im 17 turning 18 and ive had this recurring rash for at least 3 or 4 years, it comes and goes randomly i have no idea why it happends, but antihistamene controls it perfectly. at first i thought it was a heat rash, then i got it in winter, so then i thought it was stress but when i was stressed during exams i didnt get it, theni thought it was some type of plant, but i get it at home and random places. the rash is irritating and uncomfortable and comes up when i scratch it it is usually starts on my forearms then my back, face, legs n stomach will get extremlty itchy.   i have no idea, im assuming it is a symptom of something going wrong in the body?