Eosinophilic Disease in Cats

Eosinophilic disease is a very uncomfortable and treatable dermatological condition in cats. If you see signs of this disease, contact your veterinarian immediately.

Eosinophils are a type of white blood cell, which are an important part of the body’s immune response, assisting the body in fighting infection. Eosinophilic diseases occur when the eosinophils mistakenly release inflammatory chemicals that are meant to fight parasitic invasion when no parasites have actually infected the cat. This condition usually occurs as a result of a hypersensitive reaction to mosquito, flea or mite bites, medicine, or food, and causes severe symptoms of an allergic reaction such as itching, swelling, ulcers, oozing sores, bumps, and/or tumor-like growths.

As listed above, eosinophilic disease can come in three variations, which are eosinophilic ulcer, eosinophilic plaque, and eosinophilic granuloma. The symptoms of these versions of this disease are as follows:

• Itching
• Swelling
• Ulcers, especially on the top lip
• Oozing, infected sores as the result of persistent scratching
• Hive-like bumps, especially on the inner thighs and abdomen
• Tumor-like growths, especially in the mouth or hind legs

Types

There are three types of eosinophilic disease in cats. Cats can experience one, two, or all three of these forms of eosinophilic disease at the same time.

Eosinophilic Ulcer

Eosinophilic ulcers usually present inside the mouth or on the top lip. 

Eosinophilic Plaque

Eosinophilic plaque manifests as inflamed hive-like bumps on the inner thighs and abdomen. 

Eosinophilic Granuloma

Eosinophilic granuloma is by far the most common of the three conditions in cats. The condition causes large pinkish-yellow bumps that can appear as ulcers or tumors on the hind legs and/or in the mouth. 

The most common cause of the various forms of eosinophilic disease is a hypersensitive immune reaction to one of the following:

• Mosquito bites
• Flea bites
• Mite bites
• Antibiotics or heart medications
• Foods to which the cat is allergic

As is usually the case, your veterinarian will likely begin the appointment by asking you what symptoms you have observed as well as asking if there have been any recent changes in the cat’s diet. In addition, your vet will review your cat’s known medical history. After doing so, the vet will utilize some or all of the following diagnostic tools:

• A thorough physical examination, paying special attention to the condition of the skin and whether or not the cat has fleas or any other skin parasites or any visible insect bites
• Blood tests to determine if the cat has an infection
• A skin biopsy may be taken to determine if parasites or dermatophytes, usually skin fungi, are present.

The most effective way to treat eosinophilic disease is to address the disease with a twofold approach. The vet will attempt to determine what is causing the hypersensitive reaction, and then remove your cat from the environment that causing it or remove the offending agent from your cat’s environment. This may be attempted through one or more of the following:

• Aggressive treatment for fleas
• Keeping your cat indoors away from mosquitos
• Cleaning the cat’s coat and the living environment to remove mites, as well as treating for mites
• Prescribing a different medication if it is believed that a medication is causing the hypersensitive reaction
• Switching to a food with different ingredients

The vet will, usually at the same time, treat the secondary skin symptoms. Whether the underlying cause of the reaction can be determined, the following may be prescribed to help the cat’s skin condition to clear up:

• Corticosteroids to decrease inflammation
• Immunosuppressant drugs such as cyclosporine
• Antibiotics if sores have become infected
• Essential fatty acids
• If dermatophytes such as Microsporum canis  are present, the vet will likely prescribe fluconazole or itraconazole.

A cat’s recovery from eosinophilic disease is highly dependent upon whether or not you and your vet can determine what has caused the hypersensitive reaction. If the underlying cause can be determined and that cause removed from the cat’s environment, a positive prognosis of complete recovery is highly likely. The pet owner will need to be vigilant in ensuring that this removal of the cause remains lasting and consistent. If the underlying cause cannot be determined, the short term prognosis may still be good with treatment, but the likelihood of recurrences of itching, ulcers, sores, and bumps is likely.