Suggest Remedy For Hives All Over The Body

My husband has urticaria and he has never has any allergic responses to anything. He is 53. I have notices that since Feb he has had problems getting over a simple sinus or chest cold-- meds help it but it is always coming back. We are now doctoring with an allergist but he got a long/quick acting shot on Monday and did a breathing treatment and taking predisone of 10mg (20mg each day worked) but they are weaning him. He has hives already today. Gets it all over his body. Everywhere. Any ideas?? We know that its hard to figure out. 4 viles of blood were drawn and we can cross off the thyrod and outside enviromental. He remembers the beginning because he works outside for the county highway and has been doing it for 33 years. He called and said he felt like he had playrisee??(spelling) Chest pressure and deep breathing pain and went to the doctor which he never does-- things have gone down hill from there. They did do an ekg and heart is fine