What Causes Redness And Warm Sensation On Toes Of A Child?

i have a 2 year old son who has one foot all 5 toes are red and warm to the touch while other foot has only one tow really red but cool to the touch. doctor has rolled out the flue and its not due to ear infection nor the trought. doctors give me a blood work paper to get microbiology and hematology blood work. what can it be for a child....