I have actually developed a full on heat allergy over the last few years. If a particular area on my body gets exposed to too much heat, such as a too hot oven on my arms or the sun on my legs I can get a rash and even break out in hives. If I get too hot overall I'll have a full on allergic reaction. I start to get lightheaded first and I can feel my blood pressure drop. Then if I don't get cooled off fast in the next 2-3 minutes I'll start to have trouble breathing. I won't leave my house in the summer if the temp is over 80 or so without a lunchbag full of ice packs and unless it's a dire emergency I never leave my house between noonish and about 5 or 6 in the evening in the summer.

And this all started the first summer I had pain in my ankle. I never really connected the two. I do have other health issues. Celiac disease and CRPS topping the list, but a lot of other little things that just compound to make my life difficult. I've wondered often if my heat problem is related to my issue with high histamine foods, but that has been slowly resolving while the heat problem gets continually worse. I don't have any advice, just wanted you to know you aren't alone.