What Could Itchy Tingling Sensation In Body Suggest?

I have had generalised body tingling on my skin on and off for years.it now happens every day.I've had allergy tests and tests for underlying causes but nothing has shown up.the tingling makes me itch all over my body and is driving me mad. I am also worried there may be something seriously wrong.I've have been to my doctor several times but now don't know where else to turn. Please help.