A routine blood test with an absolute value of eosinophils (EOS) > 0.5 x 109/L is called eosinophilia. Most eosinophilia is due to increased reactivity secondary to various physical diseases. 5. neoplastic diseases (leukemias such as AML-M4EO and CML, lymphomas, solid tumors and metastatic cancers); 6. other rare causes such as endocrine diseases Addison’s disease and pituitary insufficiency, GVHD and immunodeficiency diseases. The increase in EOS secondary to these diseases is usually mild to moderate. Doctors need to take a detailed medical history, including a history of recent travel, and perform relevant tests to clarify the presence of these diseases.