Hypereosinophilia is an elevation in an individuals circulating blood eosinophil count above 1.5 x 10 9 /L. This disorder is distinguished from 1) eosinophilia, which is an elevation in this count above normal levels of 0.5 x 10 9 /L but below the hypereosinophilia cutoff level and 2) the hypereosinophilic syndrome, which is a sustained elevation in this count above 1.5 x 10 9 /L that is also associated with evidence of eosinophil-based tissue injury. Informally, blood eosinophil levels are often regarded as mildly elevated at counts of 500–1.500/μL, moderately elevated between 1.500–5.000/μL, and severely elevated when greater than 5.000/μL. Elevations in blood eosinophil counts can be transient, sustained, recurrent, or cyclical.
Counting of eosinophils in human blood typically ranges between 100-500 V / mm. The content of these levels is the result of a balance between production of eosinophils in bone eosinophilic cells in the bone marrow precursors called some EOS and emigration of circulating eosinophils from the blood via post-capillary venules into the tissues. Eosinophils constitute a small percentage of peripheral blood leukocytes are usually less than 8%, have a half-life in circulation of only 8-18 hours, but persists in tissues for at least several weeks.
Eosinophils are a form of terminal differentiated granulocytes, their function is to neutralize the invading microbes, primarily parasites and helminthes, but some types of fungi and viruses. They are also involved in transplant rejection, graft versus host disease, and kill tumor cells. In carrying out these functions of eosinophils and the release on demand of a number of toxic reactive oxygen species, and they also release on-demand Arsenal of preformed cytokines, chemokines, growth factors, lipid mediators and toxic proteins. These funds are used for the organization of a reliable immune and inflammatory responses that destroy invading microbes, foreign tissues, and cancer cells. When excess and activation, which occurs in some cases, hypereosinophilia and to a lesser extent, eosinophilia, eosinophils can knock them of active forms of oxygen and equipment of preformed molecules relative to normal tissues. This can lead to serious damage to such organs as the lungs, heart, kidneys and brain.