What Causes Swelling In Hands And Feet, Itching And Random Patches?

For the past 3 days ive had some odd symptoms including but not limited to: hands and feet very swollen, itchy, and prickly, random patches of small itchy bumps all over my body (including my scalp) and when they are scratched, it turns into huge welts/hives. Ive tried benadryl, hydrocortozone cream, ice packs, and even went too the walk in clinic today and they gave me a couple shots of medicine and a precription of prednisone. I haven t had any new foods, cosmetics, etc....I did buy some second hand clothing but have since washed everything and my symptoms have not gotten any better, actually worse..please help with any information. Thank u so muchh!!