Eosinophils are a type of white blood cell that can kill bacteria and parasites in the body, as well as participate in metabolic and immune reactions in the body. A high percentage of eosinophils during routine blood tests usually indicates the presence of allergic diseases or infectious diseases. In this case, it is recommended to go to the hospital in time to get a clear diagnosis and give appropriate treatment, and the eosinophil percentage will return to normal after the disease is cured. Allergic diseases: such as bronchial asthma caused by allergies, mainly due to allergic substances into the body to stimulate the body’s metabolic reaction, and eosinophils participate in the metabolic reaction, so there is an increase in the percentage of white blood cells will be high, the patient will also be accompanied by cough, diarrhea and other symptoms. In this case, it is necessary to avoid contact with allergens such as pollen and seafood, and also to treat the primary disease. In the case of bronchial asthma, drugs such as salbutamol and budesonide can be given for treatment, and antihistamines such as loratadine can also be given for treatment. Infectious diseases: 1. Fungal dermatosis: It may be due to the infection of the causative organisms into the body to stimulate the body’s immune response, there will also be a high percentage of eosinophils, accompanied by rash, itching and other symptoms. Patients need to follow medical advice to use drugs such as chloriodoquinoline cream for treatment; 2, parasitic infectious diseases: such as roundworm, schistosomiasis and other diseases, mainly due to parasitic invasion of the body will cause an immune response, resulting in a high eosinophil percentage. For roundworm patients, deworming drugs such as albendazole can be given for treatment. For schistosome patients, drugs such as praziquantel can be given for treatment. Other diseases: 1. Hodgkin’s disease: mainly because the tumor may stimulate the body’s immune response, thus causing a high percentage of eosinophils. In this case, patients can be given glucocorticoid injections, or photochemotherapy such as ultraviolet light for treatment; 2, other diseases: such as scarlet fever or primary adrenocortical insufficiency, scarlet fever due to group A beta hemolytic streptococcus infection can activate part of the complement, which causes eosinophil increase, at this time need to give penicillin or erythromycin and other drugs for intravenous injection. The reason for high eosinophils due to primary adrenocortical insufficiency is not clear, but it may be caused by the immune response caused by the infection entering the body, which can be treated with glucocorticoids or hydrocortisone.