The most common causes of high eosinophil 8% include allergic diseases, parasitic infections, etc. It is also seen in tumors and malignant diseases of the blood system. Eosinophil is a kind of white blood cell classification, the normal value of eosinophil count ranges from 0.02~0.5*10^9/L, and the normal value of eosinophil percentage ranges from 0.5~5%. 1. Allergic diseases include allergic asthma, allergic rhinitis, atopic dermatitis and drug allergy. 2. Parasitic infections including schistosomiasis, hookworm, etc. High eosinophils in these patients are temporary and can return to normal after the primary disease is cured. 3. Clinically, malignant tumors (intestinal cancer, lung cancer, etc.), hematologic malignant diseases (leukemia, lymphoma, myeloma, etc.) and other diseases can also lead to high eosinophils. If eosinophils are obviously elevated and persistently elevated, it is necessary to be alert to the possibility of eosinophilic leukemia, and relevant examinations should be completed to clarify the diagnosis and active treatment. It is recommended that the patient should consult a doctor in time to identify the cause of eosinophilic leukemia, and then treat the cause of the disease.