Can Macrobid Cause Allergy?

I was treated for a UTI on 4/9/11. I was put on a 10 day course of Macrobid. On the last day the palms of my hand started itching. By the next day it was generalized all over my body. On 4/22/11 I saw my primary who put me on prednisone 10mg for 5 days, he also gave me hydroxyzine for the itching. I took this and it seemed to have gone away. Well its back. Sometimes they are generalized hives, sometimes they are like red elevated lines on my body. It s weird. It can be there and gone in 1 hour. Then back in another part of my body. It will respond to benedryl (sometimes). The hydroxizine kicks it but really gets me sleepy. I m using hydrocortisone cream and it does help. I have an appointment with an allergist this friday. I can t help wondering if this is the macrobid or something else. Do you have any imput.