What Is That Painful-Looking Red Wound on my Cat's Lip Or Body !

Eosinophilic Granuloma Complex aka Lick Granuloma, EGC, FEGC

Ron Hines DVM PhD

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Is There More Than One Form Of Eosinophilic Complex ?
Ulcer(s) On Your  Cat's Lip
Inflamed Areas In Your Cat's Mouth
Eosinophilic Plaque
Miliary Dermatitis
Inflamed Areas On Your Cat’s Foot Pads and Paws
Mosquito Bite Hypersensitivity
Inflammation Of Your Cat’s Cornea
Inflamation Of The Digestive Tract
Eosinophils - Where They Come From - What They Do
How Old Are Most Cats With This Problem ?
Does EGC Affect Male And Female Cats Equally ?
Is Your Cat's Genetics Involved ?
How Will My Vet Be Sure Of The Diagnosis ?
Do Veterinarians Know What Causes EGC ?
What Are The Best Treatments For My Cat ?
Scientifically Unproven Remedies

Will My Cat Face This Problem Again ?

If your veterinarian experimentally tries Apoquel for this problem in your cat, I would appreciate an email informing me me of the results
You can read another excellent review of this perplexing disease here

This mysterious disease of cats goes by many names : rodent ulcer, lick ulcer, eosinophilic granuloma disease, eosinophilic complex etc., and despite the tremendous progress that has been made in veterinary medicine, why it occurs remains an enigma. The less one understands a disease, the more names veterinarians tend to give to them. EGC is probably the leader of the pack in that respect.

Its causes remain hard to pin down. Guesswork is the norm and hard facts are few. In many cases, the lesions (wounds) spontaneously vanish with time. In some cases, a single episode occurs, vanishes or responds to treatment once in a cat’s life, in others, the lesions are stubborn, resist treatment or return again and again. In some cases; cats are very itchy (pruritic), in others, the lesions are ignored. They can come up quite suddenly or develop gradually over an extended period of time.
As pathologists began to examine these lesions they noticed that they all contained abnormal numbers of inflammatory cells called eosinophil
s, accompanied by neutrophils and scar tissue. In my practice, the lip form is the most common. But a second form that causes patches (plaques) or lightening-like (linear) lines of inflammation on the cat’s body is said to be more common. In a more rare form, the cornea of the cat's eye can be affected.

Is There More Than One Form Of Eosinophilic Complex ?

Yes. As I mentioned, there are many; and veterinarians have divided them up according to their location on the cat’s body. These divisions are arbitrary, overlapping and can be confusing with no more than a general agreement among veterinarians as to terminology. Cats can have several of these forms of EGC occurring at different places at the same time - or in succession. What they all have in common is that the pet's eosinophils are overabundant within them.

Ulcer(s) On Your Cat's Lip  = eosinophilic ulcer, indolent ulcer, rodent ulcer

This is the most striking way that EGC affects cats. Puffy, thickened ulcers appear on the margin (edge) of the cat's lip. Usually, it is on one side of the pet's upper lip (80% of the time) - somewhere between the cleft below it's nose and its large canine tooth. It can be on both sides as well. The ulcers can be small, or the entire upper lip can be involved and, with time, permanently disfigured. They can bleed - but not profusely. With time, these ulcers often become concave (eroded in the center) with a firm-to-hard feel. There is a lot of color variation, but the edges are often darker reddish brown than the center, which has a glistening pink to yellow or whitish tone. (clients used to bring these cats to me thinking this was a burn from chewing on an electrical cord.)

It is said by some that these lesions are not painful and do not appear to itch. But cats with this problem always look dejected to me and they are certainly painful for me to look at.

Some of these cats are reluctant to eat.

Farmers saw this problem in their barn cats, got the mistaken idea that they were associated with eating rodents - hence the name, rodent ulcer. Wounds that will not heal are called indolent. >

In rare long-standing cases, the lymph nodes on the neck of these cats can be enlarged (peripheral lymphadenopathy).

In some cats, the problem is not confined only to the upper lips but involves the lower lip and chin giving the cat a "fat lip" or pouting appearance and in some the tongue and roof of the mouth are involved as well.

With this form of EGC, some veterinarians inject their medications directly into and surrounding the lip lesions themselves. The dense scarring that accompanies this problem can make that difficult.
 
Inflamed Areas In Your Cat's Mouth =The oral form of EGC

Sometimes, these lesions begin in the cat's mouth initially. In other cases, the lip form precedes oral lesions. Often it is the upper portion of the mouth that is affected - the soft palate, the tongue and even the pharynx as far back as the frenulum.

Naturally, these poor cats usually drool (ptyalism) , have a strong fetid breath (halitosis), are reluctant to eat and have difficulty swallowing (dysphagia).

It is always a good idea to check a pet with lip ulcers to be sure none become present in its mouth as well. These lesions, and cat mouths in general, are always a source of dangerous bacteria if you are bitten, so it is wiser to let your veterinarian do the inspection.

Not every cat with the symptoms I described has EGC lesions in its mouth. There are a variety of non-EGC problems that occur in the mouth of cats and they can occur when EGC is present elsewhere or in cats that do not suffer from EGC.

Mouth infection in your cat (stomatitis) cause by bacterial or fungal infections and not by EGC can also cause halitosis, drooling and mouth pain. Cat that have been in car accidents often have fractures of the jaw or broken teeth that cause similar signs. Cats with heavy tooth tartar or resorptive dental lesions also show similar symptoms. Cats can have things lodged in their mouth or upper throat. (when a playful cat swallows sewing thread, sometimes the needle at the end gets lodged and infected in its mouth)

Cats in kidney failure (renal failure) are more prone to many forms of non-EGC stomatitis. The general debility of common cat viruses, feline leukemia and feline immunodeficiency as well as calicivirus, also make cats more susceptible to stomatitis.

Immunosuppressive drugs, like cyclosporine (Atopica) can also cause mouth inflammation.

Elderly cats are susceptible to tumors (adenocarcinomas) of the mouth. Those need to be ruled out too (with a biopsy).

You can read more about the various problems, including Eosinophilic complex, that can affect your cat's mouth here.

Eosinophilic Plaque = Linear Granuloma or just Eosinophilic Granuloma, collagenolytic granuloma

Most veterinary practices in the USA and Western Europe find this form of EGC to be the most common form in their patients. We usually see this in younger cats (~1.5-6 years old).

The body sores these cats develop are either roughly circular or streaks and lines. There may be only one, or there may be several. They are slightly raised and tend to be a red to salmon pink in color.  They look somewhat like the road rash one suffers when falling off a moving bicycle or skate board. They can form anywhere on the cat's body; but the ventral (lower) abdomen and rear thighs are common locations. When it affects the cat's rear or front legs, it is often on the inner (medial) side. The cat's neck, throat and anal area can be other sites for the problem.

They often itch intensely causing the cat spends its time licking and causing the wounds to ooze fluid (blood serum), glisten  and loose the hair that once covering the area. The rough tongue of housecats quickly make these lesions raw and angry if the cat is not placed in some sort of restraint (Elizabethan collar). Despite their intensity, I have never seen bacterial infections associated with these open ulcers to be more than a superficial, minor problem. 

Biopsies of these areas show that they are heavily infiltrated with eosinophils. Neutrophils often congregate in these areas as well and, although not recognizable on routinely processed tissue, mast cells have also accumulated in these areas. (ref)

If your veterinarian stains and examines glass slides that were pressed onto the affected area, bacteria, and remnants of eosinophils, neutrophils might be seen as well.

In this form of EGC, the cat's blood is more likely to have circulating eosinophils that are more numerous than normal.  It is also common for the lymph nodes that drain the affected areas to be moderately enlarged (regional lymphadenopathy).

This , and the miliary dermatitis form form of EGC are the ones most likely to be associated with flea infestation. Many improve without medication when the cat is moved to an environment that is totally free of fleas.

Miliary Dermatitis

Miliary dermatitis is another way that the skin form of EGC can present itself. In this form, the skin inflammation occurs in many small reddened pox-like areas rather than large plaques. These areas quickly become crusty.

This form is usually quite itchy and it is common for the cat's hair coat to be quite thin as a result of all the licking they do (cats can develop hair balls or constipation due to all the ingested hair).  

In some cases of miliary dermatitis, the red papules are not as apparent as in others and the symptom most noticed by owners is a patchy, thin hair coat. Those cases need to be differentiated from stress induced over grooming (psychogenic alopecia although wikipedia is confusing the two issues). When amytriptiline is helpful, I am always suspicious that psychogenic alopecia, rather than EGC  is the underlying problem. Sarcoptic and notedric mange can also be confused with miliary dermatitis caused by EGC.

When it is not, flea allergy, atopic allergies and food allergy are the first things that come to mind.

Cats that are positive feline immunodeficiency virus (feline AIDs) or for feline leukemia can also present with perplexing skin disease. So all cats with skin problems ought to be tested for them as well.

Eosinophilic Granulomas On Your Cat's Foot Pads and Paws

In some cats, the pads of the feet are the site of Eosinophilic granuloma complex EGC.

Those pets are often brought to me because they are limping. It is usually a young cat (under 2-3 years old). On examination, one of more of their foot pads is inflamed, swollen, damp and painful. The foot often has an unhealthy odor and it is not uncommon for them to be ulcerated as well.

 When cats come in with tender or swollen paws, broken toe nails, evidence of a poorly performed declaw operation or a penetrating thorn always need to be looked for. Paws are also a common site for abscesses that occur after cat fights. Those cats are often running a fever if the abscesses resulting from the fight has not begun to drain. Infected feet are often warm to the touch. They are not when EGC is the cause.

When the footpad form of EGC has just begun, pain and a loss of toe pad pigment can be the only signs. It is also common for there to be cracks in the foot pads. Of course, if EGC lesions are present or begin to occur at other locations on the pet’s body, what you are seeing in its paw is most likely part-and-parcel of the same underlying disease.

When the footpad form of EGC occurs, a cat-litter sensitivity has occasionally been implicated. So a change in your cat's litter is always a simple and prudent thing to do. The same goes for cleaning products used around the home.

Cats occasionally suffer from a footpad condition that appears quite similar to EGC.  It is called Plasma Cell Pododermatitis and it too appears to have a basis in your cats immune system. However, when biopsies of the affected paw(s) are examined, plasma cells, (another cell of your cat's immune system) rather than eosinophils are found in excess. You can read about that condition here.

No matter which of the two conditions are diagnosed, an FeLV and FIV test would be a good idea if they have not been performed recently.

Mosquito Bite Hypersensitivity

Some cats develop distinctive raw, inflamed areas on the bridge of their nose that also contain eosinophils. This is the least common of the syndromes that are generally included in ECG. It is thought to be due to an allergy to components of the saliva that mosquitoes leave behind after drawing blood. The edges of the ears and other areas on the cat with scant hair are also susceptible.

When mosquitoes are the source of your cat's problem, you might notice that lesions only occur during mosquito season.

There are veterinarians that believe that a mosquito bite allergy can be the cause of the other forms of EGC as well. So keeping your cat indoors is a wise move when dealing with any form of EGC.

Bacterial Infections that follow EGC-related nose problems can obscure the microscopic changes that veterinary pathologists use to diagnose EGC. But be suspicious of EGC or an autoimmune disease when your pet's nose becomes inflamed for no apparent reason. As with the other forms of EGC, an FLV/FIV test is advisable.

You can read an article about Eosinophilic Complex related to mosquitoes here.

Eosinophilic Inflammation Of The Cornea Of The Eye = Eosinophilic karatitis

Eosinophilic keratitis is not often included in the diseases thought to comprise eosinophilic complex. I  deal with it here simply because eosinophils appear in great numbers in the affected eye tissue. In this problem, the outer clear cornea of the cat's eye develops a amber pink-to-grey raised, roughened area - usually near the cornea's center. Usually, only one eye is involved. Unlike simple cuts and abrasions to this area, Eosinophilic keratitis lesions fail to heal with time, antibiotics or protective eye drops.

Unlike the other forms of accepted EGC disease, the herpes 1 (rhinotracheitis, FHV-1) virus is thought by many to be the underlying cause for these eye lesions. This is the same virus that causes discharges, conjunctivitis, sneezing and sometimes hypersalivation and coughing in cats when they are initially infected. You can read about that virus here . However, evidence of FHV-1 virus can not be found in all cases of Eosinophilic keratitis. (ref)

Most of these cases respond well to topical steroid-containing eye drops (eg prednisolone or dexamethasone) and some to anti-herpes medications (eg trifluridine, Viroptic). But the cats must be watched closely to be sure a rupture (descemetocele) does not occur in the cornea until it has healed.

When medications are ineffective, surgery to scrape the lesion free of debris and dead tissue, cryosurgery or radiation therapy is sometimes required.

You can read about these eosinophilic eye lesions and their treatment here.

Eosinophil-related Problems Of Your Cat's Digestive Tract = Eosinophilic enteritis, EE

As with the eye form, eosinophilic digestive tract problems are not an accepted form of EGC. But occasionally, the inflammation associated with eosinophils occurs in the walls of your cat's stomach or intestine. When this occurs the main signs are diarrhea, vomiting and weight loss. Although it shows many similarities to EGC, this particular problem is usually considered as a form of inflammatory bowel disease IBD.

Which signs predominate depend on which portion of the cat's digestive tract is most inflamed. Diagnosis requires a biopsy sample.

This is not a common disease in cats but it has occurred in felines 1.5-11 years of age.
Food allergies, autoimmune disease and pre- cancerous changes within the bone marrow that produce eosinophils are all suspected causes. Like EGC, corticosteroids, diet changes and, when required, immunosuppressive agents like cyclosporine or chlorambucil are treatment choices.

A Bit About Your Cat 's Eosinophils - Where They Come From - What They Do

Eosinophils are one of the soldier cells of your pet’s immune system (an army of neutrophils, eosinophils,macrophages, dendritic cells, natural killer cells and basophils). They form in the pet's bone marrow and are released into its blood stream. We believe that the eosinophil 's normal job is to destroy parasites. Eosinophils do not stay there long. Soon, they migrate into sold tissue throughout your pet's body. There, they remain "in touch" with another cell of the pet's immune system, the mast cell. When a mast cell "believes" that it has recognized a foreign invader, something that does not belong in the pet's body and to which prior antibodies (IgE) were produced, it releases chemicals designed to alert nearby eosinophils and summon more of them. Those eosinophils, in turn, release chemicals designed to destroy the invader. That is just fine when the foreign substance is a parasite; but when it was summoned due to an IgE that was mistakenly produced against, say, pollen, a food protein, flea saliva, etc. ; the chemicals that the eosinophil releases cause damage to the pet's own surrounding tissues. The non-threatening things in the pet's environment that can cause these "mistaken IgEs" are called allergens. When your pet has them, it has become allergic. Because parasites are often located or enter through the body surface, eosinophils tend to hang out just under the skin and glistening membranes that line entrances to the body. (ref)    (I gave you a very simplistic explanation. If you want the real story, go here.)

How Old Are Most Cats When They Begin To Develop  Eosinophilic  Problems ?

The majority of cats that develop EGC do so between 2 and 6 years of age. Some develop it earlier, but it often takes a year or three for cats to develop severe enough allergies for owners to take notice.

Does EGC Affect Male And Female Cats Equally ?

I have not noticed that male or female cats have a higher incidence of EGC in my client's cats. But some veterinarians find that they see the problem more frequently in female cats. Cornell Veterinary School's handout out EGC suggests that  (ref) ; but when the medical records of 55 cats admitted to the Cornell school with EGC or the 1407 with assorted skin problems were examined, male cats predominated. (ref)   So your cat 's sex is probably irrelevant.

Is Your Cat's Genetics Involved ?

One respected textbook states that Siamese and siamese crosses are at a higher risk of EGC (ref) but the Cornell study found that of Siamese-type cats, only Himalayans had that increased risk. (repeat citation)

But veterinarians know that genetics can occasionally play a part in Eosinophilic diseases. In dogs, Siberian huskies account for 76% of the cases of Eosinophilic granuloma and one report in 2005 found a particularly high number of kittens from a specific breeder later developed EGC even though they had completely different lifestyles and diet at their new homes. (ref)

How Will My Veterinarian Be Sure Of The Diagnosis ?

When your cat 's visual symptoms and history are typical of EGC, the diagnosis is rather easy for your veterinarian.

Occasionally, questions remain. In that case bloodwork might show increased numbers of eosinophils in your pet’s circulation (eosinophilia) , adding to suspicion that EGC is the underlying cause of your pet's skin condition (however, many cats with EGC, have no increase in their blood eosinophil numbers). Bloodwork, including blood chemistry values also helps veterinarians rule out other possible underlying causes.

In other unusual cases, it takes a biopsy - a small snippet of tissue from the lesion - to confirm that EGC is your cat's problem. (Veterinary pathologists rely on the over abundance of eosinophils in the biopsy specimen to confirm that your cat has EGC. However, there are occasional cases where it is primarily mast cells that are present (ref)Treatment for those cats and probably causes are the same as for EGC.)

Whenever your veterinarian is worried about a possible tumor masquerading as EGC (particularly when the problem is in the mouth), a biopsy examination is a wise choice to set everyone's mind at ease.

When neither is present in the biopsy, the pathologist will be looking for evidence of fungal skin disease, tumors, foreign bodys, etc.

Allergy testing for fleabite sensitivity, food allergy or other allergens is rarely helpful. Many cats that never develop EGC come up positive on those tests. The only valid way to rule out those common allergies is to remove them from your cat 's environment and see if the pet improves. (ref)

Most veterinarians will follow the procedures outlined in an article which you can read here.

Do Veterinarians Know What Causes This  Problem ?

Most veterinarians will tell you that EGC is a "hypersensitivity reaction" or "allergy". That is almost certainly true - since that is what activated eosinophils cause. Beyond that, everything is much less certain. There are probably very many "triggers" that allow this disease to occur.

Here are what most of us think the common causes are :

A Flea Allergy

Many cases of Eosinophilic complex go away when your cat is no longer exposed to fleas.
We believe that some cats become more sensitive to components of flea saliva than others. Some of those cats develop intense itching and subsequently damage themselves scratching (flea allergy dermatitis, FAD); but others seem to go on to develop one of the various forms of Eosinophilic Complex. Their rough tongue can cause more damage than the allergic reaction itself.

It was recently discovered that parasite bites can cause allergies to things other than the parasite that bit them. Children that have been bitten by ticks appear more prone to develop food allergies. (ref)

Might tick, or flea saliva be doing something similar to sensitize cats? Might those parasites be carrying a pathogen we do not know about? We do not know. 

Fleas are not the only skin parasite capable of causing itchy open lesions on cats. Be particularly suspicious of them if more than one cat in a household has the problem. (ref)

Food Allergies

Most veterinarians believe that food allergies account for some of the cases of EGC that they see. This is particularly true of the miliary dermatitis form. (ref)

These are cats that do not seem to have a particular time of the year when they are prone to EGC problems. Some have other indications that their diet is not optimal for them, such as periodic diarrhea, vomiting, hives, etc. A food allergy diagnosis is probably more likely when EGC problems develop on multiple areas of the body and when itching is significant.
But one needs to be sure that the hair loss and licking is not a simple reaction to stress occurring in the cat 's life (psychogenic alopecia or hair loss).

The trial diet is fed for at least 6 weeks. The duration needs to be extended if the secondary skin or ear infections have not been cleared yet or if the cat shows improvement but not complete resolution of clinical signs after 6 weeks. (ref)

Contact Sensitivities

Cats can become sensitive to contact with things in their environment. So some vets suggest changing from plastic to stainless steel food dishes, changing brands of litter, laundry detergent, etc. Some veterinarians have seen something similar to EGC develop at the site where flea-control products have been applied to cats (imidacloprid, Advantage, fipronil, Frontline).

Inhaled allergies = atopy, atopic skin disease

In dogs, far more are allergic to things they breath than things they eat. Less is known about cats. Veterinarians an owners tend to focus on food allergies and topical (contact) allergies because those are the only ones that can be readily eliminated from the pet's life.

Vets do try to give desensitization shots to allergic cats with rather mixed results. Some claim an optimistic 60-70% success rate after 3-12 months of injections. I am less optimistic about the success rate when dealing with EGC. (ref)

Some of the antigens that have been implicated or suggested are house dust mites, pollens and molds.

Perhaps Sometimes An Autoimmune Or Misdirected Immune Disease ?

An older research study found that 68% of cats with Eosinophilic granuloma complex that they examined had antibodies in their system that were directed against the cat 's own skin. (ref)  However, they were unable to determine if preexisting EGC was the cause of this antibody or if the antibody was the cause of EGC. This sort of phenomenon is common in humans. (ref)

Another more recent study found indications that some cats with EGC might have actually become allergic (developed antibodies against) to their own saliva ! (ref) Who knows ?  

Here is another interesting tidbit :

Human dermatologists know that cats are the most antigenic of our pets when it comes to making people allergic to them. They have also noticed that people who are allergic to cats are more likely than others to be allergic to eating pork. It is called the pork-cat syndrome. (ref)

A few months ago, (today is 09/01/13) a group of doctors in Virginia noticed that an unusually high number of their  patients who had developed allergies to a variety of red meats - including pork - reported that itchy tick bites had occurred before they became sensitive to red meat. ( repeat ref)

Could flea or tick bites cause something similar in your cat? No one knows; but perhaps including a chicken or turkey-based diet in your cat 's EGC treatment plan would not be a bad idea. Consider making it yourself. (ref)

Could  Other Infectious Organisms Be Involved ?

The Feline herpes1 virus

In 1999, two Washington State veterinarians reported that they had identified portions of the Herpes-1 virus in the Eosinophilic lesions on the faces and nose of cats. That is the same virus that cats routinely  get vaccinated for to prevent respiratory disease (rhinotracheitis, cat flu). (ref) Herpes-1 virus was also identified in Cheetahs that suffered from EGC. (ref)

But in 2010, veterinarians at the University of Sydney found only 2 out of 30 cats with EGC-like disease to be positive for herpes-1. They did point out that herpes-1 should be considered when cats do not respond to corticosteroids treatment for EGC. (ref) Veterinarians in Italy came to the same conclusion. (ref)
 
When Eosinophilic disease affect the
corneas of the cat's eye, herpes-1 is a more accepted cause. (repeat ref)

The problem with linking the Herpes-1 virus to Eosinophilic granuloma complex is that so many cats are positive for the virus. So we are never really certain if finding evidence of the virus has anything to do with the skin disease we are treating. Once a cat has gotten over a Herpes-1 infection, it probably carries that virus for the rest of its life. (ref)   Things like stress, corticosteroids or other viral infections like FIV can weaken the cat 's immune system enough to reactivate the virus once again. After one week at an animal shelter half the cats are shedding Herpes-1. (ref)  

The Feline Immunodeficiency Virus

FIV virus does not cause EGC. But chronic inflamed areas of the mouth (chronic ulceroproliferative stomatitis) that might be confused with EGC are a very common symptom of FIV virus infection in cats. (ref

So an FIV/FLV test on all cats with mouth infections (stomatitis) or mouth ulcers is always a wise decision before treatment begins.

Calicivirus

Feline Calicivirus does not cause EGC. But it is another infection that needs to be considered when dealing with ulcers within a cat 's mouth or on its tongue or skin because that virus has the potential to cause them as well. (ref)

"Idiopathic" simply means we do not know the cause.

What Are The Most Successful Treatments For My Cat ?

Corticosteroids

Almost all treatment plans for initial bouts of Eosinophilic granuloma complex will require a corticosteroid medication. You probably know the drawbacks of long-term corticosteroid administration - but one course of corticosteroids, given in appropriate amounts, is not going to harm an otherwise health cat. It will give your cat almost immediate relief, allow the lesions to heal and give you and your veterinarian time to devise a long-term plan. While your cat is receiving that medication, its appetite and thirst will increase. Limit its food to prevent weight gain - but do not limit its water intake.

It is true that some cats with the skin form of EGC will improve if they are placed in Elizabethan collars with, or without topically applied corticosteroid sprays and ointment. I just find them too stressful for most cats to wear. 

Eosinophils quickly dissipate when exposed to corticosteroids. So when oral or injectable corticosteroids, given at acceptable doses, fail to promptly improve the problem a biopsy is a wise choice. Perhaps you are dealing with a problem other than Eosinophilic Granuloma.

With repeated relapses of EGC, corticosteroids can be less effective and the dose required may be considerably larger. In those cases, be sure that you have tried all other common treatments. When you have and the EGC problem persists, don't feel guilty about it - many humans, faced with autoimmune disease or organ transplants take corticosteroids for their entire life. They have just made the decision that the potential side effects of corticosteroid medications are less important than what they would be facing without them.

Many veterinarians rely on one or two injections of a long acting corticosteroid called methyprednisolone acetate (Depomedrol or just "Depo") to bring EGC lesions under control. If further corticosteroids are required, they are generally given in tablet form. Prednisolone is the most common one used. Generally , those tablets are not given daily - at least not after the first 7 days. The break between tablets is to help prevent a decrease in your cat's adrenal glands to produce its own natural corticosteroid, cortisol. Others prefer triamcinolone. All cats receiving long term corticosteroids need close monitoring and periodic check ups to catch potential side effects early.

When you cat is receiving long-term corticosteroids, its appetite will probably increase and it may gain weight. Make a determined effort to avoid that weight gain by feeding only the amount of food (calories) that maintains a healthy body weight. Fat cats are at a much higher risk of developing diabetes. (ref)

Topical Corticosteroid Sprays Creams And Lotions

I have not found them very effective. First, cats tend to lick them off quickly. Second, they do not seem to penetrate deep enough within the lesions to resolve them.  (Topical beclomethasone with antibiotic [eg GentaSpray, etc] can be somewhat helpful in the miliary and plaque form of EGC when excessive licking is the only sign of an early flare up if you can keep a cat from licking it off and when the alcohol base of some of these spray products does not irritate their skin too much

A Very Aggressive Attempt At Flea Control

We know that fleas and Eosinophilic Granuloma Complex go hand in hand. (ref)  So Flea control should always be part of your plan. It means keeping you cat indoors. It means applying one of the newer monthly flea control products (imidocloprid, fipronil, selamectin, spinosad, etc.)  Even if you never see fleas on you pet, consider an aggressive flea control program essential. It is quite easy to miss a flea or two that is present on your cat now and then. The itching - an allergic response to a bite - can last long after the flea has left. If you ever see tapeworms (ref)  in a cat that is not a hunter, just assume fleas are present in its life. That is how the most common one is spread.

Fleas can be exasperating. There are many veterinarians who suggest these flea products be applied more frequently than monthly. But I generally assume there is a break somewhere in your control system if the products do not last a month - unless the house is just super-infested with fleas, flea eggs and flea pupae. Every pet in the household (dogs,cats, ferrets, bunnies) must be treated with an appropriate product – not just the one with EGC.  

Lower Stress In Your Cat's Life

Stress makes most diseases worse. The biggest stressor for cats are other cats in the household. This is particularly true in cats that develop skin disease due to over grooming (psychogenic alopecia/dermatitis). Try to remember that what you and I find stressful or enjoyable might be quite different than your cat 's feeling in the same situation.

A Trial Course Of Antibiotics

Very few veterinarians believe that EGC is caused by bacterial infections. It is true that almost all EGC are colonized by bacteria - but those bacteria are usually just a superficial layer living within dead and devitalized tissue.

Still, there are reports of cats with EGC improved when antibiotic was the only treatment they received. (ref)

Another rational for giving antibiotics is that corticosteroids, when given, lower resistance to infection and an antibiotic "cover" in those situations is desirable.

Besides the Clavamox/Augmentin (Amoxiciilin & Clavulanic acid) antibiotic mentioned in the prior reference, veterinarians often administer periodic Convenia (cefovecin) antibiotic injections or rely on doxyclcyline. Doxycycline is in the tetracycline family of drugs; and they are known to sometimes have beneficial effects beyond their ability to kill bacteria. (ref)     Pets receiving doxycycline tablets or capsules need to then be given water or food by hand immediately thereafter to prevent the doxycycline from causing inflammation of their esophagus.

A Trial Period On A New Diet

Changing your cat 's diet for 8-10 weeks is something simple you can do that has no down side. I generally suggest you make the diet at home if you have the time. I would base it on cornish hen chicken or turkey to begin with and feed without supplements or additions (buy a commercial meat grinder and include the finely ground up bones to provide adequate calcium).  If the diet improves your cat's health, start adding necessary vitamins and other ingredients after that one-by-one, no more than one added per week, and observe if the problem returns. You never know how those supplemental products will affect them so I begin without them. You can read some suggestions on preparing a diet for your cat here. I would not feed the home-prepared diets raw - particularly if the pet is also on corticosteroids as those medications can decrease its ability to handle things like toxoplasma and salmonella.

Alternatively, use one of the hypoallergenic cat diets in which antigenic particles have been destroyed (hydrolyzed protein) such as HA, z/d etc. However a lot of cats wont eat it.

Avoiding Contact Allergens

Pet owners and some veterinarians believe that things in your pet’ environment might be a  trigger for EGC.  Since it is only a modest effort, you might consider changing the brand of your detergents, home cleaning products, pet bedding, cat litter etc. etc. Some veterinarians suggest substituting stainless steel or ceramic food and water dishes for those made of plastic.  If your cat 's condition improves, perhaps that helped, perhaps it didn't, but nothing was lost in the effort.

Progestational Drugs

These are hormone preparations associated with reproduction. The most common ones given to cats with EGC are medroxyprogesterone acetate  (Depopovera) and Megestrol  acetate (Megace, ovaban). They will, without a doubt, put most cases of EGC into remission. However their effect is no better than giving intermittent corticosteroids like prednisolone orally and their side effects are probably considerably worse. In cats, diabetes, weight gain and the potential for mammary tumors are the most well known side effect. Some times the cat's blood sugar level returns to normal when these drugs are discontinued; but sometimes is doesn't.

Cyclosporine =Atopica

This immunosuppresant drug is sometimes offered as  an alternative to long term corticosteroid medications. It is about as effective as prednisolone but, in my opinion, its potential side effects are just as serious (just not the same ones). I would reserve it for cats that, after multiple flare ups, no longer respond to corticosteroids.
You can read about Atopica here.

ps. generic cyclosporine tastes exceptionally bad.

Whenever you suppress your cat 's immune system, with cyclosporine-like drugs or corticosteroids, there is the danger of reactivating latent toxoplasmosis that could be a threat to your family's health as well as your cat. Please, no raw meat diets or hunting for cats on those products. Read about toxoplasmosis here.

Chlorambucil

Chlorambucil (Leukeran) is a drug used in human chemotherapy - primarily for people who have developed leukemia. Some veterinarians add it to a cocktail of steroids in a last ditch effort to cure cats with EGC that have not responded to other treatment. I have no experience using it.

Surgery - Rarely  The Answer

The only time I suggest that EGC affected areas be surgically removed from your cat is when they are present in its mouth, they are large, and they prevent the cat from eating. Even then, I would not consider it until all traditional medications have failed to shrink the lesions. If performed, I would suggest  cryosurgery, radiation therapy or perhaps laser surgery to shrink the lesion . With all those procedures, relapse is quite likely because the underlying problem is not addressed.

When faced with a stubborn Eosinophilic granuloma affecting your cat's cornea, surgical removal is a much more accepted treatment.

A New Home

If you and your cat are faced with a lifetime of EGC problems, perhaps you should consider finding it another quite different home or a complete lifestyle change for both you and your cat. I explained to you that there is probably a large environmental component in determining which cats develop EGC and which do not.

I once owned a cat named Bubbles. When she was about 3 years old, she developed her first bout of EGC. I had met an old veterinarian some years before who told me that a cat was once brought to him with EGC. Being busy at the time, he had his kennel boy place it in his upstairs kennel. It then slipped his mind and several weeks went by. When he finally remembered the cat and had it brought down for an exam, he found that the EGC lesions had disappeared. When Bubbles developed lip ulcers, I would place her in my second story kennels. Invariably, within a month, her problems resolved without medications. I do not know why - most likely whatever was causing the problem in her home environment was not present at my animal hospital. I am not suggesting that this works for all cats with EGC - but it worked for Bubbles.

Scientifically Unproven Remedies

When you are dealing with a problem like EGC that naturally waxes and wanes (naturally increases and decreases in severity over time)  it can be difficult to decide if improvement was due to the medications you administered to your cat or would have happened anyway on their own. These natural ups and downs of EGC cats probably explain why unproven, far-fetched or outlandish treatments sometimes appear to work. I personally have no faith in them.

Veterinarians and pet owners have announced all sorts of these EGC cures:

An Israeli vet cures her EGC cases by administering homeopathic snake venom remedies (ref)

Some vets administer alpha-Interferon and claim improvement

Some veterinarians administer gold salts and claim improvement.

Some give compounds known as "immunomodulors" that include levamisole and concoctions of homogenized bacteria (bacterins) and claim improvement.

Some veterinarians apply DMSO to EGC lesions and claim improvement.

Antihistamines And Fatty Acid Supplements

I put antihistamines and fatty acid supplements (eg EFAs,Derm Capsules etc.) here as well. I have not been impressed with the effects of either when dealing with EGC. The exceptions might be Periactin (cyproheptadine) antihistamine, which seems to have a calming effect on cats and might aid in relieving stress - it , like corticosteroids, can also give them the munchies too. Cats on a bizarre, unbalance diet that does not contain sufficient EFAs might benefit from an EFA supplement.

Will My Cat Face This Problem Again ?

There are veterinarians who will tell you that your cat 's EGC problem will not return when we find the underlying cause or causes and eliminate it from your cat 's life. Unfortunately, in the majority of cases, we will never really be certain what those underlying causes are.

In some cases, extensive testing and veterinary specialists can discover one or more underlying causes. But in many more cats, multiple changes you make in your cat 's lifestyle leave those problems behind - whatever they may have been.
Veterinarians cannot predict which cats will have a single bout of EGC and which will have many throughout their lives. We do know that those that have had more than one attack are more likely to have many during their lifetime.