A swollen lip in cats can be particularly alarming, often leaving you wondering about the underlying cause. While there are several potential reasons for this condition, three main causes stand out: indolent ulcers, lip granulomas, and dental diseases. In this article, we'll discuss these three primary causes of swollen lips in cats, aiming to equip you with the knowledge to better understand and care for your feline friend.

1. Rodent ulcer or indolent ulcer

Rodent ulcers, also known as indolent ulcers, are one of the more common causes of swollen lips in cats. Despite its somewhat unusual name, this condition isn't caused by rodents. Instead, it's a type of eosinophilic granuloma complex, an immune-mediated condition that manifests in the skin and mucous membranes.

What does a rodent ulcer look like?

Indolent ulcers, commonly known as rodent ulcers, are a distinct type of lesion that can be concerning when you first notice them on your cat. These ulcers usually appear as reddish (erythematous) and somewhat hollowed-out (concave) sores, often with a crusty surface. They are most commonly located on the upper lip, near the area adjacent to the canine teeth.

As these ulcers progress, they may thicken and develop raised, defined borders and result in the appearance of puffy lips in your cat. You might notice their color changing to orange or tan. In some cases, the center of the ulcer might show signs of tissue death (necrosis), which can look like a deeper, more serious injury in the middle of the lesion.

It's important to be aware that your cat's natural behavior, like licking, can contribute to the development or worsening of these ulcers. This means that even though the ulcers themselves may not be painful, the constant licking can aggravate the condition. Additionally, similar lesions might also be found inside your cat's mouth, not just on the visible lip area.

rodent ulcer in cats
If you notice swollen lips in your cat, make sure to inspect the underside to look for a rodent ulcer

What causes rodent ulcers in cats?

The exact cause of rodent ulcers in cats is still not completely understood. However, it's believed to be related to an overactive immune response, possibly triggered by allergens, food sensitivities, or environmental irritants. Some cats may have a genetic predisposition to this condition.

Diagnosis and treatment

Diagnosing a rodent ulcer typically involves a thorough examination by a veterinarian. In some cases, a biopsy may be necessary to confirm the diagnosis and rule out other conditions like cancer or infections.

Treatment often involves managing any underlying allergies or sensitivities, as well as administering medications to control the immune response. This might include corticosteroids or other immunosuppressive drugs such as cyclosporine (Atopica®). In some cases, dietary changes may also be recommended, especially if food allergies are suspected.

While rodent ulcers can recur, with proper management, most cats can lead a comfortable, normal life. It's important to work closely with your veterinarian to develop a treatment plan tailored to your cat's specific needs.

2. Lip granuloma

Another significant cause of swollen lips in cats is lip granuloma, also a part of the eosinophilic granuloma complex.

Identifying a lip granuloma in cats

Lip granulomas in cats appear as firm, raised swellings on the lips, especially the bottom lip. They can sometimes be ulcerative and may look reddish or raw but often only appear as a large swelling on the bottom lips, at the midline.

lip granuloma in cats
A swollen lower lip at the midline is likely a lip granuloma

What triggers lip granulomas?

The exact cause of lip granulomas in cats is not fully understood, but they are believed to be a hypersensitive reaction, possibly to environmental allergens, food components, or even fleas. As with rodent ulcers, there may also be a genetic component to susceptibility.

Diagnosis and treatment

Diagnosing a lip granuloma involves a thorough dermatological examination. Since these granulomas can be associated with allergies, your veterinarian may also recommend allergy testing or dietary trials.

Treatment typically includes corticosteroids or other immunosuppressive medications to reduce the immune system response and inflammation. If allergies are identified as a trigger, specific interventions to manage these allergies will be necessary. This may involve changes in diet, flea control measures, anti-allergy medication, or modifying the cat's environment.

Management of lip granulomas can be ongoing, and regular follow-ups with your veterinarian are essential to adjust the treatment plan as needed and ensure your cat's comfort and health.

3. Dental disease or periodontal disease

When investigating swollen lips in cats, it's important not to overlook the role of severe dental and periodontal disease. This condition is not only common in cats but can also significantly impact their overall health, well-being, and quality of life.

The connection between dental health and swollen lips in cats

Periodontal disease in cats involves the inflammation and infection of the structures supporting the teeth, including the gums. As this condition progresses, it can lead to swelling of the gums and surrounding tissues, sometimes extending to the lip area.

Signs of dental disease in cats

Apart from swollen or puffy lips, signs of dental disease in cats include foul-smelling breath, difficulty eating, drooling, and visible tartar on the teeth. In many cases, however, there are no distinct symptoms revealed by affected cats with dental disease.

In advanced cases, there may be loose or missing teeth, bleeding gums, and noticeable pain or discomfort.

Why prompt treatment is essential

It's vital to address dental issues promptly, as they can lead to more severe health problems if left untreated, including potential infections that can spread to other parts of the body.

Also, despite what your cat may not reveal, severe dental disease is painful and uncomfortable, which can affect their overall behavior and quality of life.

Treatment and prevention

Treatment typically involves professional dental cleaning by your veterinarian and may require tooth extractions in severe cases. Your veterinarian may also prescribe antibiotics and pain relief medications.

Preventive care is equally important. Regular dental check-ups, and good oral hygiene practices, including brushing your cat's teeth, feeding dental kibble, or using dental treats and toys can help prevent the onset or progression of dental disease.

FAQs

Why is my cat's bottom lip swollen and looks like a bump?

The most common cause of a swollen bottom lip in a cat is a lip granuloma. A lip granuloma is most often a hypersensitivity response to an allergen. In some instances, it can be due to eating or drinking from plastic bowls or dishes.

Will my cat's swollen lip go away?

If the swollen lip is caused by a rodent ulcer or lip granuloma, it may go away if the offending allergy has been removed. Otherwise, you should see your veterinarian for a diagnosis and treatment plan.

Can I give my cat over-the-counter medication for swollen lips?

No, never give your cat any medication without consulting your veterinarian first. Some medications can be toxic to cats, and your veterinarian will need to determine the underlying cause of the swollen lip before prescribing any treatment.


In conclusion, swollen lips in cats can be symptomatic of conditions including rodent or indolent ulcers, lip granulomas, or severe dental diseases. By understanding these diseases, you can better monitor your feline friend and seek veterinary assistance when needed. Remember, these conditions are manageable with the right care and treatment. Regular check-ups with your veterinary team are helpful to prevent and control these conditions.