I started noticing it many years ago. When I would scratch my skin it would welt and then everything around it itched and by the time I stopped scratching there was a huge patch of my skin covered in lifted, red, hot, and tingling welts. The severity comes and goes, but trying on wedding dresses was interesting. Everytime I took one off I had the outline of the bodice whelted onto my body. Ever since having my son it has not been as severe unless I get stressed out or sick.
More information on this skin condition can be found at the dermatographism page.