Please help!! Is my baby allergic to formula??

Leeah • 20 • mama to a baby girl • married to the love of my life •

My daughter has been ebf until my supply tanked overnight and I supplemented for the first time with formula this morning. Now however, she has an under the arm fever of 99.2 and she is broken out. Her skin is super super red. I’m really worried. Please help! Do I go to the Er for a fever?