Eosinophilic Granuloma Complex In Cats

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  • What is eosinophilic granuloma complex?

    Eosinophilic granuloma complex (EGC) is a condition characterised by the presence of skin lesions over various parts of your cat’s body.

    An eosinophil is a type of white blood cell that participates in allergic reactions and helps to fight certain parasitic infections. A granuloma is an inflammatory lesion that contains granulocytes. These are a type of white blood cell made up of small cytotoxic granules, which are released (degranulation) in response to a microorganism or parasite.

    The eosinophil’s job is to attack parasites. Once at the target location, it will release its granules to destroy the parasite. Cats with eosinophilic granuloma complex suffer damage to local tissues due to biochemicals released by eosinophils that are triggered during an allergic response.


    It is thought to be due to a reaction to certain allergens such as flea bites, food storage mite in dry food (T. putrescentiae), inhalant (atopy) allergy such as dust mites and pollen, and food allergies.


    Some cats may only experience a single episode, while others may have multiple outbreaks. There are three different types of lesion:

    • Indolent ulcer (eosinophilic ulcer or rodent ulcer): This affects cats of all breeds and ages, although it occurs three times as often in females as it is in males. Lesions typically develop on the upper lip, but can also develop on the tongue. They appear as a raised, thickened red/brown ulcer which is well defined and glistening. Generally, while they may look so, they are not painful to the cat.
    • Eosinophilic plaque: The lesion can appear on any part of the body, but most often develops on the abdomen or thighs. They appear as red, well-defined, raised, hairless lesions which may be ulcerated.
    • Eosinophilic granuloma (linear granuloma or collagenolytic granuloma): This is more common in males than females, and cats under two years old. The back legs are the most common location. Lesions appear as long, straight, thin lines that are raised and inflamed, and pink in colour. Distribution on the face is seen as swellings and nodules on the bottom lip and the cat has a “fat chinned” pout. Footpads may also be affected by eosinophilic granuloma.


    Your veterinarian will perform a physical examination of your cat, paying careful attention to the lesions. He will obtain a medical history from you including how long lesions have been present, other symptoms you may have noticed and any known allergies, are the symptoms seasonal, does the cat go outdoors?
    A tentative diagnosis may be made by visual examination of the ulcers. Your veterinarian may also decide to take biopsies of lesions for examination under a microscope.
    Diagnostic tests to rule out other possible causes such as fungal cultures to rule out ringworm and bacterial cultures to check for skin infections will be necessary.
    Skin prick test: A skin prick test is a test where multiple common allergens are pricked onto your cat’s skin, which is then evaluated 1-2 days later, if any of the pricks are raised and reddened, it can be indicative of an allergy to one (or more) of the allergens he was exposed to during the test.
    Food elimination trial: If your veterinarian suspects your cat has a food allergy, he will recommend a food trial. The cat is fed a novel protein, such as lamb, duck or kangaroo. During the trial, the cat must not receive any other food. If symptoms resolve, the cat will resume his normal diet to see if symptoms return.


    If it is at all possible, identify the underlying cause and treat it accordingly. This may include:

    • Ensure the cat is parasite free, treat regularly for fleas and worms.
    • Avoid and or eliminate suspected allergens.
    • Flea control for cats with flea bite hypersensitivity includes treating both the cat and the home.
    • Hypoallergenic diet for cats with food allergies.
    • Avoidance of the allergen for cats with inhalant allergy although this is difficult with dust mites and pollen. Avoid the use of scented products in and around the home, don’t smoke inside.

    In addition to addressing the underlying causes outlined above, treatment of the lesions may include:

    • Steroids: To reduce inflammation.
    • Immunosuppressive drugs: In severe cases, your veterinarian may prescribe immunosuppressive drugs such as Interferon.
    • Zyrtec (cetirizine): A common over the counter antihistamine that has anti-eosinophilic effects and can help in the treatment of eosinophilic granuloma complex.
    • Surgical excision or antibiotics: For unresponsive lesions.

    Image courtesy of Rocky Mountain Feline Rescue


    • Julia Wilson, 'Cat World' Founder

      Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio