Causes and Treatment of Rodent Ulcers in Cats

by beaconpet
Causes and Treatment of Rodent Ulcers in Cats

Rodent ulcers in cats are severe-looking sores that can appear on their lips, but despite their name, they actually have nothing to do with rodents. These ulcers are most often a result of an allergic reaction or irritation from ectoparasites like fleas. While they may look distressing, they are usually not painful for cats. However, they do require veterinary attention to ensure proper healing. In this article, let’s explore the causes and treatment options for rodent ulcers in cats, as well as how to prevent their recurrence with BEACONPET.

Causes and Treatment of Rodent Ulcers in Cats

Rodent ulcers are a common condition in cats that often appear on their lips, although they are not usually serious and have nothing to do with rodents. These ulcers typically occur as a result of an allergic reaction or irritation from ectoparasites such as fleas. While rodent ulcers may bleed, cats often do not show obvious signs of discomfort or pain. However, it is important to seek veterinary attention to help these ulcers heal properly.

Causes and Treatment of Rodent Ulcers in Cats

What Are Rodent Ulcers in Cats?

Rodent ulcers, also known as eosinophilic ulcers or indolent ulcers, are severe-looking lesions that develop on a cat’s lips, most commonly on the upper lip. These ulcers are one of three types of lesions that make up a syndrome called Eosinophilic Granuloma Complex (EGC). The other two types of lesions associated with EGC are eosinophilic plaques and eosinophilic granulomas. The name “rodent ulcer” originated from an old, incorrect belief that these lesions were caused by the bite of a mouse or rat. To avoid perpetuating this myth, the term “indolent ulcer” is becoming more widely accepted in the veterinary field.

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Rodent ulcers, although they may appear worse than they feel to the cat, present with definitive signs that make them easy to identify. The key symptoms of rodent ulcers include:

  • Sores with well-defined, raised edges and ulcerated depressions
  • Thickened tissue around the ulcers
  • Ulcers can appear on one lip or both, most commonly the upper lip
  • Cats may experience mild discomfort but are usually not in significant pain

Rodent ulcers often seem to appear suddenly and without warning, sometimes overnight. They are typically red, raised, and located on the lip. These ulcers’ sudden and rather gruesome appearance might lead cat owners to suspect traumatic injury. However, most cats show no signs of distress as the ulcer is localized and relatively painless.

Symptoms of Rodent Ulcers in Cats


While not caused by rodent bites, veterinary researchers have yet to identify one specific cause for rodent ulcers or the underlying Eosinophilic Granuloma Complex (EGC). Some studies suggest that heredity is a contributing factor, while others indicate that EGC lesions, including rodent ulcers, flare up due to a hypersensitive allergic response. Ulcers resulting from allergies are likely to recur until the allergen is removed. In rare cases, rodent ulcers may occur due to more serious underlying diseases that require further investigation. Various triggers have been identified for the development of rodent ulcers, including:

  • Food allergies
  • Hypersensitive reactions to ectoparasites such as fleas, ticks, or mosquitoes
  • Environmental allergies
  • Bacterial or fungal infections
  • Autoimmune disorders
  • Feline leukemia

Although there is no specific breed disposition for rodent ulcers, they tend to occur more frequently in female cats under six years of age.

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Since rodent ulcers have a distinct presentation, they are relatively easy to diagnose. A cat’s clinical symptoms and physical examination findings are usually sufficient for a veterinarian to identify the condition. However, if a more definitive diagnosis is needed or desired, the vet may take cytology samples. These samples can be obtained using clear tape or fine-needle aspiration. Fine-needle aspiration involves inserting a needle into the lesion to collect cells, which are then examined under a microscope.

Diagnosing Rodent Ulcers in Cats

How to Treat Rodent Ulcers

The acute treatment of rodent ulcers, regardless of their underlying cause, involves reducing inflammation and eliminating any bacterial or fungal infection that may be present. These ulcers will not heal on their own. A veterinarian may prescribe antibiotics or antifungal medication, as well as a short course of anti-inflammatory steroids. If other underlying diseases, such as feline leukemia or an autoimmune disorder, are contributing to the development of rodent ulcers, the veterinarian will discuss treatment options for those specific conditions as well.


The prognosis for cats with rodent ulcers depends on the underlying cause. If the ulcers are due to an allergy, hypersensitivity, or infection, removing the irritating factor will prevent recurrence and allow for a full recovery. However, if an underlying disease is responsible, the prognosis will vary based on the severity and treatment responsiveness of that condition.

The prognosis for cats with rodent ulcers depends on the underlying cause


Since hypersensitivity to ectoparasites is a common cause of rodent ulcers, using flea and tick medication can help prevent these ulcers (although the parasites can still bite the cat’s skin and cause a reaction). It is essential to administer this prevention on time and year-round to ensure continuous coverage.

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Some cats may also be allergic to certain animal proteins. If a cat has rodent ulcers, feeding them a commercially available limited-ingredient diet or a veterinary prescription diet can help reduce the severity and frequency of the ulcers.

Frequently Asked Questions

1. Are rodent ulcers in cats contagious?

No, rodent ulcers and other lesions associated with Eosinophilic Granuloma Complex cannot be passed to humans or other animals.

2. Are rodent ulcers in cats painful?

Fortunately, rodent ulcers do not appear to cause significant pain to cats and often look worse than they feel. However, it is important to contact a veterinarian if a cat is rubbing or pawing at the sores or seems uncomfortable.

In conclusion, rodent ulcers in cats are not caused by rodents but rather an allergic reaction or irritation from ectoparasites. While they may look severe, they are usually not serious and can be effectively treated with veterinary attention. Proper diagnosis, treatment, and prevention measures will ensure a cat’s full recovery and minimize the recurrence of these ulcers.

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