Feline Eosinophilic Granuloma Complex (Indolent Ulcer, Plaque, Granuloma)
The feline eosinophilic granuloma complex brings together three skin conditions in cats: an indolent ulcer on the lip, eosinophilic plaque, and eosinophilic granuloma. These are grouped under one name because they share a common feature—an...
What is it?
The feline eosinophilic granuloma complex brings together three skin conditions in cats: an indolent ulcer on the lip, eosinophilic plaque, and eosinophilic granuloma. These are grouped under one name because they share a common feature—an influx into the skin of particular white blood cells called eosinophils—and because the same cat may develop several of them, at the same time or over the years.
This is not a disease with a single cause, but rather a way the cat's skin reacts. In most cases, this reaction is triggered by an allergy: to flea bites first and foremost, but also to environmental factors or food.
The lesions respond well to treatment, but they return as long as the underlying cause is not identified and controlled. This is why treating the wound alone is not enough—the allergy that sustains it must also be found.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Indolent ulcer: a well-defined wound, reddish-brown in color, at the edge of the upper lip, often opposite the canine tooth, on one or both sides. It may look serious, but it often does not bother the cat, does not bleed, and does not itch.
Eosinophilic plaque: a raised, raw, red and weeping area, often on the belly or inside the thighs. It itches greatly: the cat licks it constantly, which keeps it irritated.
Eosinophilic granuloma: a firm nodule or ridge under the skin. It sometimes appears as a raised streak on the back of the thighs, a swollen chin, or small masses in the mouth, on the tongue or palate.
Older lesions may become infected, become more painful, and heal slowly.
The cat generally remains in good overall condition. A cat that stops eating, loses weight, or becomes depressed should be evaluated for other conditions.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The most common cause is an allergy: allergy to flea bites above all, allergy to environmental elements (pollen, dust mites), or food allergy.
Bites from other insects, such as mosquitoes, can also trigger lesions, particularly on the nose and ears.
A familial predisposition has been described in certain cat bloodlines, particularly for early-onset forms.
In some cases, no specific cause is found despite investigation.
Allergy to flea bites, particularly in a cat not treated regularly for fleas.
Known allergy to environmental factors or food.
Cat that goes outdoors and is exposed to insect bites.
Granuloma more commonly affects young cats.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian examines the lesions, their location and appearance: the lip ulcer, the belly plaque, and the streak on the back of the thighs are fairly characteristic.
The vet checks for fleas or flea dirt and asks whether the cat and other household pets are treated regularly.
A sample taken from the lesion surface, viewed under the microscope, shows eosinophils and any associated infection.
A biopsy, a small skin sample taken under anesthesia, is recommended when there is doubt about a tumor: a sore on only one side of the lip that deepens or grows quickly should always be tested.
Searching for the cause is then done in stages: strict flea treatment for all animals, then, if lesions return, an elimination diet for several weeks, then screening for environmental allergy.
Treatment
Treatment combines two approaches: calming the lesions and controlling the cause.
For the lesions, the veterinarian usually prescribes an anti-inflammatory from the corticosteroid family, sometimes another medication that modulates immunity when corticosteroids are not suitable. An antibiotic is added when the lesion is infected, which is common for the ulcer and plaque.
For the cause, regular flea treatment for all household animals is the first step, even if no fleas are visible. An elimination diet is offered if food allergy is suspected.
Lesions that resist or keep returning warrant more thorough testing.
Do not give the cat human medication or ointment without veterinary advice: several are toxic to cats, and improper corticosteroid therapy can mask a tumor or worsen an infection.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Regular flea treatment for all dogs and cats in the household significantly reduces the risk of recurrence in a flea-allergic cat.
Once the underlying allergy is identified, managing it long-term is the best way to prevent lesions from returning.
Watch the lip, belly, and back of the thighs: a lesion caught early is easier to treat.
Possible complications
Bacterial infection of the lesions, which become more painful and take longer to heal.
Repeated recurrence as long as the underlying allergy is not controlled.
A granuloma in the mouth may interfere with eating.
A very old and neglected lip ulcer can disfigure the lip; it can also be mistaken for a tumor, which is why examination is important.
When to see a veterinarian
A wound or swelling appears on your cat's upper lip.
Your cat constantly licks a raw area on the belly or thighs.
A firm lump, a raised streak, or a swollen chin appears.
A previously treated lesion returns.
The lip sore is on one side only and deepens or grows quickly: consult within a week.
Your cat is not eating because of the wound: consult the same day.
Prognosis
Lesions generally respond well to treatment.
Long-term prognosis depends mainly on the cause: when the underlying allergy is identified and controlled, recurrence becomes rare; otherwise, it is frequent and requires repeated treatment.
Frequently asked questions
Is the wound on my cat's lip cancer?
Most often no: an atonic ulcer is an inflammatory lesion. But skin cancer can resemble it, especially in an older cat, when the wound is one-sided and deep or spreads quickly. In case of doubt, the veterinarian performs a biopsy to settle the matter.
Is it the same thing as an allergy?
Not exactly. The eosinophilic granuloma complex is a skin reaction; allergy—to fleas, environmental factors, or food—is its most common trigger. Treating the lesion without investigating the underlying allergy risks recurrence.
How do you distinguish it from ringworm or scabies?
Ringworm typically causes round, hairless patches, while mange causes intense itching with crusting on the ears and face, often affecting multiple animals. The eosinophilic complex is recognized by its typical lesions: lip wounds, raw patches on the belly, and nodules or streaks on the thighs. Only samples can provide certainty.
Can a cat have a flea allergy even if it doesn't have fleas?
Yes. An allergic cat grooms excessively and eliminates fleas; just a few bites are enough to trigger lesions. This is why the veterinarian recommends rigorous flea treatment for all animals, even when no fleas are visible.
References
Content reviewed by the TunisieVet editorial team · Updated 30 October 2026
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