A: It doesn't necessarily correlate with high cortisol for everybody. High cortisol could be a reason for some people. For others it might be just something that they've consumed. For example, if you take a niacin supplement it may cause flushing. Sometimes GABA can cause that for some people. Also, I'm not sure if it's flushing or hives, but I would also consider looking into Blastocystis hominis. That's a common parasite that's associated with causing Hashimoto's. About 30% of people with Hashimoto's have it in my experience, and it can cause chronic hives and urticaria, which is similar to flushing.