Strangely swelling hand that turns red.

Patient: Occasionally my right hand turns red, becomes really hot to the touch, tingley, swollen and a bit itchy with small lumps sometimes developing under the skin. My whole hand feels really hard and stiff.When it fades after a few hours it leaves my fingertips feeling bruised and tender. The only relief I’ve found is subjecting my hand to very cold water which sometimes returns it to normal after a while.This has been happening for a few years now but only ever occurs when I’m at the computer and only the right hand.Any ideas? It’s starting to get quite annoying.

Doctor: