Lip Sores & Mouth Ulcers In Cats

For a variety of reasons, lip and mouth problems are common in both kittens and cats. Most are easy to fix, but beware: they are hard to tell apart and some are extremely serious. Here are the essential facts for cat owners.

Causes Of Lip & Mouth Sores

In order of frequency, oral lesions of cats are most often caused by:

  • Eosinophilic granuloma complex
  • Viral infection
  • Renal failure
  • Gingivitis & stomatitis
  • Squamous cell carcinoma
  • Chemical or physical injury

Now let’s look at each of these in detail.

Eosinophilic Granuloma Complex

EGC is the name for a variety of diseases all caused by an accumulation of a particular white blood cell called eosinophil (“Ee-Oh-Sin-Oh-Fil”). These are the cells normally associated with allergies and parasites, but in EGC they cause ulcers, erosions, swellings or plaques of the skin and mouth.

The picture at the start shows a typical lip margin ulcer caused by EGC. If this early lesion is untreated it will spread to both sides and cause permanent erosion of the lips. I’ve deliberately chosen a mild case so you can identify it in time.

cat swollen chin
swollen chin caused by EGC

The picture here is another version of EGC where the chin of a cat gets puffy and swollen. If you look closely you can see the swollen area of gum has a yellowish tinge from the eosinophils.

Treatment with corticosteroids is usually simple, cheap and effective. There’s a link in some cats with flea bite so you should also add a good cat flea preventative whether you’ve seen fleas or not.

If there isn’t a quick response, I always double check the diagnosis with a biopsy or blood test to rule out the other conditions below.

Viral Infection

cat flu look
Mouth ulcers, conjunctivitis and nasal discharge in a poor kitty with cat flu

Both cat flu viruses commonly cause tongue ulcers especially in kittens. Sometimes they also cause gum ulcers, and are even linked with stomatitis (see later). Nasty!

You can read all about cat flu here.

Renal Failure

Uraemic ulcers cat

These odd white ulcers on the gums are associated with the uraemic syndrome of advanced kidney disease. Look closely and you’ll see another ulcer on the edge of the tongue. These have occurred due to high blood levels of toxins that are normally excreted by the kidneys.

Sadly, uraemia is a late and very bad sign usually associated with a poor response to treatment. Where possible, making a diagnosis earlier using routine wellness testing gives much better outcomes.

Gingivitis & Stomatitis

Without good dental care, all cats eventually develop gingivitis. However, in some unlucky ones, mouth inflammation and infection appears more rapidly. Causes include viral infections such as cat flu and FIV, genetic faults, and poor early nutrition.

cat stomatitis extractions
Improvement after tooth removal

Gingivitis in affected cats often progresses to stomatitis, as the inflammation and ulceration spreads away from the tooth-gum margin. These cats may continue to eat, but are usually in severe pain. Signs of gingivitis-stomatitis include bad breath, reluctance to eat hard food, drooling, and pain on opening the mouth.

If you get to look inside, you’ll see a horror show of bleeding and ulcerated gums. While they improve with good dental hygiene, severe cases of stomatitis respond best to complete tooth removal. It’s a radical step but it’s all-too-often necessary to treat the ongoing pain.

Squamous Cell Carcinoma

Although cancers are thankfully less common, they have a bad habit of masquerading as other conditions. This is especially true for squamous cell carcinoma (SCC), which can look either like a lump or like a slowly spreading ulcer or sore.

SCC is well known for affecting the noses and ears of cats that sunbathe. However, it can also be found inside the mouth, sometimes hidden by dental disease. This is why a biopsy is necessary whenever a supposedly simple condition doesn’t respond like it should.

Early diagnosis can lead to curative surgery, as well as a lot less unnecessary treatment.

Chemical or Physical Injury

Animals that groom are uniquely sensitive to their environment. When a cat gets toxic chemicals on the coat or feet, their first response is to lick them off. The most severe cases of oral ulceration I have seen have been a result of exposure to household cleaning fluids.

To prevent this, never allow cats near areas being bleached or disinfected, and remove any chemical exposure straight away using dilute dishwashing liquid.

Physical injury, such as foreign material becoming lodged in the mouth, is rare enough that I can’t recall a case. However, I’m sure there are some cats who’ll give anything a red hot go, so it’s always worth getting your vet to take a close look.

In conclusion, if your cat has a mouth or lip sore, it’s probably one of the causes above. However, as much as I’ve tried to explain them, their appearances overlap too much to ever replace the opinion of an experienced vet. And with a diagnosis there’s a lot that can be done to help.

Have something to add? Comments are welcome below and will appear within 24 hours of lodging.
By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These help topics are from a series regularly posted on Facebook and Twitter. Subscribe via email here to never miss a story! The information provided here is not intended to be used as a substitute for going to the vet. If your pet is unwell, please seek veterinary attention.


One Reply to “Lip Sores & Mouth Ulcers In Cats”

  1. Thanks for the information on your site it has helped it looks like my cat might have an ulcer on the top side of her gum it looks very similar to the pictures. I will find out for sure today she is going to the vet for her mouth to be looked at.

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