Suggest Remedy To Get Rid Of Itchy Welts On Leg

hi i have a purplish red welt on my leg that itches and its spreaded to back of my knee i have like 3 places on back of my leg and on my buttocks. The welts dont alway itch and when they do its intense and i seem to have a new spot. seems like they usually start to itch after being out in the sun or getting very hot.