I can only give you an account of my upper body itch (especially my upper right arm).
I really have no idea why I have an itch, wether it's something I just have. My GP's, have no idea. I sometimes get a reminder off the missus as I don't realise that I'm scratching. Does it burn like hot needles? It's worse when I go cold and when I'm tired. But a frozen ice pack relieves it a little for a while.
I can take Pyrotin as an anti-hystamine. that seems to alleviate the itching and burning.
It could be a syptom of Diabetes, as my itch started a couple of years before my dianosis, my GP reckoned I had prediabetes for up to 3 years before.
Speak to your GP, as everyone is different, but just don't sit and scratch.