My child has for the past week had red, itchy welt looking rashes spotted all over his legs and spreading partially to his behind. The rashes (welts) turn into bruises after a few days, and his legs are covered in them. Two days ago he started complaining of pain in one leg, and walks with a small limp. He is acting completely fine otherwise though...no fever, headaches, etc...just a normal 4 year old. What is this?? The doctor thinks it may be Allergic Purpura..but I m not convinced.