I've always had a clear back and chest. But last few months my chest and sometimes back will go red and blotchy. Not a spot as it don't have a head or anything but red raised bumps. My chest was like this before and I sat in the hot sun for a few hours and it disappeared and was fine and clear. Then obviously the sun went again and it was raining for a few weeks because England weather is crap. So it came back. Had  little sun today so sat out in it and only for about 20 mins not 3 hours and it wasn't as hot as last times sun. But yeah this is my chest. I don't think it's heat rash as the sun seems to help it. But what is this ? Had this on and of for months now sometimes not as bad as this. I jus wanna no what it is and what could be causing it ? Plz help. A lot more red and blotchy in person. And get it on shoulders.