Thanks everyone who took a look and responded. After watching the rash last night, we are pretty sure they were hives. After I took that picture, more spots developed, and the old ones would disappear. It then spread down his legs and back. He had the same reaction to penicillin when he was one, although that time the hives were filled in, not empty circles. I'm pretty sure it was an allergic reaction of some kind, but I don't know to what. After his bath, his lethargy went away, and he was his normal self. And this morning the rash was gone! I am going to get him into the allergist to find out what's going on. He has seasonal allergies, and his ped. suggested zertec instead of clariton and prescribed flonase also. He started those new meds 2 - 3 weeks ago, so that may be a possible cause.