It is listed as one of the possible
side effects of the drug. Vaginal
itching and discharge is also a listed
side effect as also rust or dark colored urine.
ref:http://www.drugs.com/macrobid.html
Hives are red, itchy welts or swellings on the skin that often come in clusters. Hives can appear anywhere on the body, cropping up either in one small area or covering large patches of skin. They most often occur as part of an allergic reaction.