question: 5 year old has rash on lower back and buttocks that is red, dry and warm to touch. It looks exactly like a sunburn. Had fever when rash started up to 104 and congestion/runny nose/cough. Fever now gone. Been treating with benadryl and cortizone cream. After 3 days no change. Now he is refusing to walk but can t express any specific pain . Will only stand on tip toe. Dr baffled...any ideas what this could be?