How much basophils are high enough to be dangerous is analyzed according to the specific condition, e.g., true erythrocytosis may be mildly elevated up to 1×10^9/L. Normal value of basophils: Percentage value is 0~1%, absolute value (0~0.1)×10^9/L. Basophilia is considered when the percentage of basophil count is >1% or the absolute value is >0.1×10^9/L. 1. True erythrocytosis: basophils may be mildly elevated (1 x 10^9/L). The prognosis is generally good. The disease develops slowly and can last up to about 20 years without complications. 2. Chronic granulocytic leukemia: mild anemia and leukocytosis may occur with the development of the disease. The absolute value of basophils and eosinophils can be up to 2%~3%, sometimes up to 20%~90%, suggesting a poor prognosis. The median survival period after chemotherapy is 39～47 months, and the 5-year and 8-year survival rates are 25%～35% and 8%～17% respectively, and individuals can survive for 10～20 years. 3. Basophilic leukemia: Rare. The number of basophils can be abnormally increased, usually >20%, and most of them are naïve. Acute type of this disease can be accompanied by hemorrhage, histaminemia, etc. It is not sensitive to chemotherapy and has a poor prognosis, often dying of cerebral hemorrhage. 4. In addition to the above diseases, allergic or inflammatory diseases such as urticaria and ulcerative colitis can also cause mild to moderate elevation of basophils, and the prognosis is generally better. It is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or therapy.