serious question..pediatrician is closed right now..husband at work...I'm not to extremely…

serious question..pediatrician is closed right now..husband at work...I'm not to extremely worried...I just Google everything..although I hate it cause it freaks me out more...so ##1 what age do kids get chickenpox?..my son is 2 he doesn't have a fever he isn't sick nothing I thought it was a heat rash..cause it was tiny and only by his tummy..he gets very sweaty in the heat...we have been in our cool house.. so no heat...I use the same detergent /laundry stuff since he was born..idk what it is...if its still there by tomorrow..I'm going to make him an appointment... might by exema lotion tonight...