itchy rash + spreading

Hi. My boyfriend is a track athlete. He recently competed in very hot weather in NE California for three days. Also, he has been under some stress. On his way there (in his own car) he began to get some itchy bumps on his forearm. He developed an itchy rash all over his torso (front and back). It has started to clear up in his chest (a week plus later) but has spread to arms, and a little to face and legs. Cortisone seemed to irritate it more. Tried calendula lotion - did not much. Also, has been taking benedryl pills, but not much relief. Its really itchy!! HELP??