Feline eosinophilic granuloma complex is an umbrella term for three skin reaction patterns — indolent ulcer on the upper lip, eosinophilic plaque on the belly or thighs, and linear granuloma on the back of the leg or in the mouth. Almost always, these lesions are the visible tip of an underlying allergy (food, flea, or environmental). Most cats respond well to identifying and treating the allergy, with steroids or cyclosporine for symptomatic flares.
Last reviewed: May 2026
What Is Eosinophilic Granuloma Complex?
Feline eosinophilic granuloma complex (EGC) is a group of three related inflammatory skin patterns driven by eosinophils — a type of white blood cell linked to allergy. The three lesion types are the indolent (rodent) ulcer on the upper lip, the eosinophilic plaque (a raised, red, often weeping patch on the belly or inner thighs), and the linear granuloma (a yellow-pink raised streak on the back of the thigh, in the mouth, or on the lip). Approximately 1 to 4 percent of cats develop some form of EGC during their lifetime, and the three patterns can occur alone or in combination.
In the vast majority of cases, the lesions are a hypersensitivity reaction. The underlying triggers are flea allergy, food allergy, or atopic (environmental) allergy in roughly equal proportion, as described in Ettinger's Textbook of Veterinary Internal Medicine.
Recognizing the Three Patterns
The indolent ulcer is a smooth, red-brown crater on the upper lip near the canine tooth. It is usually not painful but can become deep over months. Eosinophilic plaques are intensely itchy raised red lesions, often on the belly or inner thighs, that look weepy and inflamed — cats lick them constantly. Linear granulomas appear as a firm yellow-pink streak on the back of one or both thighs, or as a swollen pad-shaped lesion on the lip or chin (sometimes called "fat lip"). Oral linear granulomas affect the tongue, palate, or pharynx and can interfere with eating.
About half of cats with EGC will show more than one lesion type at the same time. The lesions wax and wane with allergy exposure.
How Vets Diagnose EGC
Diagnosis is primarily clinical — the lesions have a characteristic appearance — confirmed by cytology of a swab or impression smear that reveals high numbers of eosinophils. A biopsy is occasionally needed to rule out squamous cell carcinoma (especially with an indolent ulcer), bacterial infection, or fungal disease. Bloodwork commonly shows eosinophilia, but a normal eosinophil count does not rule out EGC.
The real diagnostic challenge is finding the underlying allergy. The standard workup is strict flea control for 8 weeks, an 8-week elimination diet trial with a hydrolyzed or novel-protein diet, and (if needed) referral to a dermatologist for intradermal allergy testing or serology.
Treatment Options
Identifying and treating the underlying allergy is the only path to long-term remission. Aggressive year-round flea control (isoxazoline-class oral or topical preventives applied to all pets in the home) is the universal first step because flea allergy is the most common trigger. If flea control alone does not resolve the lesions in 6 to 8 weeks, an 8-week elimination diet trial follows.
For symptomatic flares, corticosteroids (oral prednisolone or methylprednisolone acetate injections) bring most lesions under control within 2 to 4 weeks, with structured monitoring of side effects in line with feline life-stage care (AAFP-AAHA Feline Life Stage Guidelines, 2021). Cyclosporine (modified, 7 mg/kg orally daily) is an effective steroid-sparing option for chronic cases. Targeted treatment of secondary bacterial infection (which is common in plaques) with antibiotics like amoxicillin-clavulanate also speeds healing. Feline pain and quality-of-life monitoring follow standard companion animal pain guidance (AAHA Pain Management Guidelines, 2022).
When to See a Vet
Not every symptom is a midnight emergency, but some warrant same-day attention and a few are true ERs. Use the lists below to sort which bucket you're in.
Call your vet today if:
- A new red, weeping, or ulcerated lesion on the lip, belly, or thigh
- Persistent licking or chewing at one body area for more than a few days
- A firm streak or "fat lip" appearance on the chin or lip
- Recurrent skin lesions in a cat with known flea or food allergy
- Bad breath or trouble eating combined with oral lesions
Go to the ER immediately if:
- Severe swelling of the lip, chin, or face that interferes with breathing
- Refusal to eat for more than 24 hours combined with oral lesions
- Bleeding ulcer that has grown rapidly
- Sudden whole-face swelling (possible severe allergic reaction)
- Lethargy, fever, or signs of systemic illness alongside the lesions
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Frequently Asked Questions
Is eosinophilic granuloma complex contagious?
No — EGC is not contagious to other cats or to humans. It is an allergy-driven inflammatory reaction, not an infection. The lesions can look concerning and may have secondary bacterial infection, but the underlying disease is the cat's own immune response and cannot be transmitted by contact.
How much does diagnosis and treatment cost?
Initial diagnostic workup with exam, cytology, and bloodwork typically runs $200 to $500. A biopsy if needed adds $250 to $600. An 8-week elimination diet trial costs $30 to $80 per month for prescription food. Treatment with corticosteroids is inexpensive ($10 to $40 per month), while cyclosporine for refractory cases is $50 to $150 per month. Referral to a veterinary dermatologist for allergy testing runs $400 to $900.
Will my cat have EGC for life?
Many cats have EGC long-term because the underlying allergy is hard to fully eliminate, but most can be kept comfortable and lesion-free with consistent flea control, an appropriate diet, and judicious use of steroids or cyclosporine during flares. Some cats with food-driven EGC clear completely on the right hypoallergenic diet and never have another lesion.
Are steroids safe long-term for cats with EGC?
Short-term steroid pulses are generally safe and effective. Long-term daily steroid use in cats can predispose to diabetes, urinary tract infections, and skin thinning. When chronic immunosuppression is needed, cyclosporine is often preferred. Modified-release methylprednisolone injections are also useful when oral dosing is difficult, but spacing should be as long as the cat allows.
Can EGC be confused with cancer?
Yes — particularly the indolent (rodent) ulcer on the upper lip, which can resemble squamous cell carcinoma. A biopsy is recommended whenever an ulcerative lip lesion does not respond to a focused EGC treatment plan within 6 to 8 weeks, or when there is rapid growth, deep ulceration, or facial bone involvement. Catching squamous cell carcinoma early significantly improves treatment options.
Still Not Sure if Your Cat Needs a Vet?
When you're not sure if this is wait-and-see or call-tonight, Voyage AI Vet triages in under 2 minutes. Describe what you're seeing in chat, share photos of any lip, belly, or thigh lesion, or hop on a live video call if you want a second pair of eyes. Every answer comes with citations to the actual veterinary literature it's pulling from — so you see exactly where the guidance comes from, not just a chatbot's word.