My daughter is running a low grade fever and now she is covered with a rash. What could this be?

We could sit here all day saying what it could be.
We don't know if she's 6 weeks/months/years, history, vaccinations, what her temp is, what the rash looks like, where it is, allergies, what she has eaten, and that's just for starters. This is a question for her doctor.

Put her in a bath tub on warm the hotter the better for at least 30 minutes and her rash should go away