Feeling Pain, Red, Hot On Feet, Hands, Arms And Leg. Painful Swelling. Took Benadryl. What Should Be Done?

I have been experiencing painful, red, hot welts on the bottom of my feet , hands, arms and legs. They come on all of a sudden and the swelling is painful. The welt can stay for 2 days, but changes to a very painful bruise that will last up to a week. I m not allergic to anything and have been experiencing this for a month. I thought it would resolve itself. I ve tried Benadryl without success and cold packs. What should be my next move? Thank you.