the exact same thing happened to me a few months ago. I was just rollin at the skatepark, and both my crotch and the top of my head started to become very itchy. it eventually got so irritating that i just left and went to a gas station bathroom to see what was going on down there. I found that the itchy hives were spreading up my stomach, and starting to appear on my face. i freaked out, bussed home, by the time i got there i was red, and my entire body minus lower legs was covered in hives. i took a bunch of benadryl, went to the clinic. they asked if i had eaten anything different or taken medication, and they still couldnt figure out what the problem was. they started to go away once the benadryl kicked in, and within about 4 hours they were completely gone. not saying that will happen to you though, i'd go to a clinic if they dont start going away soon.
