Low white blood cell count refers to the number of white blood cells in the peripheral blood below the normal range. In clinical practice, there are various causes of low white blood cell count, the common ones are: i. Infectious factors, seen in gram-staining negative bacillary infections as well as viral infections, such as typhoid and paratyphoid bacillary infections, influenza virus, rubella virus infections, etc., may cause the condition of lower white blood cell count. Second, certain blood system diseases, most commonly such as aplastic anemia, myelodysplastic syndrome, paroxysmal sleep hemoglobinuria, etc., can cause a decrease in the white blood cell count. Third, certain drugs cause, such as metronidazole, tinidazole, certain anti-inflammatory painkillers such as fenbendazole, etc., can cause a reduced white blood cell count. When patients receive radiotherapy or radiochemotherapy, the damage to hematopoietic stem cells caused by radiotherapy and chemotherapy can also cause low white blood cell count, especially after high-dose radiotherapy and chemotherapy, the white blood cell count can be seriously low.