Bad breath in cats: what it can mean
Many people assume cat breath smells of fish and that is that. Not so: a healthy cat has mild breath. A strong, persistent smell is almost always a clue, and the kind of smell can point to where the problem lies.
What is normal and what is not
Right after eating, a cat's breath may smell of their food, especially wet food with fish. But that smell soon fades. Strong, unpleasant, constant breath that you notice when the cat yawns, meows close to you or grooms is not normal at any age. In the great majority of cases the source is the mouth, but in some it comes from elsewhere in the body, such as the kidneys or metabolism. That is why bad breath is not fixed with a treat that masks it: you need to know where it comes from.
Cause number one: the mouth
Periodontal disease, with tartar, inflamed gums and bacteria below the gumline, is the most common cause of bad breath in adult cats, and it affects most of them from three years old to some degree. The bacteria living in the pockets between tooth and gum produce sulphur compounds that smell awful. Other causes in the mouth are tooth resorption, chronic gingivostomatitis, which produces very foul breath with drooling and pain, broken teeth or teeth with infected roots, calicivirus ulcers and food debris that builds up in flat-faced cats, whose teeth are crowded.
Look under the tongue
A very feline cause of sudden bad breath is a foreign body in the mouth: a thread or elastic band wrapped around the base of the tongue, a piece of bone or a splinter wedged between the teeth or in the palate. After a few days, the area becomes infected and smells very bad. The cat may drool, move their mouth oddly, paw at it or stop eating. If you can, very carefully lift the tongue from underneath: if you see a thread, do not pull it, as it may have been swallowed and be attached to the intestine. Take them to the vet.
When it smells of ammonia or urine
Breath smelling of ammonia, urine or metal, especially in an older cat, may be due to advanced kidney disease: the kidney does not clear toxins properly, they build up in the blood and are partly excreted in saliva, and mouth ulcers may also appear. It usually comes with increased thirst, lots of urine, weight loss, vomiting and poor appetite. It is a reason for a vet visit and blood tests soon. If the cat is very flat, vomiting a lot or not eating, the same day.
When it smells sweet, of acetone or overripe fruit
Breath that smells sweet, of acetone or overripe apples in a cat that is also drinking and urinating a lot, has lost weight, is vomiting, not eating or very flat may indicate diabetic ketoacidosis: uncontrolled diabetes makes the body burn fat unchecked and produce ketone bodies. It is an emergency. Go to the vet the same day, and if the cat is already a diagnosed diabetic, tell them they may be in ketoacidosis. Newly discovered diabetes can also show up like this, with no prior warning.
When it smells rotten and there is blood or a lump
In older cats, very foul breath with bloody drooling, a lump on the gum, the jaw or under the tongue, teeth that are loose for no reason, swelling on one side of the face or difficulty eating may be due to an oral tumour. The most common in cats is squamous cell carcinoma, which is aggressive and often diagnosed late because at first it is mistaken for a dental problem. Any lump or sore in the mouth that does not heal within one or two weeks must be seen by the vet, who will take a biopsy. Catching it early is what gives treatment options.
What the vet will do
First, an examination of the mouth with the cat awake, which gives a lot of information, although sedation is sometimes needed to see the whole mouth properly. The vet will assess tartar, gums, teeth, tongue, palate and the lymph nodes in the neck. If they suspect the cause is outside the mouth, or in a cat over seven or eight, they will request blood tests with kidney function and glucose. If there is dental disease, they will propose a clean under anaesthetic with dental X-rays. If there is a lump, a biopsy. As a guide in Spain: consultation 40 to 60 €; blood tests 80 to 160 €; full dental clean 180 to 400 € without extractions; oral biopsy 150 to 400 €.
What does not work
"Breath" treats and sprays that only mask the smell do not treat the cause and can delay diagnosis. Human mouthwashes and toothpastes are not suitable: they contain fluoride, alcohol or xylitol, which should not be swallowed. Home remedies such as coconut oil or bicarbonate of soda have no evidence and can irritate. Giving antibiotics without a diagnosis may reduce the smell for a few days, but the problem returns as soon as the course ends, and it encourages resistance. Bad breath of dental origin is only truly resolved with a full clean and then prevention.
Prevention
Tooth brushing with animal toothpaste, daily or at least several times a week, starting gradually. Dental diets or treats with Veterinary Oral Health Council certification as an extra. A mouth check at every vet visit and regular blood tests from age seven, which catch kidney disease and diabetes in time. And tidy away threads, elastic bands and ribbons: they are dangerous for the mouth and the gut. If your cat is flat-faced, keep a particularly close eye on the mouth, because their crowded teeth build up plaque more easily.
Persistent bad breath is not normal in a cat. It is almost always the mouth, but an ammonia smell points to the kidneys, an acetone smell to uncontrolled diabetes, which is an emergency, and a very foul smell with blood or a lump in an older cat to a possible tumour. Look under the tongue and book a check-up.
Educational content from Michipedia, translated from the Spanish original. It does not replace the advice of a vet or a feline behaviour specialist. Every cat is an individual.