My guess is HSP if they contain any spots that are more like little bruises. Along with the spots there were hives. You can see pictures in my blog on this site. This was about a month after contracting MRSA for the first time. I haven't had it since. I've heard 3% of the cf pop will experience this in their lifetime...usually associated with b. cepacia.
Another time I had hives, it was determined to be a tartrazine sensitivity or a breakout from fruit. Since I had not had a ton of fruit that could be the culprit and had had a lot of processed foods with yellow #5 we determined it was the tartrazine. I did a diet for a couple days of only a few "safe" foods for which I can not remember them all but they included sweet potatoes and chicken (with no butter). When you read about it online you will learn that tartrazine doesn't effect people right away. It builds up in the body's of some people and then when the body can handle no more it breaks out in hives. I have no idea why my body doesn't excret tartrazine like the rest of the world but I'm not alone. I avoid yellow #5 in large doses (ie. no yellow candies, no goldfish crackers, etc.)