What Causes Itching On The Hand Followed By Dizzy Spell?

On three occasions now when standing up I have had an incessant itch on the back of my left hand followed by a strong bout of dizziness. As on all three occasions I had been presenting to a group of people the first time I put it down to stress or just having a meagre breakfast, but now I’m not so sure. I have had panic attacks about 10 years ago and this feels altogether different as I’m in a good place in my life with no anxiety at present.