly if the diabetes is poorly controlled.³

Signs that often come with halitosis

Some cats keep eating while their mouth hurts, so it helps to watch for small, quiet changes. These signs commonly travel with dental disease and other oral problems.^{1, 2, 6}

• Yellow-brown tartar on teeth or red, swollen gums
• Drooling, especially if it’s new
• Pawing at the mouth or head-shy behaviour
• Chewing on one side, dropping food, or favouring softer food
• Reduced appetite, weight loss, or change in grooming

When to see a vet (and when it’s urgent)

A mild food smell after a meal is one thing. A persistent change in breath is different, and it’s worth booking a check-up—especially if your cat is older, has known dental disease, or you can see tartar or inflamed gums.^{1, 6}

Seek prompt veterinary care if bad breath comes with any of the following:

• Not eating, crying when chewing, or hiding more than usual
• Facial swelling, bleeding from the mouth, or obvious broken teeth
• Vomiting, marked thirst/urination changes, or sudden weight loss
• A sudden, strong “chemical” smell (especially in a senior cat)³

Diagnosis: what the vet may do

Most cats need more than a quick peek at the front teeth. A proper dental assessment may include looking under the gumline and taking dental X-rays—often under anaesthesia—because that’s where much of the disease hides.^{4, 7}

Depending on what’s found, your vet may also recommend blood and urine tests to check for medical causes such as kidney disease or diabetes, especially in middle-aged and older cats.³

Treatment options that actually work

Professional dental treatment

If periodontal disease is present, the most effective treatment is a professional dental clean performed under general anaesthesia, with cleaning below the gumline and polishing to slow plaque re-attachment. This is also when extractions can be done if teeth are painful or beyond saving.^{5, 7}

Be cautious with “anaesthesia-free” dental cleaning services. They may remove visible tartar, but they can’t safely clean below the gumline or properly assess the mouth, and they can give a false sense that the disease has been treated.^{7, 4}

Medication and medical treatment

If there’s an infection, inflammation, or an underlying illness contributing to the smell, treatment may include pain relief, targeted antibiotics (when appropriate), and management of the underlying condition. The key point is that medication alone usually won’t fix dental disease if tartar and infected pockets remain.^{5, 3}

Home dental care to prevent bad breath

Once the mouth is comfortable, daily home care slows the return of plaque. Brushing is the most reliable option, even if you only manage a small section of the outer tooth surfaces at first.^{1, 7}

Toothbrushing (practical approach)

• Use a cat toothbrush or soft finger brush, and toothpaste made for cats.^{1, 7}
• Start with a few seconds and build up. Many cats tolerate brushing better if you lift the lip and focus on the outer surfaces.
• If gums look inflamed or brushing seems painful, stop and get a vet check—brushing sore gums can worsen aversion and discomfort.⁸

Never use human toothpaste

Human toothpaste isn’t designed to be swallowed. In cats it can cause stomach upset, and some products contain ingredients that are unsafe for pets. Stick to feline toothpaste from your vet or a reputable pet supplier.^{1, 7}

Dental diets, treats, and other supports

If brushing isn’t possible, ask your vet about dental diets and other oral health products. They can help, but they work best as support rather than a replacement for brushing and professional care.^{8, 7}

Diet and cat breath: what to change (and what not to claim)

Food can change the smell of the breath, especially strongly flavoured diets, but it doesn’t remove dental disease on its own. Wet food isn’t automatically “better” for teeth than dry food; what matters is whether the diet is designed for dental health and how much plaque control your cat gets overall.⁸

If your cat has persistent halitosis, treat it as a health clue rather than a dietary nuisance: check the mouth, address dental disease early, and use diet as one part of prevention.

“Natural remedies”: what’s safe and what to avoid

Most “home cures” for bad breath in cats are either unproven or risky. Avoid adding essential oils (such as tea tree, peppermint, or spearmint) to your cat’s water or food—cats are more sensitive than people to many concentrated oils, and accidental overdosing is easy.

Safer, evidence-based options are simpler: veterinary dental care, toothbrushing with cat toothpaste, and vet-recommended dental products.^{1, 7, 8}

Final thoughts

Bad breath is often the first outward sign of a quiet problem at the gumline. When it’s caught early, treatment is usually straightforward: a proper veterinary exam, dental care if needed, then steady home maintenance. Left to drift, it tends to deepen—into pain, infection, and teeth that can’t be saved.^{2, 4, 7}

References

1. RSPCA Pet Insurance Australia – Guide to cat dental care
2. RSPCA NSW – Dental disease signs (including bad breath) in cats
3. PetMD – Bad breath in cats: causes, symptoms, and when to see a vet
4. Merck Veterinary Manual (Cat Owners) – Dental disorders of cats
5. VCA Animal Hospitals – Halitosis in cats
6. Cat Protection Society of NSW – Factsheet: Feline dental care
7. American Animal Hospital Association (AAHA) – Dog & cat dental disease: professional cleanings, anaesthesia, and home care
8. AAHA/AAFP – Feline life stage guidelines: feline dental care (including dental diets and anaesthesia-free dentistry)