What Causes High Fever And Hives On The Body?

my daughter, 16, started feeling hot around 3 hrs ago, at which time she started noticing hive like rash. her temp currently is 101.5. temporal. no numbness/tingling around the mouth. she does have blankets on, but has ice packs in her armpits and on forehead. she had an iud inserted in March, no complaints of vaginal pain/discomfort routinely. some spotting intermittently. she has also been getting boils on her inner thighs and buttocks within the past 3 wks. for the first boil she received atb tx of Bactrim/Keflex. on her last day of atb (day 10) she developed hives all over her body. she was prescribed prednisone, which of course worked well within 48 hrs. she noticed two more boils approx. 3 days ago, and tonight the situation explained in top line...thoughts?