How To Cure Hives Causing Itching And Swelling Of Earlobes And Feet?

My 16 year old daughter was on minocycline for over 2 weeks. On Monday night she said she was very itchy, and I gave her benadryl. She woke up with hives yesterday, along with swollen fingers, earlobes, and feet. I was told she was probably having an allergic reaction to the antibiotic. She was given hydroxyzine HCL for itching and told to start prednisone this morning. When she woke up today the hives have spread even more. The medicine really isn't helping with the itching. Would a cortisone shot help?