A common skin reaction pattern does not mean most cats have EGC. Precise prevalence figures for the different forms are not comprehensively known.
When to see a vet urgently
Contact a vet promptly if your cat develops any of the following:
- A mouth or tongue lesion makes eating difficult or your cat stops eating.
- An ulcer bleeds or swells rapidly, or your cat scratches extensive areas of skin open.
- A painful or discharging skin lesion occurs with obvious weakness or deteriorating general condition.
A persistent lip ulcer needs examination even when your cat does not seem painful. You can find a vet near you.
Overview
Eosinophilic granuloma complex develops with an abnormal immune response, most often associated with allergy to food, fleas or inhaled allergens. It is not contagious, but readily becomes chronic and recurrent. Lesions can occur in various places, including the lips, tongue, thighs, abdomen, head and between the toes.
In practice, EGC describes skin and mucosal reaction patterns, rather than one identical disease or one proven allergen in every cat. A cat may have one form or several simultaneously. A lesion may look like a large lump without being a tumour, but appearance alone does not exclude a tumour.
Not every form itches. An indolent ulcer or eosinophilic granuloma may cause few symptoms, while a plaque may produce intense licking and broken skin. A seemingly symptom-free lesion therefore needs examination just as an itchy one does.
Causes
- flea allergy, the most common cause;
- food allergy;
- atopic dermatitis, with reactions to pollen, mould or house dust;
- skin parasites, including mites and chewing lice;
- inherited susceptibility;
- immune response disorders.
An allergic background is common, but the trigger may remain unknown. A possible genetic contribution has been proposed, but does not establish an individual cat's cause. Nor should every parasite or immune mechanism listed be regarded as acting simultaneously.
Fleas may not be visible even when their bites matter: cats can lick them and their dirt out of the coat. Systematic, cat-suitable parasite control may therefore be part of investigation without a visible flea. Outdoor access and seasonal symptoms also help assess the importance of insect bites.
Risk factors
- cats not receiving control of fleas and other external parasites;
- cats with chronic allergies;
- young cats, with initial symptoms most often before 3 years old.
Young age fits some granuloma cases in particular, but EGC is not confined to cats under 3. Risk factors are not identical for every form, and comprehensive information on their independent importance is unavailable. A new lip or skin lesion in an adult cat is also examined rather than dismissed because of age.
Typical symptoms
EGC can appear in three forms:
- Eosinophilic ulcer, sometimes called an indolent ulcer: on the upper lip, forming an ulcer with raised borders that is usually neither painful nor itchy.
- Eosinophilic plaque: itchy red areas on the abdomen and inner thighs.
- Eosinophilic granuloma: firm yellowish-red nodules on the skin, tongue, lips or paws.
A plaque is a raised, often moist and hairless inflamed skin area. A granuloma may instead be an elongated lesion on the back of a thigh or a lump in the mouth. Lip ulcer edges can thicken and the chin may swell. Distinguishing forms helps describe the finding, but does not yet identify the allergy source.
General signs include:
- itching, licking and scratching;
- hair loss in affected areas;
- tenderness of ulcers and granulomas;
- a chronic, recurrent course.
Licking can continue unnoticed and cause an extensive hairless area. Photograph the lesion and record when it appeared and whether it changes during treatment. Slower eating, drooling or avoiding one side of the mouth is useful information too when lesions affect the lip or mouth.
Complications and consequences
- secondary bacterial skin infections;
- chronic non-healing ulcers;
- severe itching and reduced quality of life;
- rarely, malignant transformation of chronic ulcers.
The malignancy point requires qualification: EGC itself does not mean cancer, and an ulcer turning into cancer should not be regarded as its usual or established course. A tumour can resemble an inflammatory ulcer from the outset. An unusual, destructive or unresponsive lesion is therefore investigated with biopsy when needed.
A secondary bacterial infection may sustain damage, but bacteria are not necessarily the original cause. Interrupting scratching and treating possible infection are different from controlling the underlying allergy.
Diagnosis at the vet
- a clinical examination and characteristic skin lesions;
- cytology to detect eosinophils in lesions;
- a skin biopsy to exclude tumours and infections;
- a 6–8-week elimination diet and thorough flea treatment of all household animals, as allergy tests are unreliable in cats;
- skin scrapings and microscopy to exclude parasites and fungi.
Samples and investigating the allergic background
A cell sample can be collected by pressing a slide onto the lesion or using a fine needle in a lump, for example. Microscopy looks for other inflammatory cells and possible bacteria as well as eosinophils. Numerous eosinophils fit eosinophilic inflammation, but do not identify whether fleas, food or an environmental factor underlies it.
Skin scrapings and hair samples help investigate parasites. Ringworm testing may additionally require suitable laboratory methods, such as fungal culture; a negative scraping alone does not reliably rule it out. Biopsy helps distinguish similar-looking tumours and other inflammation, particularly with an atypical finding.
During an elimination diet, the cat receives only the agreed food and water. Treats, other animals' food and flavoured products can interfere with interpretation. Diet choice and adequate trial duration are agreed with the vet; the period mentioned above does not alone guarantee food allergy has been excluded.
If symptoms improve during the trial, controlled reintroduction of the original food may help confirm the link. Avoid repeatedly changing diets at random, as this makes it unclear what your cat responds to. The chosen food must also be nutritionally complete.
An allergy test alone does not diagnose the cause of EGC or atopic skin disease. Once other causes have been investigated, environmental allergen testing may be used, for example, to plan immunotherapy. Testing for this purpose differs from screening a cat without symptoms or confirming food allergy with a blood test.
Treatment and follow-up
Relieving itching while looking for the cause
Vet-prescribed glucocorticoids, for example, are used to control marked inflammation and itching. Another immune-modifying medicine, such as ciclosporin, may be selected in some situations. The medicine and route are tailored to the cat; treatment is not identical for every cat, and human products should not be used on your own initiative.
A confirmed bacterial infection is treated separately. With recurrent or severe infection, culture and susceptibility testing help select medication. Antibiotics alone do not remove flea or food allergy. If the underlying factor persists, inflammation may return even after successful symptom treatment.
The benefits and adverse effects of long-term medication are monitored. With glucocorticoids, for example, weight gain and other metabolic changes are watched for. Appropriate reviews and any laboratory tests are chosen individually. Do not change or stop medication on your own even when the lesion looks better.
What does a good treatment response look like?
As well as lesion size, follow-up assesses licking, scratching, eating and ordinary behaviour. Report entirely new lesions or recurrence too. A scab forming alone does not show that underlying inflammation or allergy is controlled.
Many cats become well with treatment, but some need a long-term plan. If response is poor, the diagnosis and how treatment is being carried out are reviewed. A lesion previously considered EGC may need a new biopsy or another investigation.
Prevention
- Provide regular control of fleas and other external parasites.
- Select an allergy diet under veterinary guidance.
- Limit contact with possible allergens.
- Treat and monitor chronic skin diseases.
- Reduce stress that worsens allergies.
Prevention targets confirmed or strongly suspected triggers. An allergy diet is not one uniform precaution for every cat; selection depends on a diet trial and findings. Parasite control considers contact animals and, when needed, environmental flea stages. Do not use a dog parasite product on a cat without confirming suitability.
Not every environmental allergen can be eliminated completely. Realistic care may therefore include both exposure reduction and symptom control. Reducing stress supports a calm routine, but does not replace treatment of a confirmed skin disease on its own.
Important for cat owners
Eosinophilic granuloma complex is a chronic allergic condition requiring attention and monitoring. Remember: recurrent itching, lip ulcers or skin plaques warrant assessment by a vet with expertise in skin disease. When the allergy's cause is identified promptly and treatment is appropriate, a cat can often remain free of symptoms for a long time with good quality of life.
This article provides general information and does not replace veterinary care. If you notice signs of illness in your cat, contact a vet.
Frequently asked questions
Is a cat's lip ulcer always an eosinophilic ulcer?
No. A typical appearance may raise suspicion, but other diseases and tumours can resemble it. An unusual or non-healing lesion needs further investigation. Lack of pain does not remove the need for examination.
Can EGC occur without itching?
Yes. Indolent ulcers and granulomas in particular do not always itch. Plaques are often clearly itchy. Treatment response is therefore also assessed from lesion size, skin condition and possible eating difficulties.
Can eosinophilic granuloma complex spread to other animals?
The eosinophilic reaction itself is not contagious. However, fleas may underlie it, and a similar-looking lesion may also result from infectious disease. The vet assesses parasite control and investigation needs for contact animals.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Eosinophilic Skin Diseases in Cats, Merck Veterinary Manual, accessed 2026-11-03.
- Eosinophilic Granuloma Complex, Cornell Feline Health Centre, accessed 2026-11-03.
- Eosinophilic Granuloma Complex in Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Figure 5: Clinical Presentation of the Feline Patient, American Animal Hospital Association, accessed 2026-11-03.
- Food Allergies, Cornell Feline Health Centre, accessed 2026-11-03.
- Fleas, Cornell Feline Health Centre, accessed 2026-11-03.
- Inhalant Allergies (Atopy) in Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Flea Allergy Dermatitis in Dogs and Cats, Merck Veterinary Manual, accessed 2026-11-03.