What causes elevated white blood cell count in children?

An elevated white blood cell count may be a normal response of the body fighting a disease or pathogen infection. However, persistently high white blood cell counts may indicate an underlying disease or pathological inflammatory reaction. There are many possible causes for elevated white blood cell counts in children, including common infectious diseases caused by bacteria, viruses, fungi, and other pathogens; allergic reactions such as allergic rhinitis and asthma; immune system abnormalities such as autoimmune disorders; and hematological conditions such as anemia and leukemia.