I know how scary it can be with unknown rashes, they seem like a symptom of everything.
I had impitego, it was more crusty and yellow/pussy, (sorry, TMI I know).
I am not a doctor, but I *believe* mennengococcol (sp?) is more bruised looking.
It's interesting that it seems to be a ring around his leg, was this by chance a cuff of a pair of shorts or can you think of anything that came in contact with that area of his leg?
This website goes through a number of questions/diagnosis about rashes, but I couldn't find one that fit your little guy. http://familydoctor.org/545.xml
This is another good site I like: http://www.nlm.nih.gov/medlineplus/e...cle/003220.htm
. You can find "rash" under "R". From what I've read and the pics, it really seems like poison ivy/oak/sumac. I sometimes give antihistamine (children's Benadryl) for allergic reactions. It can apparently calm the itch if it is an allergic reaction of some sort. I hate giving medication, but if your child needs sleep, it can help.
Skin rashes can also be as a result of an allergic reaction to medication - did he take medication when he was sick?
Good luck mamma, keep us posted!