Eosinophils are a kind of white blood cells, blood tests can be seen, the normal value is 0.005-0.05. Eosinophilia, most often seen in skin diseases, allergic reaction diseases. For example, allergic bronchial asthma, urticaria, atopic dermatitis, eczema, etc., but also seen in scarlet fever, splenectomy and so on. Eosinophilia is seen in typhoid fever, paratyphoid fever, and the application of certain adrenocorticotropic hormones. Eosinophilia and hypereosinophilia are good references for clinical diagnosis of the disease.