What are the causes of elevated eosinophils in a feline?

Updated July 20, 2017

Eosinophils in felines are small, rod-shaped white blood cells formed in the bone marrow that regulate tissue parasites and control allergic and inflammatory responses. The normal range for eosinophils in the blood of felines is 100 to 1,200 per microliter, according to the Cornell University College of Veterinary Medicine. Although the causes of elevated eosinophils, or eosinophilia, in felines are numerous, certain medical conditions are more likely to result in eosinophilia than others.

Eosinophilic Granuloma Complex

Eosinophilic granuloma complex is a group of skin lesions caused by an allergic reaction. The lesions come in three forms: eosinophilic granulomas, eosinophilic plaque and indolent ulcers. Eosinophilic granulomas are raised yellow or pink nodules that mostly appear on the rear legs, in and around the mouth and on the face of adolescent kittens. Eosinophilic plaque is raised, red, round itchy patches on the belly, inner thigh or throat, which can become ulcerated. And indolent ulcers are red, glistening erosions on the upper lip and tongue, which can interfere with a feline's ability to eat. Female cats are particularly prone to eosinophilic granuloma complex. Treatment includes corticosteroid prescriptions and removal of any allergens that may be causing the complex.

Feline Asthma

Asthma is another cause of elevated eosinophils in felines. Just as with humans, feline asthma involves an inflammation of the airways that results in coughing and wheezing, sometimes to the point of respiratory distress. Cats ages 2 to 8 are most likely to develop asthma, with females twice as likely as males to have it, according to An asthma attack occurs when the tissues lining the bronchial walls become inflamed due to allergens, viruses or infections and produce more mucus. The inflammation and mucus then cause the airways to constrict. Similar to human asthma, feline asthma can be triggered by exposure to smoke, insect and hairsprays, dust, perfumes, ragweed, certain foods and feather pillows, as well as bacterial infections and viruses. Treatment includes limiting exposure to triggers, and inhalation therapy with albuterol and corticosteroids. Prednisone treatments are also given to cats with severe asthma.

Inflammatory Bowel Disease

Cats can suffer from inflammatory bowel disease just like humans. The symptoms are similar, including chronic vomiting and diarrhoea. This gastrointestinal problem can lead to increased eosinophils in felines and if left untreated can result in dehydration and even death. Middle-aged or older cats are more prone to inflammatory bowel disease, which is caused by inflamed cells in the lining of the digestive tract. Food sensitivities contribute to the inflammation, and a change in diet is usually part of the treatment along with the prescription of corticosteroids. Although inflammatory bowel disease can't be cured, it can be kept under control with proper treatment.

Flea Allergy Dermatitis

An allergy to the saliva from flea bites is another common cause of eosinophilia in felines. Flea allergy dermatitis causes itchy skin, which can lead to secondary skin infections. Felines with this allergy actually have few fleas on their bodies, because the itching causes excessive grooming, which dislodges the fleas. Cats that live in areas with humidity of 75 to 85 per cent and temperatures of 18.3 to 26.7 degrees Celsius are more likely to have flea allergy dermatitis, according to In addition to extreme itching, felines with flea allergy dermatitis will chew on their tail, rump and legs, and can develop oozing lesions and hot spots. Steroid treatments, antibiotics and antifungal drugs are used to treat flea allergy dermatitis, but an effective flea control must also be used to keep fleas at bay.

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