I have had this rash off and on since I moved to Arizona. When it comes, it always comes on the same spot on my neck and back and in the same shape every time. I have guessed it is a heat rash and it is nothing serious, since I am from Michigan and not used to growing up in the Arizona heat. It never gets bumpy or itchy. Always stays smooth, somewhat dry, shows up more the hotter it is it seems. Is this something to worry about?