I Get Rashes At Random Times I Have Done A

I get rashes at random times i have done a good diet but no answers from that I'm aware that I'm allergic to flu medication and need to do a skin test but these rashes appear randomly. I'm always getting itchy. I think I also have extra heat in my body like internal heat that may also be related if I'm not mistaken. Another thing I'm concerned about is that I have a line on my thumb nail brownish/black and read something about it unintentionally which had something to do with cancer, I'm not sure if that's correct but cancer is in my family should I be worried?