Why Is My Dog Or Cat's Eosinophil Count High Or Low ?













Ron Hines DVM PhD

To see what normal blood and urine values are, go here

For an explanation of causes of most abnormal blood and urine tests, go here

To see how tests are grouped, go here

Your Pet's Eosinophil Count = Eos when high = eosinophilia

Eosinophils are slightly larger than the much more common neutrophil in your pet's blood. When stained with dye, they have large distinctive pink-red granules in their cytoplasm. These granules take up a particular staining agent dye called eosin - hence their name. Eosinophils are manufactured by stem cells in your pet’s bone marrow. After they leave the marrow, they stay in the pet’s blood for only a short time before moving out into its body tissues. Eosinophil numbers decreased when corticosteroid medications are given.

Eosinophils also have the ability to "eat" or engulf (phagocytize) foreign particles that ought not be in the blood or tissue into their structure.


Reasons Your Pet’s Eosinophil Count Could Be High (eosinophilia):

Allergic and hypersensitivity reactions, internal parasite infections, flea allergies, mast cell tumors and a few other types of tumors, hypereosinophilic syndromes (eg eosinophilic granuloma) in cats, Addison’s disease (along with increased number of lymphocytes), heartworm disease, allergic pneumonitis, inflammatory bowel disease (IBD). In cats with respiratory symptoms, asthma or lungworms (17-46% of asthmatic cats have higher than normal eosinophil counts). (ref)

According to a September, 2018 article in Clinician's Brief by Dr. Glenn Olah of the Winn Feline Foundation, the top causes of elevated eosinophil counts in cats are: Internal or external parasites, feline allergic dermatitis, feline asthma, and eosinophilic gastrointestinal disease. Other rarer causes discussed were hypereosinophilic syndrome, neoplasia (cancer) and paraneoplastic syndrome (pre-cancerous states). Let me know if you wish to read it.

Reasons Your Pet’s Eosinophil Count Could Be Low (eosinopenia) :

Since it is not uncommon to find no eosinophils in the blood sample of healthy pets, having none is not abnormal. But all corticosteroid medications lower eosinophil numbers as does the prolonged stresses that causes natural cortisol levels to increase. That can mask diseases that would have normally increased your pet's eosinophil count.

Complimentary Tests :

Examinations for allergies or parasites that might be the underlying cause of the increased eosinophil numbers. (blood allergy testing is worthless in pets, but skin tests can be helpful)