My 4 Yo Daughter Woke Up With A Rash Exactly

My 4 yo daughter woke up with a rash exactly everywhere her clothing was on Friday am...trunk and bottom. It was very itchy and irritating. Which spread to whole body by evening. Was prickly and fine and covering her closely, not sporadic or blotchy. It lessened and itching almost went away and she got a fever today...day 3...which is 102.89 and after a little nap, her head and spine ache and she's dizzy.