sounds like 5th's disease. It is a virus that goes around like hand, foot and mouth disease. Both of my children had it over the last 3 weeks. Basically they can have it for up to a month before you even know they have it. Some children get fevers and some do not. Once the rash has broken out and the fever is gone, they are no longer contagious. Many do not even know they have it and then they see the rash and it is no longer contagious. It takes about a week of the rash to go away and can come back up to two weeks off and on. There is nothing you can give them b/c it is viral. We rubbed hydrocortisone b/c my kids said it itched a bit but really there is nothing you can do. Just wait it out. If you see him have trouble breathing or anything other than the hives or fever, take him in b/c it then could be more serious and could constrict his breathing. Allergies or sickness can do this but it sounds like 5ths disease...or "slapped face syndrome" is the nickname.