What Causes Growth Of Hives On Face After Taking Prednisone?

my friend who is female and 26 has a cold and took walgreens brand nyquil yesterday and today has swollen hands and feet and hives. her doctor prescribed prednisone and she called me and said her hives are worse and on her face. i told her to ask the pharmacist and she said she is probably allergic to prednisone. i am concerned because she has an asthma (and a single mother of a 10 month old baby). what do you think?