I can't get too hot or I break out in hives, turn red, and have fainted in the past. It it worse now that I am in pre-menopause. I can't even control if I get hot now. I am 52 and this started in my teens. Sun heat is the hardest on me. I have read other posts on this subject, gone to a couple doctors and am coming to the sad realization that I will die with this condition without ever having a diagnosis or successful treatment for it. I am a freak of nature. I love gardening, hiking and really have been a prisoner of this condition my whole life. I am a healthy person other than this issue. I am aging pretty well, not overweight, eat right. I just can't enjoy the outdoors when it is even warm out. High 60s is too hot if I am in the sun.