Get

In Your Inbox

Catster is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Cat Mouth Sore: Causes, Signs & Treatments (Vet Answer)

Veterinarian examining cat's teeth and mouth

Have you noticed your cat has a mouth sore that seems to be lasting longer than your average cut or graze? Your cat may be suffering from something called Eosinophilic Granuloma Complex. It is not common knowledge, but cats are prone to mouth sores caused by this disease, and it can manifest in many different ways in cats.

They often present as sores that look like little ulcers around your cat’s mouth. They can also be found on other parts of the body such as the paws, legs, stomach, and groin area. There are granulomas, indolent ulcers, and plaques, and with each type, there are slightly different clinical signs witnessed. They are all similar in the way they seem to spontaneously develop and the fact that they all seem to respond positively to steroid treatment.

The severity can vary greatly. Some will resolve on their own and require no treatment while others will need intensive management. Read on below to find out more.

divider 3 paws

What Are Mouth Sores in Cats?

Eosinophilic granuloma complex in cats is a group of idiopathic conditions that are currently quite poorly understood. The exact cause of the disease is unknown, however, there are various suggestions involving parasites, allergies, and genetic factors.

The three main clinical presentations of eosinophilic granuloma complex include:

  • The ulcerative form (also known as indolent ulcer) is the type that is usually seen as a sore on your cat’s mouth. It is typically seen on the upper lip. They are normally red in color and do not appear to cause your cat any pain or irritation.
  • The plaque form is often found on the undercarriage of your cat, on the stomach, and on the inside of the hindlegs. This type of lesion is often itchy and red and can easily become infected, which complicates matters.
  • The eosinophilic granuloma is usually present as raised pink or yellow nodules. They can be located anywhere on your cat.
vet checking cat's mouth
Image Credit: mojahata, Shutterstock

What Are the Signs of Mouth Sores in Cats?

In cats, the most common sign of an eosinophilic granuloma is a raised, discolored ulcerated lesion near the mouth, although they can be found in other areas of the body as well. They are frequently found on the upper lip.

They can be small, red in color, raised masses, or large destructive lesions that cause the outline of the lips to be distorted. Some lesions can be infected or bleed. They can span the lips and develop in the oral cavity too.

Typical clinical signs seen usually include:

  • Mouth ulcers
  • Lesions on the upper lip
  • Ulcers on gums or elsewhere in the oral cavity
  • Raised lesions
  • Generally does not bleed
  • Painless
  • Potential to transform into a malignant tumor (this is a rare occurrence)

Diagnosis of Mouth Sores in Cats

To diagnose this disease, your vet will start by taking a full history from you and performing a physical exam on your cat. There will be certain clinical signs that will make them suspicious of the eosinophilic granuloma complex.

If they do suspect the disease, they will perform a fine needle aspiration biopsy (FNAB). This allows your vet to take a sample of a small number of cells to analyze under a microscope. They will be able to tell what type of cells are present in the mouth lesion and confirm if an eosinophilic granuloma is present. They will be looking for cells called eosinophils. The fine needle aspiration biopsy test can be done while your cat is conscious if they will tolerate it.

As only a very small sample of cells can be extracted, sometimes the test is inconclusive. If this is the case, a larger biopsy can be taken but this requires your cat to be put under general anesthesia.

Another way that your vet can sample the lesion is to do a sellotape impression smear. When looking at the imprint on the tape under a microscope, your vet can identify eosinophil cells present.

Biopsies can be useful to rule out more serious causes of sores such as malignant cancers. This can give owners peace of mind and help guide suitable treatment options. If an allergy is suspected as an underlying cause, your vet will carry out a workup to identify the allergen.

veterinarian checking the mouth of cat
Image Credit: PRESSLAB, Shutterstock

What Are the Causes of Mouth Sores in Cats?

Common causes of eosinophilic granuloma complex include:

  • Food allergies
  • Environmental allergies
  • Fleas
  • Other insects
  • Genetic predisposition

There is thought to be a genetic component to the diseases as there are reports of related cats all being affected. More research is required to understand exactly what is going on.

Common causes of the lesions are thought to be the presence of flea infestations, infectious pathogens, and dietary or environmental allergies. In some cats, the cause cannot be identified.

How Do I Care for a Cat with Mouth Sores?

Wherever possible, your vet will treat the underlying cause. If the underlying cause is not identified, steroids or cyclosporine are often used. If there is an allergy suspected, cats will often respond well to an elimination diet or dietary trial. If there is a flea infestation, your vet will prescribe flea treatment. It is important to keep up to date with flea treatment as the development of the lesion is thought to be triggered by a hypersensitivity reaction to fleas. Often flea bites can cause an overreaction from the cat’s immune system, which can make existing clinical signs worse.

Topical creams containing steroids can sometimes be used, however, a lot of these are not appropriate for use in the oral cavity so cannot be used around the lip and mouth area.

When clinical signs are severe, the cat may require antibiotic treatment. Steroids are frequently used in conjunction with antibiotics.

In rare cases, if clinical signs are severe and lesions are recurring frequently, then more aggressive management is required. In these cases, a referral to a veterinary dermatologist is recommended.

Veterinarian checks teeth to a big maine coon cat at vet clinic
Image Credit: Ermolaev Alexander, Shutterstock

divider cat faces oct 2024

Frequently Asked Questions (FAQ)

What is the prognosis?

The prognosis is usually good. Most cases respond very well to treatment. Some require long courses of antibiotics and steroids depending on the severity of clinical signs and if the lesion becomes infected. Depending on what the underlying cause is, some cats are likely to have recurring incidences.

If owners are aware their cat suffers from the disease, it is recommended that they monitor for signs very closely. This is to ensure treatment is given as soon as clinical signs appear. Some cats will need lifelong treatment whenever lesions are present if they keep recurring. 

Can mouth sores be cured?

There is no permanent cure for eosinophilic granulomas but there are plenty of effective management strategies. These can reduce and control clinical signs and offer cats comfort and relief, improving their quality of life.

How can I prevent mouth sores in my cat?

There is no way to prevent the development of eosinophilic granuloma complex. There are, however, ways that owners can minimize the risk factors. For example, using prescription flea medication, feeding a complete, well-balanced diet, and managing allergies can help to reduce the chances of lesions developing. It is also recommended to keep up to date with regular vet checks to ensure your cat is in good health.

Tabby-cat-meows-with-its-mouth-open
Image Credit: Kaan Yetkin Toprak, Shutterstock

divider cat faces oct 2024

Conclusion

Eosinophilic granuloma complex is a relatively common problem seen in cats. There are three different types described that affect cats in slightly different ways. It is believed to be an inflammatory response to certain things the cat is exposed to such as allergens, and insect bites, but there may also be a genetic component.

It is a poorly understood condition currently and more research is required to understand the ins and outs of the disease. Definitive diagnosis is carried out by biopsy. Treatment options usually include steroids and immunosuppressive drugs. The prognosis for most cases is generally good, but it can be a lifelong issue for some cats and they may require long-term management.

If you are concerned your cat may be suffering from eosinophilic granuloma complex, arrange an appointment for your vet to examine them.


Featured Image Credit: De Jongh Photography, Shutterstock

Want content like this delivered to you?

Sign Up For Our Newsletter

News, insights, expert advice, and everything cat

* By submitting, you agree to our Terms & Conditions and Privacy & Cookies Policy.


How useful was this post?

Click on a star to rate (you can leave written feedback after clicking submit)

Help us improve Catster for pet parents!

Your feedback really matters.

What did you like about this post? Also how can we improve it?

Join the conversation

Leave a Reply

You’re very welcome to leave a comment or question. Please know that all comments must meet our community guidelines, and your email address will NOT be published. Let’s have a positive and constructive conversation.


Talk With A Vet Online

Peace of mind,
anywhere, anytime

Affordable vet advice

12 Free DIY Cat Harnesses You Can Make Today (With Pictures)

If you intend to walk your cat outdoors, whether in your own yard, to the park, or around the local streets, you will...

Does Palmolive Kill Fleas on Cats? Vet Reviewed Effectiveness & Safety Explored

Fleas are the bane of every pet owner’s existence. They’re not only a nuisance for you, but they can cause itching and discomfort...

When to Euthanize a Cat With Seizures: The Difficult Decision & Vet Approved Advice

Seizures in cats can cause a great deal of distress, both to the cat and their human caretakers. Making the decision to euthanize...

How Many Cats Can You Legally Own in Pennsylvania? 2026 Update

Multi-pet homes are not uncommon in the United States, but some states have restrictive laws limiting the type and number of domestic animals...

More related

Is My Cat Drinking Enough Water? Vet-Approved Facts & Tips

Ensuring your cat is hydrated is incredibly important for its overall well-being. Cats need to intake around 1–2 milliliters of water per kilogram...

Cats and Snow: A Study in Feline Enrichment

Hi, I’m Dr. Lauren! Read my introduction to learn more about me and my two adventurous cats, Pancake and Tiller. One of my...

Why Is My Cat Drooling All of a Sudden? 13 Vet-Reviewed Reasons

Our feline friends can sometimes do odd things, so you may not always know what’s normal cat behavior and what isn’t. One feline...

10 Types of Birman Cats: Colors, Variations & Patterns (With Info & Pictures)

What is a Birman? According to Buddhist stories, the Birman cat was created by a Burmese goddess. The tale tells of a litter...

Keep reading

Why Does My Cat Bite My Ear? 10 Vet-Verified Reasons

Cats have long intrigued us with strange behaviors. One of the more unusual and often perplexing behaviors that some cats exhibit is the act of biting their owner’s ears. While cats are known for their enigmatic nature and instinctive habits,...

cat on woman's shoulder by head bite hair

How Do Cats Fall Asleep So Fast? Vet-Reviewed Feline Sleep Cycle

So, we’ve probably all used the term “catnap” to describe a short stretch of sleep that we take during the day. Perhaps it’s because cats are perceived as lazy, but anyone who lives with a cat knows that this is...

cute ginger kitty

Can Loud Music Harm a Cat? Vet-Reviewed Info

Ears, unfortunately, don’t have the handy ability to shut. If you enjoy listening to loud music, you’re forcing your cats to endure it, too. If you share your house with a cat, you might already be aware that loud noises...

cat lying between speakers

10 Best Cat Foods for Hairballs in 2026 – Reviews & Top Picks

You may have heard a bizarre hacking cough that floats through the house in the middle of the night and is typically followed by a nasty surprise in the morning. The hairball clean-up is never pleasant, regardless of the time...

grey-british-cat-sitting-near-food-bowl

Is Scented Litter Safe for Cats? Vet-Reviewed Facts & FAQ

Several online sources suggest that scented litter is bad for cats. It’s alleged to cause recurrent urinary tract infections (UTIs) due to irritation caused by fragrances added to mask the smell of cat pee. Others argue that scented litter should...

Catster_Is Scented Litter Safe for Cats

How to Protect Your Cat From Coyotes: 5 Vet-Reviewed Methods

Coyotes, also called prairie wolves, are great hunters. They live in packs and often hunt in pairs. They can be found all around the United States, including both rural environments and sometimes cities. Because these animals are opportunistic and can...

Coyote in the woods

Is Cinnamon Bad for Cats? Vet-Reviewed Safety Facts

Cats are obligate carnivores that have very different diets and nutritional needs than humans. However, there are a variety of foods that both cats and humans can eat. So can cats have cinnamon? Is Cinnamon bad for cats? In general,...

Can Cats Eat Chicken? Vet Approved Facts & FAQ

Your cat probably loves chicken. Most cats usually do. It is found in a lot of cat food, both canned and dry, and in cat treats, but perhaps you’re wondering if it’s okay for you to slip your cat some...

Can Cats Eat Chicken