There are a number of causes of bad breath, or halitosis, in cats. Some are harmless, for example bad breath may come from the breakdown of dietary protein in the gastrointestinal tract. A change in diet may result in an improvement in the smell of their breath. However, most cases of halitosis can be linked to disorders in the oral cavity.
Diseases in the mouth
The most common cause of bad breath, by far, is dental disease. Diseases of the gums and teeth can occur in cats from young adulthood. Bacteria attach to the teeth, forming a plaque which then hardens into tartar. Apart from the smell emanating from their mouth, there are some changes in your cat’s behaviour that you may notice if their teeth and gums are painful. Look out for increased salivation or a reluctance to eat. They often lose their enthusiasm for dry food, in particular, because it hurts their sensitive gums when they chew it. Fortunately, cats respond well to having their teeth cleaned and polished under general anaesthesia, and it won’t be long before their breath is smelling normal again.
Stomatitis is a poorly understood condition and is extremely painful for affected cats. Maine Coon, and oriental breeds, appear to be more susceptible. It’s thought to be associated with an immune reaction to the teeth, or to plaque on the teeth, possibly associated with a viral infection, or even stress, or genetics. The result is inflammation of the mouth, particularly behind the back molars. Apart from bad breath, these cats have a poor appetite and often drool. They also don’t groom themselves, so their coat may look untidy. Treatment can involve anti-inflammatory medications and regular teeth cleaning, but many individuals only get relief when their teeth are extracted. It can be quite a difficult condition to manage.
Oral tumours are relatively common in cats; they’re the fourth most common malignancy in this species, with squamous cell carcinoma and fibrosarcoma being the most likely tumour types. Cats with any form of mouth cancer often have trouble eating, and there may be an obvious swelling in their mouth. Their saliva may also be blood stained (1). Treatment can include surgical removal of the tumour mass, followed by radiation or, less commonly, chemotherapy.
Diseases of the body
While most cats with smelly breath have some disorder or abnormality in their mouth, some suffer from conditions affecting other parts of their body. This means that if your feline friend’s breath smells offensive, you mustn’t ignore it. Halitosis is an indication that it’s time for them to be examined by your veterinarian.
Respiratory infections can affect cats of any age and result in bad breath because the viruses involved can cause ulcers on the tongue and in the mouth. These ulcers may become secondarily infected with bacteria and this can smell offensive. Symptoms of these respiratory infections may also include: a runny nose and eyes, sneezing, fever and loss of appetite. Treatment is symptomatic, but could include: nebulisation, antibiotics if there is secondary infection and always lots of tender loving care, including soft foods and gentle grooming to make them feel good.
Kidney disease is another cause of halitosis in cats. The build-up of waste products, including urea in the blood, results in ulcers in the mouth and stomach and a distinctive odour to their breath. Kidney disease is most common in older cats; apart from bad breath, they may also drink lots of water, urinate more than normal, vomit regularly and lose weight. A key part of the ongoing treatment of kidney disease is dietary management, but affected cats may need fluid therapy and medication to control their blood pressure and electrolytes (2).
Cats with diabetes mellitus have problems with glucose metabolism and if their body becomes stressed by another illness, their diabetes worsens. This can lead to a condition known as diabetic ketoacidosis, where their body produces ketones in their blood and urine. These ketones can be detected on their breath; they often smell like acetone. Cats with diabetic ketoacidosis are listless, nauseous and clearly unwell. This condition can be life-threatening, so don’t hesitate to call your vet if you notice changes to the smell of your diabetic cat’s breath. They’ll need intravenous fluid therapy, insulin injections and regular blood tests to check their glucose and electrolyte levels, to make sure they’re returning to normal.
Working out the cause of your cat’s halitosis is usually straightforward if there is obvious tartar on their teeth and/or reddening of their gums. For those more difficult-to-diagnose diseases, a visit to the vet and blood tests are appropriate. The sooner your cat is examined, the earlier their condition is diagnosed and treated, and the quicker they can return to full health — and you can return to cuddling up with them, nice and close, with their much more pleasant breath.
1 Dhaliwal, R., Kitchell, B. and Maretta, S. (1998). Oral Tumors in Dogs and Cats. Part I. Diagnosis and Clinical Signs. Compend Contin Educ Vet., 20(9), pp.1011-1021. 2 Markovich, J., Freeman, L., Labato, M. and Heinze, C. (2014). Survey of dietary and medication practices of owners of cats with chronic kidney disease. Journal of Feline Medicine and Surgery, 17(12), pp.979-983.
Author info: Dr Audrey Harvey is a graduate of the University of Queensland, Australia, and has worked in small animal practices for 25 years. She is particularly interested in obesity management and the role of exercise in resolving behaviour problems in dogs.