Mouth Sores in Cats

Mouth sores in cats are painful ulcers, erosions, or inflamed areas that can affect the gums, tongue, lips, cheeks, palate, or back of the mouth. Some sores are small and hard to see. Others are dramatic, with bright red tissue, bleeding, drooling, bad breath, or obvious pain when your cat tries to eat or groom. While pet parents may notice a “sore,” vets usually think about the larger problem behind it, such as dental disease, stomatitis, viral infection, kidney disease, trauma, or a mass.

This symptom matters because cats often hide pain. A cat with significant oral disease may still approach food but then back away, chew on one side, drop kibble, paw at the mouth, or become withdrawn. In more severe cases, cats stop eating altogether, which can become dangerous quickly. Pain-related poor appetite can lead to dehydration, weight loss, and in some cats, secondary liver problems from not eating.

Mouth sores are especially common in cats with severe dental inflammation. Feline chronic gingivostomatitis is one of the best-known causes and can create intense inflammation in the gums and tissues at the back of the mouth. Viral disease, especially feline calicivirus, can also cause oral ulceration. Some cats develop ulcers from uremia related to kidney failure, while others may have lesions linked to allergies, caustic exposures, or oral tumors.

Because the list of causes is broad, home diagnosis is not reliable. The same red, ulcerated appearance can come from very different conditions. Your vet may need an oral exam, bloodwork, dental X-rays, infectious disease testing, or even a biopsy to sort out what is happening and which treatment options fit your cat and your budget.

The most common causes of mouth sores in cats are dental and inflammatory conditions. Gingivitis, periodontal disease, tooth root infection, tooth resorption, and feline chronic gingivostomatitis can all create painful ulcerated tissue. In stomatitis, the inflammation often extends beyond the gumline into the cheeks, tongue, palate, and tissues at the back of the mouth. These cats are often very painful, drool, have foul breath, and may resist having the mouth touched.

Infectious disease is another major category. Feline calicivirus is well known for causing oral ulcers, especially during upper respiratory infections. Cats may also have sneezing, nasal discharge, fever, or eye inflammation at the same time. Other viral infections, including feline leukemia virus and feline immunodeficiency virus, may contribute to oral inflammation or make severe mouth disease more likely in some cats.

Systemic illness can also show up in the mouth. Cats with advanced kidney disease may develop uremic ulcers. Toxin or chemical exposure, including contact with irritating plants or caustic substances, can damage oral tissues. Trauma from chewing sharp objects, burns, or electrical injury is less common but possible. Eosinophilic granuloma complex, often associated with allergy, can cause lip or oral lesions that may look ulcerative.

Oral masses are another concern, especially if the sore is one-sided, raised, bleeding easily, or not healing. Squamous cell carcinoma is an important oral cancer in cats and may first appear as an ulcerated lesion. That is one reason any persistent mouth sore, especially in an older cat, deserves prompt veterinary attention rather than watchful waiting at home.

See your vet immediately if your cat has mouth sores and is not eating, is having trouble swallowing, is drooling constantly, has blood in the saliva, or seems weak or dehydrated. The same is true if your cat is open-mouth breathing, has facial swelling, or may have chewed a toxic plant or caustic substance. Cats can decline fast when oral pain prevents normal eating and drinking.

Schedule a prompt visit within 24 hours if you notice bad breath with red gums, pawing at the mouth, dropping food, weight loss, hiding, or a sudden change in grooming. These signs often point to significant oral pain even when the sore itself is hard to see. Kittens and senior cats deserve extra caution because infectious disease, dehydration, and underlying illness can affect them more quickly.

A sore that lasts more than a few days, keeps returning, or appears as a lump, crater, or one-sided lesion should be checked soon. Persistent ulcers can be linked to stomatitis, tooth root disease, eosinophilic granuloma complex, kidney disease, or oral cancer. Waiting too long can mean more pain and fewer treatment choices.

If your cat is still eating and acting fairly normal, this may not be a middle-of-the-night emergency, but it is still not a symptom to ignore. Mouth sores are painful, and many causes worsen over time. Early care often means faster pain control and a clearer, more affordable plan.

Your vet will start with a history and physical exam, then focus on the mouth if your cat will allow it. They will ask about appetite, drooling, bad breath, weight loss, upper respiratory signs, toxin exposure, and whether the problem seems sudden or chronic. Some cats with oral pain cannot be examined fully while awake, so your vet may recommend sedation or anesthesia for a complete oral assessment.

A full diagnostic workup often includes bloodwork and urinalysis. These tests help look for kidney disease, dehydration, infection, inflammation, and other systemic problems that can contribute to oral ulcers. Depending on your cat’s history, your vet may also recommend testing for feline leukemia virus and feline immunodeficiency virus. If calicivirus or another respiratory infection is suspected, diagnosis may be based on exam findings and history, though additional testing is sometimes considered.

For many cats, dental imaging is a key step. Dental X-rays taken under anesthesia can reveal tooth root abscesses, tooth resorption, periodontal disease below the gumline, and other painful problems that are not visible during a quick awake exam. An anesthetized oral exam also lets your vet assess the exact location and severity of lesions and perform cleaning, extractions, or sampling if needed.

If a lesion looks unusual, one-sided, raised, or nonhealing, your vet may recommend a biopsy. This is especially important when cancer, eosinophilic granuloma complex, or a less common inflammatory disease is on the list. The goal is not only to confirm that sores are present, but to identify the underlying cause so treatment options can be matched to your cat’s needs.

Home care should support, not replace, veterinary treatment. If your cat has mouth sores, offer soft, easy-to-eat food and fresh water in a quiet area. Watch closely for how much your cat actually eats, not just whether they approach the bowl. Keep a daily log of appetite, drooling, grooming, energy level, and body weight if you can do so safely at home.

Do not use human mouth rinses, peroxide, topical numbing gels, or over-the-counter pain medicines unless your vet specifically tells you to. Many human products are unsafe for cats or can worsen oral irritation. If your vet prescribes medication, give it exactly as directed and ask whether it should be given with food. If your cat refuses medication because the mouth is too painful, call your vet rather than forcing the issue.

Dental home care may help some cats after the mouth is stabilized, but brushing an actively painful mouth can make things worse. Ask your vet when it is appropriate to start brushing, dental wipes, or other oral hygiene products. Professional dental care is still important because much of dental disease sits below the gumline where home care cannot reach.

Monitor for red flags during recovery: not eating for a day, worsening drooling, blood in saliva, facial swelling, foul odor, vomiting, lethargy, or a sore that looks larger or more raised. Those changes can mean the original plan is not enough, the diagnosis needs to be revisited, or a more serious condition such as severe stomatitis or oral cancer is present.