Wouldn't the hives be a good indication of an allergic reaction? Also, the speed in which the body was covered in hives and blotches makes me wonder about allergies. Not all allergic reactions are as severe as an anaphylaxis type reaction. Now, that's not to say that envenomation didn't occur. It may be that both reactions are occuring together.

Those are my semi-educated thoughts having dealt with quite a few allergies in my family....