Hives from lactase?

A couple of weeks ago I woke up with hives on my legs and lower abdomen.  As the day progressed, the hives migrated up onto my chest, shoulders, and arms, and then my hands swelled up to the extent that I had to have my wedding ring cut off at the doctor's office.  Luckily, this all went away after taking Benadryl for three days.
The only thing I did differently was I tried some lactose-free ice cream the night before that has lactase in it.  Is there such a thing as an allergic reaction to lactase?  Last week, I tried a small amount of the ice cream and within 4 hours I had a couple of hives on my legs.