What Causes Redness And Itchy Skin On Arms, Legs And Upper Chest?

Okay, I have been getting itchy skin and in the areas of my arms, legs, upper chest, back of neck, face. I get redness, red bumps with welts. Its a horrible itchy sensation. It all of a sudden goes away and all the redness and red bumps clear and then will flare up again. Is this an allergy or maybe something else.