Eosinophils Eosinophils Equine eosinophil Eosinophils are produced in marrow, circulate in blood for a few hours, and migrate into tissues where they survive for several days. Corticosteroids decrease blood eosinophil numbers but increase the marrow pool of eosinophils. Increased numbers of circulating eosinophils may be seen in hypersensitivity reactions, as with certain forms of parasitism and allergic conditions. The presence of mast cell tumors in an animal may also be associated with eosinophilia.
Basophilia sometimes occurs concurrent with eosinophilia.