Child with cold and a splotchy rash

My 6 year old has has a cold for the past few days along with everyone else in the house but today she woke up with an angry looking rash all over, there's a big splotch on her cheek and on her knees elbows ankles, and the rest is just spread out over her body but not as dark or angry as the big splotches. She's itchy too.. It's not chickenpox I know that.. She's up to date with all her vaccinations... Any mommas have any ideas? We're going to the dr at 2pm..