Ive Been Extremely Itchy The Last Three Days. The Kind

Ive been extremely itchy the last three days. The kind that so unbearable that it makes you cry and I leave welts from scratching. It started with my palms, then my feet, and now it's everywhere. I can't focus. I tried Benadryl cream, helped a little. I took Benadryl liquid gels (2), and it didn't help at all. I don't know what to do. There is no rash, and I can't figure out what's going on. Please help!