Hi Jan, it seems really unlikely to me that after just one dose of Diflucan that the baby broke out in hives from the diflucan. It takes a little while for the body to develop such an IgE response to a drug, usually takes a few exposures. I suppose after 5 or 6 breastfeeds while mom is on the med the baby could have mounted an allergic response. I have used a fair amount of diflucan and haven't noticed this yet. Also, the number one cause of hives in a child is a virus or bacterial infection.-Anne Eglash MD