I have this lovely TB mare (14 years old). She has developed hives. They were all over her body. Her legs filled up and she felt awful. I was giving her 15 tabs of Benedryl to try and avoid Dex. Finally, I had to call the vet. The vet came out gave her a steroid shot and put her on a schedule of Dex. She took blood and gave me antibiotics just in case it got worse with the Dex. Never had to give her the antibiotics, but as soon as we go down to 2 tabs of Dex it comes back strong. I have taken her off the grass and just hay. Bathing doesn't help. This has been going on 2 weeks. I don't want to keep giving her Dex as she could founder on it. Even on 3 tabs a day she has hives. Help.