I don't know if anyone has ever experienced this but I found it quite odd. I have certainly worked out before, but today I worked out for about 30 minutes to help my joints and i broke out into a rash over my knees and my forearms. I know you can get a rash when exposed to heat but I didn't know if you could while excercising because your body is heating up. Please help me! I found this very strange.. Can lupus cause this?