Will Dexamethasone cause WBC count to spike in children (6yr old)? My child was given this and his results came back 4200

Yes. Dexamethasone causes extra neutrophils to enter the circulating blood. The white counts fluctuate wildly even from hour to hour even in health.
Yes. But the count you list is well within the normal range.I would actually consider it on the lower side of normal.