Eosinophils are a type of white blood cell with a normal value of (0.05-0.5)x10^9/L. Eosinophils can be lowered by cold, starvation, mental stimulation, and labor, and are usually lower during the day and higher at night, but generally fluctuate within the normal range. Low eosinophils may occur in the early stages of typhoid and paratyphoid fever, in stressful conditions such as major surgery and burns, or after long-term application of adrenocorticotropic hormones due to the stress response of the body, but are generally of little clinical significance. If patients experience a continuous decrease or even disappearance of eosinophils during the recovery period of the disease, it may be caused by the aggravation of the disease, and patients are advised to review the disease in time for appropriate treatment. Clinically elevated eosinophils are more clinically significant and often indicate that the patient has allergies, parasitic diseases or eczema, dermatitis, etc. In addition, certain blood disorders, malignancies and other diseases may also cause patients to develop elevated eosinophils. If eosinophils continue to decrease or even disappear, it is recommended to go to a regular hospital to improve other examinations and make a comprehensive analysis and diagnosis through examinations, signs and symptoms to avoid delaying the disease.