Sometimes it’s not teeth – other causes of bad breath in pets.

Bad breath, or halitosis, is very common in dogs and cats; however, there are a wide range of possible causes. Some are simple to treat; others less  so – but bad breath is almost always symptoms of an underlying problem.

There is one, harmless cause of halitosis – eating something rotten or smelly (much more common in dogs than cats)! Some dogs love eating      faeces or rotting food; this may be habit, or greed – but in a small percentage of cases is due to a condition called pica. This is when the animal        will eat pretty much anything, whether or not it is actually food-like, and may be due to mineral or vitamin deficiencies or certain brain diseases. In  most cases, however, eating rotting or smelly things isn’t due to a disease condition (although it may well lead to a nasty episode of vomiting and  diarrhoea!).

Metabolic diseases can also cause bad breath – especially diabetes and kidney failure. These conditions are both associated with changes in urination and drinking, and often weight loss. If untreated, both are potentially fatal. In diabetes, the breath may smell sweet (because of the excess sugar in the bloodstream); sour (because of increased bacterial growth, as the bacteria feed on the sugar); or musty (as yeasts grow in the mouth). In kidney failure, the breath may smell metallic (due to a build-up of toxins and waste products that the kidneys aren’t filtering).

Diseases of the respiratory tract such as sinusitis, nasal infections, and nasal tumours may also lead to bad breath. This is caused by the production of pus (dead, dying and decomposing white blood cells, bacteria and blood) in the nose, which trickles down into the back of the throat.

Some diseases of the gastrointestinal system can also cause halitosis, particularly megaoesophagus (where the gullet becomes swollen and dilated so food pools in it) or persistent vomiting (e.g. due to a blockage of the bowel, gastritis, kidney or liver disease). Infections of the mouth or the lip folds (e.g. in spaniels) may also cause it.

However, by far the most common cause of bad breath in dogs and cats is dental disease. Unless we regularly brush their teeth, most (although not all) dogs and cats will develop tartar and plaque on their teeth. This material is a mixture of salts from the saliva and masses of bacteria, living off the food in the mouth. While this is on the ends of the teeth, it isn’t a major problem (although it may smell a little); however, once it reaches the gum line, it rapidly becomes dangerous. When these plaques of bacteria touch the gum, they cause inflammation and infection of the gum tissues (called gingivitis). If untreated, this will spread down into the sockets of the teeth (periodontal disease) and lead to damage to the ligaments of the teeth. In some cases, infection may even penetrate the bone causing a tooth root abscess (which may burst through into a sinus causing sinusitis) or even osteomyelitis (infection of the bone). Even simple gingivitis is a risk factor for heart disease and kidney failure as the bacteria can easily enter the bloodstream – in severe cases, they may even suffer from blood poisoning and septic shock. In addition, a dog with severe gingivitis or periodontal disease will be unwilling to eat, and may eventually starve to death. If untreated, gingivitis will almost inevitably progress (the speed is variable; the fact of progression is not). As you’ve found, in many cases by the time the problem is diagnosed, the affected teeth cannot be saved.

So how do we know what’s going on?

In bad breath cases, you really do need to find out what’s causing the problem! For that, you’ll need to get him seen by your vet. Kidney disease is easily detected on a blood test (elevated levels of urea and creatinine, two waste substances normally filtered by the kidneys); it can also be detected by certain tests on the urine (urine protein/creatinine ratio, or UPC; and specific gravity). Diabetes may be apparent on a single blood test (as a raised blood sugar level) – however, if the patient is very stressed (more of an issue in cats), you can get a false positive result. For a definitive diagnosis, it is often best to send away a blood sample for a fructosamine test (which will show the average blood sugar level over the last few weeks).

Respiratory disease is usually easy to recognise (snotty nose, sneezing, coughing, facial deformity in the case of some tumours or polyps), although actually working out what’s causing it often requires advanced imaging (X-rays and endoscopy). Similarly, it is very unusual for bad breath to be the only symptom of a dog or cat with a significant gastrointestinal problem – vomit or diarrhoea, or regurgitated food matter, is a more common finding. Lip fold dermatitis is easily recognised on examination, as when opened out, the lip folds are red, sore and often smell musty.

As I said above, dental disease is the most common cause. Often, a simple visual examination will reveal significant plaque and tartar; and gingivitis may be obvious just by looking at red or swollen gums. Occasionally, there is a tumour or other disorder of the gums, but again, this is usually clear to see. Your vet will be able to tell you what the chances are that dental problems are causing your pet’s bad breath.

So what can be done about it?

That, of course, depends what the underlying problem is… Diabetes cannot usually be cured (although some cats, if caught early enough, can go into full remission if treated appropriately and aggressively), but can be managed with appropriate, diet, insulin injections and good blood-sugar monitoring. The same applies to chronic kidney failure – this can be managed with appropriate diet, ad lib access to water, and sometimes medication (ACE inhibitors).

Respiratory and gastrointestinal disease does need diagnosis and treatment – if the underlying cause is treated, the halitosis will usually resolve at the same time.

If the dental disease is significant enough to cause bad breath, it does need treatment. It is important to remember, however, that old pets can, perfectly safely, undergo anaesthesia for a dental as long as there aren’t any underlying heath issues. Old age is not a risk factor for anaesthesia per se, it just means it’s more likely that they’ll have some medical problem that is! In older patients (cats and dogs) use of a fast, modern anaesthetic gas (e.g. sevofluorane), intravenous fluids and good, careful monitoring means that their risk isn’t that much greater than a young pet, assuming they are otherwise healthy (and if they aren’t, bad breath is the least of your worries).

Fortunately, however, in many cases the vet will be able to remove the worst of the tartar by hand without needing a full dental under anaesthesia. Often, the dental disease can also be controlled (not cured, but kept manageable) by regular and diligent tooth brushing and the use of appropriate mouth-washes.

David Harris BVSc MRCVS


38 thoughts on “Sometimes it’s not teeth – other causes of bad breath in pets.

      1. My 13 year old Bichon has the same problem. We’ve seen two veterinarians, body X-ray, blood work and no answers. They each did a visual of his mouth but no X-ray there (since February 2018 that is). One vet said he has congestive heart failure. Any thoughts? I’m desperate to help him but running out of money to keep going to the vet offices to no avail.

        1. I’m afraid that from a history like that, there’s no way we can tell what’s going on! It could be anything from an infection, to a tumour, to gut disease, to a hormonal condition – the signs are just too vague. I think the next step would be blood tests, if not carried out so far, but beyond that, it depends on the clinical examination and detailed history. Another option if the first opinion vets aren’t getting anywhere would be to talk to them about being referred to a specialist referral hospital – although expensive, they often have the specialist staff and facilities to get a diagnosis where the general practice vets aren’t able to.
          Good luck!

          1. I think he needs to be looked at by your vet; this could indicate kidney or liver disease, or a wide range of other serious problems.

  1. I have a foster cat. Phineas is special in many ways. He has fought to live. History…ringworm 3 months to clear up. Upper respitory infection for an extended period 4 months treated with antibiotics (2) spiked 105 fever..left with neuro damage. Stopped growing at 11wks old. Is 4lbs. Not all teeth came in. Hes literally a perpetual kitten. His breath is rank!!! Rotten. Teeth he has are clean and white! Smell is constant! You can smell it sitting next to him. If you pet the top bridge of nose he yawns/stretches mouth. Its odd. He also has hearing balance and visual issues along with what id call mild downes syndrome. I live in a small town and our vets kind of blow me off about smell. His prior extensive bloodwork always shows infection but nothing else. HELP US PLEASE!!!

    1. In such a complex case I’m reluctant to try and solve it over the internet! A bad smell from the mouth that isn’t due to the teeth could be coming from a nasal infection or a foreign body (e.g. a grass seed or blade) up the nose, or any of the systemic conditions described above. If the first opinion vets aren’t getting anywhere, it might be worth talking to them about getting referred to a specialist referral facility? While more expensive, they will have specialist staff and equipment that may allow them to get to the bottom of the problem.
      Good luck!

      1. Thank you. Like i said he is special. Our very small Humane Society has tried so hard. Unfortunately they only have so much $$. Weve had a rough year there. Specialist are so expensive. Thank you.

  2. 2 cats ages 1yr and 5yrs. oldest cat was fine until we brought baby cat home to live.except for she has always acted like she had earmites. nope. slowly they both acted like ears were bothering them scratching bodies now too no fleas or bugs seen. Then here came awful poopsmell from bottom and their breath. baby vomits stopped growing and they she’d alot. they have never been outside. But I’ve noticed some same symptoms with me. can it be a parasite infection? can hookworms get into their ears? all thru my home I find little black specks and L shapes black white yellowish. I get negative labs from my fecal tests for ova and?? can we have a couple different types worms at one time.thank you so very much blessyou much.

    1. We’re not permitted to comment on human health issues, so I would strongly advise you seek attention qualified healthcare professionals regarding your own symptoms.
      Regarding your cats, it is very likely that they may have multiple parasites at the same time. The little black specks you’re finding are probably flea droppings – you very rarely see live fleas except in the most severe infestations – and the white and yellowish shapes might be tapeworm segments or fly eggs, but it’s impossible to tell exactly what’s going on over the internet without an examination. As a result I would very strongly advise you to get your cats checked out by your veterinarian, especially the kitten who isn’t growing. This has clearly reached the point where home treatment is not working, and the cats need professional attention.
      Good luck!

  3. My dog had her teeth cleaned and a tooth removed about 4 months ago. They found an abscess and she was on antibiotics. Her breath smelled so much better but now it has started again. I checked her teeth and there isn’t plaque build up. She doesn’t chew her bones as often and she doesn’t like me to brush her teeth. I did recently purchase a premium doggy tooth brush that I can add toothpaste or peanut butter to for her to chew on but if this doesn’t help, any other suggestions?

    1. OK, it might be a gum pocket, or even another abscess starting; it’s also possible that there’s plaque or tartar building up on the very back teeth, or perhaps under the gum line, where we can’t usually see it. Unfortunately, it’s also possible that the original abscess has recurred. I’m afraid to say I think another visit to the vets might be in order.

  4. My 12 year old lab/collie will only eat if we put warm gravy on his food. We have tried numerous different types and makes of food and he still will only eat with gravy. His breath stinks, he sometimes looks like he is losing balance when walking and he has lost weight. We took him to the vet and he just gave him a vitamin Jag and that was it. Please any help will be appreciated. Going to take him to a different vet and see what they say.

    1. I definitely think it would be worth another opinion if there’s been no improvement since the initial treatment; either from the first vet or of course a second. Good luck!

  5. My 7 year old pit female bailey has a of coppery smell to her breath she hasn’t been throwing up or anything her diet is health and she’s very active I’m just really worried by it because she was a rescue and she had a real rough life before I got her she hasn’t eaten anything crazy I’m just curious do you think it’s just a dental thing? Her teeth look health I have had time or money to take her to a vet yet it’s just the smell that worries me any advice on what to look for with the teeth would be great

    1. A metallic smell might be bad teeth (e.g. plaque or tartar, or a tooth root infection), but it could also suggest some other underlying health problems, such as kidney issues. I’d suggest you get her checked out by your veterinarian to make sure there isn’t anything more serious going on.

  6. I just got an 11 week old polydactyl kitten 2 days ago. Her breath smells like something is rotting in her mouth. Her gums are pale. She is eating, drinking and going to the bathroom normally (compared to kittens I’ve owned in the past). She also seems to be having a dark brown crust form around her nose. I’m not sure if they’re related ?

    1. I think getting her checked out would be a good idea – it might be a nasal infection, which can cause bad breath, but whatever it is, it does need to be seen I think.

  7. My older shitzhu was diagnosed as having a collapsing trachea.. he has an awful cough. I just noticed, during the cough, there’s a metallic smell. Could there be another cause for the cough?

  8. Hello good evening please help. Our dog Yuri is a shi tzu has the same condition. His teeth and gums slowly becoming black and his breath really stinks like its rotten. He lost his appetite 3-4days ago. The same with our past cats and dog after they have vaccinated with the anti-rabies last month. Our pets are dying one by one. I just want to know if the anti rabies may cause this kind problem? Or is it related to the vaccine? Thank you for your answers.

    1. I’m not aware of any demonstrated link between rabies vaccines and dental disease, to be honest; I think it more likely there’s something else going on here. Dental disease can cause all the symptoms you’re describing, although it has to be very advanced and been going on untreated for a very long time before a cat or dog will stop eating. I think a checkup with your vet to assess your dogs’ dental health and try to determine if there is any underlying cause is essential now.

  9. I have the same problem with my nearly 13-year-old Minpin named Gracie. She has had a heart murmur all her life and was diagnosed by a cardiologist with congestive heart failure. Her teeth are so bad and I know she is in pain but they will not perform dental work on her due to the fact that she has CHF because I was told they cannot do anesthesia on her. What options do I have and are there any specialist vets out there that would take on my situation pro bono ? Please help

    1. Unfortunately, it’s very hard – and probably impossible in most cases – to do a proper dental check without some degree of sedation or anaesthesia. There are safer anaesthetic options out there, but not every practice has the equipment or the expertise. I wouldn’t recommend an “anaesthetic free dental” as it doesn’t really get to the bottom of any problems, and can be very stressful for the patient. Where are you? It may be that there are other users who know a referral hospital who’d be willing to help in your area?

  10. My 1 year old cocker spaniel has bad diarrhoea, he’s really not hisself, very sleepy and lethargic and I’ve noticed he has very smelly breath. Really worries as this is so out of character.

    1. My best bet would be that he’s eaten something nasty…
      Diarrhoea alone isn’t usually dangerous, but if he’s not himself, I’d advise a vet check to make sure he’s not getting dehydrated or developing some underlying problem.

      1. Thank you. That may sound about right as we have been away in the Forest of Dean for the weekend where he’s been off exploring. How would I know if he’s got a temperature?

        1. Unless you have a thermometer, it isn’t easy – the best bet is to watch his behaviour; if he’s acting like he’s cold despite being in a warm room, or vice versa, that suggests a fever.

  11. My 15 year old heeler/lab mix Gracie spent a weekend at the vet 2 months ago, found out she has kidney disease. They flushed her kidneys, got levels in normal range and with prescription food levels ate staying in normal range.. shes eating and drinking well and in good spirits but in the last few weeks her breath smells like a sewer, and shes had a snotty nose… I’m concerned, but after paying the $443 vet bill two months ago and buying the expensive prescription food, I am unable to take her back to the vet right now.. I wish I knew something to help it because it is a truly horrible odor and I want to snuggle my old lady but it’s hard to hold my breath… 😉

    1. It might be that the kidneys are getting worse, but it could also be bad teeth. Have you considered brushing her teeth? It might also be worth ringing your vet and having a chat – explaining the situation but asking if there’s anything you can do at home until you come in for your next check up.

  12. I have a 4 yr old female Havanese. She’s had the worst breath & body odor since she was a puppy. Her breath is very stale & her BODY smells the same only ….. muted? She’s fine in every other way. She plays, eats, drinks, sleeps normally & is just the sweetest dog. But when she gets up in my face…woah! The smell could knock out Goliath! I would think this is simply a dental issue if it were just her mouth, but her body smells the same. Any ideas??

    1. Dogs groom themselves by licking, so it’s not uncommon for dogs with dental disease to spread a “weaker” version of the smell across the rest of their coat… probably time for a vet check!

  13. What a blessing you are Dr Harris. I have a 5-6 yr old rescue who is reported to be Papillion and Chihuahua. I see nor experience Chihuahua, but do see Papillion prominently. She had a 14 day stay in jail (solitary) a few months ago where she received a rabies vaccination. There, she lost one and a half pounds, never ate and wasn’t observed drinking. Skin and bones upon return with constant anxiety shakes. She eats quality dry food, usually no treats. Initially very difficult to get her to eat upon return but with coaxing finally happened. Found “wild weenies” she receives after an eaten meal which has put on one half pound. Now weighs six pounds. She was horribly abused, I have a 4 and 6 yr boys and my mom whom I confiscated her from. To my knowledge she has never had dental care. I’ve not taken notice until a recent change in severity of her bad breath. Gums at and above gumline are bright Dark red, almost like neon drying blood. Significant tartar calcification on each tooth I can see. She’s going to our vet asap.
    My question is this, directly above gumline her gums are bright red, beyond that there are irregular black patches seemingly overtaking the red color. They remind me of the color of how chow-chows mouth and tongue can appear. My dog’s tongue is ‘normal’ pinkish. She does have good return on her gums and seemingly no gum sponginess. Are the black areas normal for her reported breeds? Are there any small dogs with black gums? I’ve never taken any notice of her mouth before, I have no clue regarding any color changes. My deep gratitude for your amazing work, thank you

    1. Black patches on the gums are quite common in a range of breeds, and aren’t necessarily a sign of dental disease. Crossbreeds often have different pigmentation compared to purebreds as a result of the masking of genetic recessives, so you would expect some differences. Discoloured patches that are changing shape or colour, however, may suggest a health issue. Hope that helps!

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