Eosinophilic Granuloma Complex



Eosinophilic granuloma complex includes three distinct skin diseases in cats. All are thought to be either a result of allergies or reactions to parasite infestations and all respond to similar treatment.

The name of the disorder comes from the observation that in all cases, microscopic examination of the affected tissues reveals large numbers of eosinophils, a type of white blood cell that is involved in allergic reactions. In cats, allergies often produce skin itchiness and skin lesions as the predominant symptom. In cats with any of the eosinophilic granuloma complex diseases, the underlying trigger may be allergies to fleas or other parasites, to food ingredients, or to environmental substances such as pollens or house dust mites. Studies have shown that, at least in some cases, the tendency to develop eosinophilic skin diseases is inherited genetically. This observation means that both genetic predisposition, an environmental trigger, seem to combine to play a role in causing eosinophilic skin diseases. The fact that these disorders are rarely caused by a single trigger helps explain why eosinophilic granuloma diseases may flare up despite treatment, and may persist for months or years.

At least three specific types of skin lesions make up the eosinophilic granuloma complex:

  • Eosinophilic plaques are hairless, flat, raised areas on the skin that are often red, moist, and glistening. Plaques are most often found in the groin or axilla (armpit) or on the inside of the thigh. The condition seems to be very itchy, and cats often will lick the areas constantly.
  • Eosinophilic granulomas are hairless, raised, yellow areas of skin or of the mouth; they often have sores on the surface. The most common site is along the back of the thigh, although other areas of the body can be affected. Eosinophilic granulomas can occur inside the mouth and on the tongue. Cats with mouth involvement may drool and be unable to eat.
  • Indolent ulcer, or rodent ulcer, affects the upper lip. The lip becomes swollen, and a sore develops where the skin meets the mucous membrane of the inner lip.


Skin problems caused by the eosinophilic granuloma complex tend to wax and wane. If the underlying allergic cause can be determined and controlled, the problem can be prevented from reoccurring. Therefore, one aspect of dealing with eosinophilic granuloma complex should be to discuss with your veterinarian how to control some of the more common culprit allergens, such as initiating a diet that contains ingredients with a low likelihood of triggering an allergic response.

In some cats, the problem is seasonal. If fleas are present, a rigorous flea control program should be started. Seasonal problems may be due to bites of insects, such as mosquitoes, or to environmental substances that trigger allergic skin responses, such as pollens. Environmental allergies are identified by intradermal skin testing. Consulting a veterinary dermatologist may help in determining and eliminating underlying causes.


All three forms of eosinophilic granuloma complex respond to treatment with corticosteroids (cortisone-like drugs). Administration may be either by mouth (pills/tablets) or by long-lasting injection. Long-lasting injections are much more convenient but they carry a greater risk of causing adverse effects, including diabetes and unmasking (emergence of symptoms) of heart disease. Therefore, these sustained-release injections should be used in moderation, if at all, and only once an effort has been made to find the underlying cause of the allergic reaction and to eliminate it. If corticosteroids are used, whether given by you at home (orally) or by your veterinarian (injection), they should be given for as short a period of time as possible. The skin problems tend to wax and wane, so reoccurrence is unpredictable except in cases that tend to reoccur seasonally.

Since corticosteroids mask the problem rather than eliminate it, a reasonable effort should always be made to identify the cause and possibly use other types of treatment if effective. Here, too, a veterinary dermatologist may be extremely helpful.


  • If giving medication by mouth, follow directions exactly.
  • Realize the value of seeking a second opinion with a veterinary dermatologist for confirmation of the diagnosis and the most recent forms of treatment. Veterinary dermatologists are known as Diplomates of the American College of Veterinary Dermatology; your veterinarian can suggest a referral to one of these specialists. (Directory: www.acvd.org in North America; www.ecvd.org in Europe)


  • Do not use lotions, ointments, or other topical medications on the areas unless directed to do so by your veterinarian. Cats quickly lick off topical medications, and some may be harmful if swallowed.


  • If the areas do not heal with the prescribed treatment
  • If the condition reoccurs
  • If your cat is having difficulty eating due to eosinophilic granulomas in the mouth


  • •See the description of each form of eosinophilic granuloma complex in the About the Diagnosis section for initial symptoms, which are also the signs to watch for as an indication of recurrence if treatment is not working.


  • If your cat needs long-term corticosteroid treatment to control its skin disease, periodic testing, including blood samples, may be recommended to monitor for side effects.

From Cohn and Côté: Clinical Veterinary Advisor, 4th edition. Copyright © 2020 by Elsevier Inc. All rights reserved.

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