Higher than normal white blood cells (WBCs) in a child means infection or inflammation. Also, leukemia is in the differential diagnosis. Leukemia is a cancer in the blood producing huge number of WBCs. Please, check with the pediatrician who knows and treat oncological diseases, preferably a hematology / oncology. Thank you.

Depends on the type of white cell involved. May be reactive to some other situation (infection, allrgy, inflammation) or more serious.,