Baby has chronic hives?

I am waiting on my dr to call me back to hopefully get a refferal to an allergist or dermotoligist. In the mean time, I am wondering if anyone else has dealt with this. My son who is 11 months has been having hives show up for about 6 weeks now. I took him to an urgernt care a month ago. He told me it was an allergic phenomenon & prescribed prednisone. Hives still returned but I thought it was an eczema flair up. The hives returned & I took him to our family dr 2 weeks ago. That's when I learned it was actually hives. She said it should clear up with benadryl. I also eliminated dairy & wheat from his snacks. Switched to soy formula for his supplement feedings when I don't have enough breast milk. Wash his clothes in free & clear & don't use fabric softner. Don't use soap in his baths. Use Aveeno lotion, Aveeno eczema cream, or aquaphillac ointment. I took all polyester outta his clothing (no fleece sleepers, no sweats, no fleece blankets). We have no pets. The dr put him on prednisone last Thursday & he had his last dose on Tuesday. The hives showed up yesterday, ONE day after being off of prednisone. Has anyone else dealt with anything like this in the past? What did it turn out to be that your baby was allergic to?