I Had Large Red Swatches Of Skin On My Back

I had large red swatches of skin on my back and torso with smaller hives surrounding the larger red swatches of skin. It felt itchy and I took Benadryl. The itching felt like pins and needles. I woke up and my face was swollen. It has been 20 hours later and the skin has cleared up but now the redness has traveled to my lower legs and arms/wrists.