You post is too general and vague for any real comment. But, I don't associate getting "hot" or "itchy" as heart rhythm related...I could be wrong.
As for a little fast, what is that specifically, 70 bpm, 80 bpm, 120 bpm...?
I am allergic to shellfish, but wasn't always. One time after I ate it, I got "itchy." Now if I eat it I start to swell up like Will Smith in Hitch. Did you eat something like shellfish or nuts? An allergic reaction will make your heart race as well. Getting hot may be from heart speeding up. Just a thought.