Why does my cat have bad breath?

Why a cat's bad breath is an important signal

A temporary smell after a meal is no cause for alarm. Persistent halitosis that does not go away for days is another story. In cats, diseases of the mouth often progress unnoticed: the cat keeps eating and only becomes less active, plays less often and avoids having its face touched.

I always pay attention to small behavioural details: the cat grooms less or stops looking after its coat properly, its grooming becomes cursory, drooling appears, the cat eats on one side or chooses only soft food. In this context the smell is not a cosmetic problem but a clinical symptom.

Plaque, gingivitis and periodontitis

Bacterial plaque is the main cause of plaque-induced gingivitis, and tartar holds plaque in place and makes the teeth harder to clean. Gingivitis is inflammation of the gums only, without marked loss of bony support. Periodontitis involves loss of periodontal attachment, the formation of pockets and a reduction in the bony support of the tooth.

Periodontal disease in cats is sometimes underestimated because the cat does not “show” pain. Yet inflamed gums, bleeding and the build-up of bacteria in pockets produce a persistent smell. Without proper diagnosis and treatment the disease can progress.

• Red, swollen gums next to the teeth
• Blood on toys or in the bowl
• Visible tartar on the premolars and canines

Tooth resorption (TR) — a typical cause in cats

Tooth resorption, or TR, is one of the most common dental conditions in cats. The tooth tissue is destroyed, often starting at the neck of the tooth next to the gum. From the outside it may look like a “worn-down” tooth, a red line at the neck or a darkening.

This condition used to be described by older terms, but the current clinical term is tooth resorption (TR). TR is painful: a cat may keep eating but chew on one side, suddenly pull its head back, drop food or chatter its jaw; it often avoids dry food. A smell from the mouth is a common accompanying symptom of TR.

Chronic gingivostomatitis (FCGS) — not the same as gingivitis

Feline chronic gingivostomatitis (FCGS) is a severe chronic inflammatory disease in which inflammation spreads beyond the gums to other areas of the lining of the mouth. Gingivitis is limited to the gums, whereas in FCGS the alveolar and cheek lining, the areas behind the dental arches and other parts of the mouth may be affected.

In FCGS the gums are bright red, swollen and painful; the cat may drool, refuse food or cry out while eating. The smell in FCGS is often sharp. Diagnosis and treatment need a comprehensive approach: an examination under anaesthesia, X-rays, assessment of every tooth, sometimes extraction of problem teeth followed by anti-inflammatory therapy.

Damaged teeth and root infections

A single tooth with a crack, fracture, pulp damage or root infection can also be a source of smell. A cat may avoid having its face touched, but does not always refuse food altogether.

Darkening of the crown can point to damage to or death of the pulp, and dental X-rays help find hidden changes around the root. Without X-rays such teeth are easy to miss.

Reduced grooming and other behavioural signs

When the mouth hurts, a cat grooms less or stops looking after its coat properly — especially around the face. The coat becomes dull, matts appear and the cat looks “untidy”. Owners sometimes put this down to laziness, although the cause is in the mouth.

Other signals: the cat flinches when you try to stroke its face; eats with its head tilted to one side; chooses wet food instead of dry; playfulness disappears. These changes often accompany the smell rather than replace it.

Can the smell be something other than the teeth?

In the great majority of cats I find the cause of halitosis in the mouth. However, an unusual smell can sometimes go with systemic disease — kidney failure, diabetes, metabolic disorders. This is not the typical scenario, but a clinical assessment should be made. How to tell such a smell apart is in the article on the smell of acetone, urine or fish from the mouth.

If the smell persists after proper dental treatment, I recommend an additional general examination. It is important to rule out dental disease first — rather than assuming a “stomach” cause without examining the mouth.

How I establish the cause and what to do next

At the consultation I assess what can be seen without anaesthesia, but I make the final diagnosis after a full examination under anaesthesia with dental X-rays. This allows me to find TR, FCGS, periodontal pockets and hidden root infections.

The treatment plan is always individual: oral cavity sanitation, extraction of affected teeth, periodontal treatment, anti-inflammatory therapy. Brushing at home with veterinary toothpaste is an important part of prevention, but it does not replace diagnosis once the smell is already persistent.

Frequently asked questions