Eosinophils are a component of white blood cells, which have the function of killing bacteria and parasites. In general, the danger of high eosinophil ratio is caused by the primary diseases that cause the index to increase, such as allergy, parasitic infection, eosinophilia and other diseases. 1. Allergy: mainly due to the patient’s exposure to allergens. Allergy can occur in many tissues and systems, such as the respiratory system, digestive system, skin, etc., and its clinical manifestations are different in different systems, such as asthma, etc., which can even be life-threatening in serious cases. 2. Parasitic infections: The clinical manifestations are different due to the different kinds of parasites and their parasitic sites. If the parasites stay in the body, they may cause symptoms such as partiality and periumbilical pain. 3. Eosinophilia: it may cause clinical manifestations such as rash, fatigue and diarrhea. There are many other causes of high eosinophils, so it is recommended to go to the hospital in time to get a clear diagnosis and treatment under the guidance of the doctor.